kimchi & kraut

Passive House + Net Zero Energy + Permaculture Yard

Tag Archives: greenbuilt homes

Our Energy Bills

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The Logic Behind the Effort and Added Cost of Passive House

Passive House, as a building strategy, requires meticulous air sealing, along with ample amounts of insulation, carefully placed to eliminate or reduce the impact of thermal bridges through the building envelope. Once the air barrier of the building has been established, it requires mechanical ventilation to meet IAQ needs, along with high performance windows and doors to avoid undermining all of the air sealing and insulation.

Air sealing, water proofing, and thermal elements come together around a high performance window.

All of these elements together, if successfully managed and implemented, should achieve a building that requires significantly less energy to operate and maintain at comfortable temperatures than any conventionally built structure of similar size and shape.

The Visitor enjoying some early morning solar heat gain through our kitchen window.

With a ‘conservation first’ approach (i.e. extensive air sealing and insulation), the goal is to reduce total heating and cooling demand as much as reasonably possible (while maximizing occupant comfort), with the possibility of adding renewables like solar or wind as mostly an afterthought to further reduce, or eliminate entirely, the remaining energy demand of the structure. It also typically means going all electric, so in our case it meant no natural gas (the normal fuel source in our area for a furnace and a hot water tank).

So far, our 11 panel 2.9 kW system has been averaging between 3,500-4,000 kWh of solar production per year.

A Passive House structure, by design, should use significantly less energy than any conventionally built counterpart of similar size and shape. This includes lighting (normally assumes only LED fixtures will be used) and other plug-in loads (e.g. Energy Star appliances), as well as hot water (typically a heat pump hot water tank, or a newer product like Sanden or Chiltrix).

Unfortunately, these loads are relatively ‘baked-in’, even for an existing, conventionally built home. For instance, a hundred year old home could switch all of their light fixtures to LED bulbs, replace old appliances with new Energy Star rated models, and change out a gas-fired or a conventional electric hot water tank to a high-efficiency heat pump model. In effect, they’d have pretty much the same reduction in energy use as a brand new certified Passive House of similar size and layout for these particular sources of energy demand. As a result, the real opportunities for driving down energy use in a Passive House are in the heating and cooling loads (mainly due, of course, to the extensive air sealing and insulation levels).

On most days the 15,000 Btu head in our kitchen and family room handles all of the heating and AC needs for our entire house. We have two additional heads in our bedrooms (9k and 6k Btu respectively), but they’re rarely used apart from the coldest and hottest days of the year.

Although there has been some moving of the goal posts as the Passive House programs have evolved over time, they remain challenging targets to meet.

Here are the current PHI requirements according to Passipedia: Passive House Checklist

In the case of PHIUS, the requirements have gone through several iterations, for instance, PHIUS+ 2015, PHIUS+ 2018, and most recently a fairly dramatic change to a prescriptive track to seek certification with far less onerous levels of paperwork and data collection required.

Overall, regardless of which model is pursued, PHI or PHIUS, the intent is to dramatically reduce the overall energy use of buildings by emphasizing the importance of air sealing, insulating to levels that exceed current code requirements (in most cases), along with quantifying things like thermal bridges, heating and cooling demand, and peak heating and cooling demand. The issue of energy demand or energy use is further complicated by the distinction made between Primary/Source and Site Energy.

Additionally, there’s been a growing consensus regarding the need to incorporate renewables in these building strategies, both in terms of financial feasibility and in terms of further reducing (or even canceling out altogether) net energy demand. And while it’s true that Net Zero is fairly straightforward to achieve (assuming needlessly large PV arrays are not utilized as a short-cut), it does require a commitment to meticulous air sealing and quantities of insulation that, along with the in-depth energy modeling, unavoidably add cost to any construction budget.

Zehnder ERV, Rheem HPHW tank, radon pipe with fan, and battery back-up sump pump. Elements that support proper moisture management, IAQ, and HVAC needs.

The opportunity for significant energy reduction also correlates with the size of the project. Because of form factor ratios, the larger the project (assuming a compact form is mostly maintained) the more energy a structure stands to conserve. This is why larger institutional, multi-family projects, or corporate-sized projects stand to be the biggest winners when it comes to the purported benefits associated with Passive House energy conservation.

Outdoor heat pump compressor after the snow, but before the worst of the 2019 Polar Vortex.

If executed properly, low energy demand will mean considerable financial savings. These savings are cumulative, year after year, rather than just a one-off initial price break, with the added potential to increase should energy costs go up.

In addition, there is the potential for less upfront expenditures for HVAC equipment (less heating and AC demand — at least in theory — means smaller and more cost-effective equipment required). In our case, in climate zone 5, where we get cold, dry winters and hot, humid summers, this didn’t prove to be the case. Combining the cost of our heat pump and ERV reflected roughly what we would’ve paid had we built a conventional home with a high efficiency gas furnace with a humidifier attached (fairly typical system in our area). Either way, it would constitute roughly a $20,000 expenditure for a house under 2,000 square feet. The level of indoor comfort, however, should be vastly different between a conventional and a Passive House build.

Even though occupant behavior can derail some of these projected performance outcomes, assuming that homeowners or tenants are reasonably educated on the best way to enjoy and benefit from the Passive House details, especially the HVAC systems (normally this means commissioning units and then mostly leaving them alone in terms of settings), this should not be a stumbling block for most builds.

While all of this becomes more challenging with a smaller, more compact build like our 1,500 square foot single-family home, the possibility of significantly lowering energy demand is no less real, along with the cost savings. Not to mention the level of occupant comfort, which I personally feel is the main selling point of the Passive House building principles.

Some Background Information on Our Home

A quick summary of our build would include our blower door score of 0.2 ACH@50 (106 cfm@50), along with the following R-values for the structure:

R-16 Below the basement slab

R-20 Exterior of the basement foundation

R-40 Exterior walls

R-80 Attic

In 2019, our first full year of occupancy, with three of us (my wife, daughter, and myself) we had a total of just over 11,000 kWh of energy use. This included lighting, all other plug-in electricity demands (appliances, TV, computers, charging cell phones etc.), along with our HPHW tank and all of our heating and AC needs. It also included countless hours of power tool usage as I finished up interior trim, doors, along with some shelving and storage projects after we moved in. Record low temps during a Polar Vortex event in late January and into early February added to the total as well.

For 2020, a substantial increase in overall energy use might have been the expectation after the outbreak of COVID-19. Yet even after subsequent stay-at-home guidelines that began for us in March, we actually ended up at 10,446 kWh, a slightly lower annual number compared to the previous year. This lower total happened even with all three of us being home most of the time, with no breaks even for vacation time, outdoor activities that require some travel, or normal visits to family out of town.

If there’s a payoff in pursuing Passive House, it has to be in the combination of lower energy costs and increased occupant comfort when compared to a similar, conventionally built home or structure.

This lower number was in keeping with our usage during our first nine months (April-December, 2018). If the Polar Vortex was an anomaly (everyone hopes that it was), then most years going forward should be around 9,500-10,500 kWh for total annual demand. In part we think going over 11,000 kWH our first full year reflects just how significant a colder than normal winter can be on overall energy use in a Passive House, not to mention heating demand more generally (whether it’s a Passive House or not).

Moreover, for a family of three and a structure of this size with similar performance specs, it seems to suggest that our 3-4,000 kWh of annual usage per person is mostly ‘baked-in’. Meaning, in terms of occupant behavior, there’s not much we could do to further lower these numbers. Perhaps we could take fewer showers, cook less at home (stove and dishwasher), do less laundry, only ‘live’ from dawn to dusk (to avoid using artificial lighting at night), not do any woodworking or other DIY projects (use power tools off site?), and heat the home to only 60º F in the winter and cool to only 85º F in the summer. Obviously, these would be rather extreme measures to chase after the last final few kWh of energy use and, arguably, it wouldn’t be particularly meaningful apart from bragging rights should we end up with a lower annual total.

After all, it’s fair to ask what’s the point of the air sealing, insulation, and triple pane Passive House windows and doors, if it doesn’t produce a much more comfortable day-to-day living experience for those living inside the home or building? If simply chasing energy use were the main objective, reducing it no matter the consequences, then removing all the windows and doors and replacing them with continuous R-40 walls would be a good place to start, but hardly worth considering for obvious reasons. If there’s a payoff in pursuing Passive House, it has to be in the combination of lower energy costs and increased occupant comfort when compared to a similar, conventionally built home or structure.

In terms of unexpected surprises, really the only unanticipated energy use was the need for dehumidification on the hottest and most humid summer days of the year.

After our first summer in 2018, when part of the excess humidity was likely due to new construction moisture present inside the structure, we’ve been averaging about 30-40 days a summer, including a few random days in spring and fall, when the dehumidifiers are running intermittently. We set the units to 50% relative humidity, but normally they shut off around 55% based on gauges placed around the house. We try to keep the house under 60% RH. The risk for mold increases above 60%, but it’s mainly at that point when humidity levels make us feel noticeably uncomfortable.

Also, we didn’t think about the energy use associated with power tools for woodworking and arts and crafts projects. Without tracking it, we can only guess that it represents a few hundred kWh a year, rather than something in the thousands. We’ve been doing plenty of projects around the house our first three years, but still far less than what a full-time woodworking company would require. Even so, along with the potential for a EV charger, it’s something to think about when designing a new home or retrofitting an older one, especially if renewables are part of the equation and you’re trying to establish likely annual demand.

Actual Energy Use: Demand and Costs

The breakdown is as follows:

Based on our first 2.5 years in the house, we can expect 10-11,000 kWh of total energy use per year. Again, for some context, this is for a family of three, in a 1,500 square foot single story home that has a full basement.

In our first full year, 2019, we exceeded 11,000 kWh mainly due to the Polar Vortex. Compared to our first winter, along with numbers for this current season, it looks like the Polar Vortex added nearly 1,000 kWh of demand above a more typical January – March time period.

Over the course of our first 2.5 years (our first year was April-December), the numbers have been surprisingly consistent across seasons and month-to-month, regardless of our level of activity in the home (e.g. guests staying over, vacations away from the home, power tool use, etc.).

For instance, even in our first June, back in 2018, when the house was still drying out from new construction related moisture, and we felt compelled to start using two dehumidifiers to control excessive humidity (one in the kitchen and one in the basement), total energy use for the month was 616 kWh.

The following June, in 2019, we ended up with an even higher number, at 786 kWh of demand.

For June of this year, even with stay-at-home restrictions for COVID-19 in place, so a reasonable expectation might be for still yet higher demand, we actually ended up at a lower 605 kWh of use.

On a side note, it’s probably reasonable to assume COVID-19 had some impact on overall energy use for 2020, but after going through the numbers, it just seems unlikely that it contributed more than 500-1,000 kWh to our annual usage. We should have a better idea of its full impact once winter is over.

Presumably, without a granular study of day-to-day conditions, including day and night temperatures, along with relative humidity data, not to mention minor fluctuations in how we used the AC or how much laundry we were doing over these same three periods, it’s hard to explain this deviation with any level of certainty. Suffice it to say, we can expect June usage to normally be in the 600-800 kWh range. Obviously, a June in the future that experiences a heat wave like the one Chicago experienced in 1995 would likely drive the final number well over 800 kWh, but hopefully that remains a singular event rather than a more normal June.

In other words, even in a year where the weather remains milder than normal for a full 12 months, and we’re all exceedingly busy and rarely at home, our total energy use for the year, at best, will likely still end up in the 9,000-10,000 kWh range. And even if there was just one person living here, it’s hard to imagine they could keep total energy usage much below 4-5,000 kWh on an annual basis since so much of the demand is ‘baked-in’, as previously noted above.

Here is the monthly breakdown of energy use for the first full year we were in the home for 2019:

January: 1,738 kWh (includes 2019 Polar Vortex; following January was only 1,374 kWh)

February: 1483 kWh (the following year was 1,237 kWh)

March: 837 kWh (following year was 561 kWh — clearly a bitterly cold winter)

April: 681 kWh

May: 473 kWh

June: 786 kWh

July: 612 kWh

August: 608 kWh

September: 630 kWh

October: 812 kWh

November: 1,166 kWh

December: 1,237 kWh

Total energy use for 2019 was 11,063 kWh.

In this same period, our solar panels produced 3,863 kWh, so net demand for the year was 7,200 kWh (this requires some math using the billing statements from our utility company and the Enphase Enlighten solar app).

Our monthly bills for electricity in 2019 totaled: $1,075.89.

Because of our SRECs, which for us totaled $848 for the year (paid via quarterly checks), our net energy costs for 2019 were $227.89 (an average of $18.99 per month).

For comparison, numbers for 2020 were: 10,446 kWh of demand, while solar production for the same time period was 3,675 kWh, for a net energy demand of 6,771 kWh.

After SREC payments (again, totaling $848 for the year), our net total cost for 2020 was $189.36 (an average of $15.78 per month).

The SREC payments (these are based on a 5 year contract) reduced our annual cost by $848 each year, with a net average cost for our first two years of just $208.63 per year for all of our energy needs (a roughly $17.39 per month average).

Without any solar panels or SRECs, our electric bill would be roughly just under $1,500 per year based on current rates. By way of comparison, a new code-built home of the same size would likely pay more than twice this amount — an older home still more, assuming less air tightness and insulation, combined with a less efficient gas furnace for HVAC and domestic hot water.

It’s worth noting that as building codes tighten up their performance metrics, the difference in total energy demand between code-built and Passive House homes should continue to shrink. This assumes, however, that any number of ‘ifs’ are successfully overcome. For example, if air leakage is accurately measured (is there enforcement should the structure fail?). If a proper Manual J has been completed. If HVAC ducts are sized, installed, air sealed, and insulated properly. If insulation has been properly installed in appropriate quantities throughout the exterior walls and roof. If thermal bridges are avoided. If moisture (bulk and water vapor) is appropriately addressed and managed. This is a lot to get right, and it’s easy to get any number of things wrong, even with inspections and third party verification.

As pointed out earlier, since we’ve moved in we haven’t aggressively pursued trying to lower our energy demand. Instead, our approach has been to live ‘normally’, enjoying the benefits of the air sealing, insulation, and our HVAC set-up. We set and mostly forget our heat pump at 70º F in winter, 75º F in summer, in order to try and better understand ‘real world’ energy demand in a tight, well insulated and appropriately ventilated home of our size.

Hopefully some of this information can benefit others in the planning stages of their own Passive House, or Pretty Good House project. Moreover, in addition to WUFI analysis and PHPP, BEopt is another modeling option for figuring out energy demand and cost-effective design elements for a structure (new or old). The new calculator from PHIUS would also be a good place to start: PHIUS+ 2021

For anyone who wants an easy, initial test of their current home’s energy efficiency (EUI), a calculator like this one may be helpful: Energy Smart

Numbers for Heating and Cooling

In spring and fall when there’s less demand for heating or AC, our baseline monthly energy usage is below 500 kWh (this has been fairly consistent over the course of our 2.5 years in the home, even during COVID-19 when the three of us were home most of the time).

If this low demand could be maintained for much of the year, as it is in milder regions of the country like in parts of California, our annual usage could be cut by more than half (it wouldn’t require R-40 walls or R-80 attics to achieve either). Moreover, in these more temperate regions of the country with reduced insulation needs, and therefore less demand on HVAC systems, ‘green’ building programs like Passive House and Net Zero become even more attractive since they’re far more cost effective and easier to achieve.

In our case, summer months typically run about 600-800 kWh of actual usage, dependent on the number of days above 82º F when we typically find that we need to turn on the AC. Even on these days we will turn it off if there’s a sufficient drop in outdoor temps overnight, which allows us to open the windows (dependent on outdoor humidity or rain).

It might be worth noting that even though we thought we’d regularly open our windows whenever the weather was remotely nice, this hasn’t turned out to be the case. Between having to monitor indoor humidity levels, and the ability of our ERV to deliver continuous filtered fresh air (it’s shocking how quickly our fresh air supply filter turns black — within a month or two at the most), apart from the few days a year when the weather is perfect for opening windows, they mostly just stay shut. Much like Jim Gaffigan’s quip on seasons here in the Midwest, “Spring, that’s a fun day,” because the weather tends to be so mercurial there just aren’t that many days or nights when we feel comfortable leaving the windows open for extended periods of time.

On the plus side, it’s not uncommon for us to wait until there are 2-3 successive days where temperatures rise above 82º F before we feel the need to turn on the AC. In other words, there is some truth to the idea that Passive House buildings take some time to heat up or cool down based on outdoor conditions, although this can be quickly undermined by an ERV/HRV that’s set on high or in boost mode for long periods of the day (lots of cooking or showering, particularly relevant in the case of larger families, would make this a necessity) .

“Heating and cooling energy – that which is most reflective of the efforts of the design and construction process – is a small percentage of the total energy usage. As Andy Shapiro says, there is no such thing as a net zero house, only net zero families. Occupant choice matters hugely.”

—Marc Rosenbaum‘s report on South Mountain Company’s Eliakim Net Zero Energy Project

During the heart of winter, our total energy demand is in the range of 1,000-1,500 kWh per month. Even in January of 2019, with a Polar Vortex event, our bill still managed to stay below 2,000 kWh for the month. During this same week, however, we saw minimal benefit from our solar panels since they were covered by several inches of snow during the sunniest (and coldest) parts of the billing period.

These elevated kWh numbers during winter reflect just how much harder our Mitsubishi heat pump system has to work in order to maintain indoor comfort because of the Delta T between outdoor and indoor temperatures. And we can hear the difference: while in summer the system is virtually silent, in winter, especially as temps head towards zero, we can hear the compressor outdoors working to keep up. Compare this to summers: 75º F indoors vs. 95-100º F outside on the hottest days of the year, even though it’s significantly cooler for most of the summer, thus helping to explain the lower overall energy demand for AC usage in comparison to heating demand.

Cooling, unlike the demand for heating, is relatively comparable to what it would be in a conventional new build. In summer, the Passive House ‘thermos-like’ structure is mostly a hindrance rather than a benefit to keeping the interior comfortable. All the ‘free’ sources of heat in winter, e.g. south-facing windows on sunny days, body heat from the occupants, heat given off by computers, TVs, appliances, and even LED lights or our heat pump dryer, either thankfully don’t exist (in the case of south-facing glass because of sufficient overhangs) or they actively contribute (however small in some cases) to the overall cooling load.

In addition, because cooling loads are relatively low, and the efficiency of the mini-split heat pump is so high, even as the multiple indoor heads have no issue maintaining comfortable temperatures (we rarely notice the system — wall units or outdoor compressor — running in summer), it leaves us with a latent load that we need to address with two stand-alone dehumidifiers, indirectly adding to the overall cooling load.

So of our roughly 10-11,000 kWh per year of total demand, without an actual energy use monitor like TED on our main panel to establish exact numbers (a review of similar product options: here), it looks like just over 3,000 kWh is used for heating, with another 800-1,000 kWh used for cooling needs (at least in a typical year). In years where there’s a significant Polar Vortex event, or should a summer in the future experience an extended heat wave, then our numbers for heating and cooling are likely to hit 5-6,000 kWh of demand. With climate change, these numbers are invariably going to fluctuate or even grow depending on just how severe weather patterns become over the ensuing years and even decades.

Notes on Designing a Heat Pump System for Passive House

An issue worth considering, especially for those in the design stages of a build, is the added efficiency of a 1:1 set-up for heat pumps, meaning one outdoor compressor for each distribution head indoors (or air handler). There appears to be a growing consensus that this layout will offer added efficiency because of improved modulation over what has been a more typical set-up, like ours, which is a multi-zone system that has multiple distribution heads on a single compressor. It’s hard to imagine, at least in our case, that this impact could be more than a few hundred kWh per year, but worth exploring when having someone do a Manual J and S.

Additionally, we haven’t experienced any issues with the distribution heads in the two bedrooms (9k & 6k Btu’s respectively), either for heating or cooling, although concerns about the effectiveness of these undersized units in smaller bedrooms often comes up in discussions on how best to design and layout a heat pump system on Green Building Advisor.

When designing our system, I don’t remember this issue of 1:1 vs. multi-zone heat pump set-ups being discussed in any of the information I was able to hunt down, either in Passive House related books, or even online resources. I also didn’t come across discussion of the need for active, separate dehumidification while designing our build in 2016. These are just two examples demonstrating that Passive House is still actively evolving as a ‘green’ building program (potential overheating in winter and shoulder seasons would be a third example).

A cautionary tale for designers, as well as building owners, to guard against hubris as the construction drawings develop or when the details are finally executed on a construction job site. Other issues may arise with Passive House builds in the coming years, so it’s worth considering potential unintended consequences before finalizing details. Today’s solution may be someone’s costly headache tomorrow.

Additional Solar Panels to Achieve Net Zero?

Based on what we’ve been paying for energy in these first 2.5 years, we don’t feel compelled to add more solar panels at this time. Should the SREC’s dramatically fall in value with a new contract, or disappear altogether, it might encourage us, at that point, to purchase more panels for the roof. But even so, at less than $90 per month, even without the SREC’s, it makes our energy bills a relatively painless expenditure (roughly equivalent to one nice restaurant dinner for the three of us, or still less than what we pay on a monthly basis for things like coffee, breakfast cereals, and milk). Put another way, averaging around 3,500 kWh per person of demand, whether with or without the solar panels and our SRECs payments, our monthly energy bill is typically cheaper than a single visit to the grocery store.

Because of the effort and money expended upfront for air sealing and insulation, all while trying to carefully manage window placement and HVAC layout successfully, we’ve managed to whittle our energy costs down to something highly affordable and resistant to significant cost increases. This should remain true, regardless of what’s happening in the market in terms of prices for natural gas, coal, or nuclear power (i.e. the major sources of power in our region, here in the Midwest). Worst case scenario, we add additional solar panels to get to Net Zero or even Net Positive in order to cancel out what remains of our monthly energy bill. This would require an additional 7-8,000 kWh of annual solar production, or roughly three times what our current system produces.

In our specific case as a household — averaging between 3,500-4,000 kWh of solar production per year (this amounts to nearly 40% of our annual demand), combined with SRECs — we nearly end up at Net Zero, at least in terms of total cash spent for energy (arguably the most important — maybe the only — metric that homeowners ultimately care about; whether it’s the total cost to build a new home, or in terms of the annual energy bill). As a result, there’s not much financial incentive to purchase additional solar panels to achieve absolute zero energy consumption (this is in site energy terms only). The fact that this all comes with a house that’s extremely comfortable and quiet to live in, regardless of season or room, makes our home only that much more valuable to us.

Passive House + Net Zero?

In addition to designing for Passive House, there is the question of Net Zero or even Net Positive buildings. While Passive House strategies eliminate a significant portion of overall demand by requiring a significant outlay of upfront funds for air sealing and insulation, once this pill has been swallowed, it’s normally cost-effective to incorporate renewable energy of some kind to cancel out the expense of the remaining energy bill.

A quick side note: An excellent resource, one that I found only as our build was coming to an end, is William Maclay’s book The New Net Zero. It contains a wealth of information, but, in particular, many specific construction details vividly illustrated. This is especially valuable for DIY builders, or even seasoned professionals, when evaluating all the possible elements of roof-wall-foundation assemblies.

Also worth noting, if this approach (Passive House + Net Zero) were adopted on a national level, including renovations, it would eliminate a large portion of aggregate energy demand, thus having a meaningful impact on greenhouse gas emissions and global climate change (up to 40% for construction and existing buildings).

Based on what we know at the moment, a combination of approaches — including Passive House building principles, Zero Carbon goals, and the use of renewables — could be the way out of the climate crisis over the long haul. In addition, if adopted as part of building codes, it could mean properly training the next generation of tradespeople (like European-style apprenticeship models, thereby also improving the build quality) while also being a tremendously effective jobs program.

Beyond Net Zero, or even Net Positive, in regards to energy demand, there is increasing awareness about carbon emissions more generally, and the variety of ways to radically reduce or sequester it, including the choice of building materials (for new construction or retrofit projects) or even how we decide to landscape our yards.

Passive House Cost Premium

Unfortunately, due to relatively inexpensive utility rates here in the Midwest, even though Passive House (or Pretty Good House) offers a significant reduction in energy costs if done well, when considered as a percentage of household income the numbers may appear much less impactful or motivating when faced with line items in a build budget for things like air sealing and levels of insulation that far exceed building code requirements.

In our case, the annual energy savings compared to something code-built would likely be in the $2-3,000 range. Fairly significant, but if the purchase price of the home is $500,000 – 1,000,000+ (fairly typical here in the Chicago suburbs for new construction) then even a $100,000 savings over the course of a 30 year mortgage may not convince someone to move beyond conventional construction practices (particularly if they have their heart set on a long list of high-end finishes and appliances). The upfront costs associated with meticulous air sealing and added levels of insulation — if not viewed as an investment in build quality — will likely appear frivolous to the average consumer.

“One of the issues we face here is the fact that energy is cheap, like most things in the Midwest. We don’t have the financial burden placed on us that the coasts do—real estate-wise and energy-wise. So there is not much enthusiasm around green building on a financial level; it’s almost always an ethical issue. The people who are interested want to do a good thing for the environment, as opposed to saving money on their utility bills. Another thing is that people are accustomed to discomfort—we have drastic and frequent temperature swings. It’s really humid in the summer and freezing in the winters, when drafty windows are just accepted. They are used [to] it, so it is hard to sell them on high-performance windows to be more comfortable; or taking measures to keep a basement from being wet—they just aren’t concerned about it. There’s a complacency that we fight against; there’s not enough financial gain to incentivize making upgrades.” — Travis Brungardt, GBA Q&A

Looking solely at upfront costs is likely to discourage most prospective homebuyers from pursuing Passive House (or even Pretty Good House in many cases), whereas looking at the cost of ownership, including the cost of monthly utilities, produces a more accurate comparison (note, however, this assumes the homeowner can stay put for at least the next twenty to thirty years).

A cost of ownership calculation should also acknowledge less maintenance costs year-to-year since, if the structure is detailed well, it should experience far fewer issues (none ideally), especially damage caused by bulk water intrusion, mold, or even air leakage. Granted, it may take a decade or more before this kind of damage is found in a conventional home, but when it is, it’s rarely (if ever) inexpensive to properly correct.

Hard Choices

As a culture, we have been in a similar place before. One quick example would be automotive engineering applied to car safety. In terms of perspective, if you get the balance between cost and safety wrong when evaluating value, then seat belts, air bags, and better designed bumpers might seem like misspent dollars.

“Nader argued that Detroit willfully neglected advances in auto safety, like roll bars and seat belts, to keep costs down… But using [seatbelts] was strictly voluntary. And many Americans didn’t want to.”

— Daniel Ackerman, Before Facemasks, Americans Went to War over Seat Belts

In a similar vein, the American consumer has been taught by the market, realtors, and builders to believe cost per square foot is the gold standard of value. As a consequence, little emphasis is placed on building science basics such as air tightness, proper moisture management, thermal performance, or indoor air quality. In layman’s terms, this means the average American home is leaky, parts of it have likely been damaged by bulk water or mold, and it’s uncomfortable in terms of indoor temperatures and humidity, all while delivering subpar air quality to its occupants.

In terms of quality construction and ‘green’ building (Passive House or not), the hard truth is there really is no free lunch (not even renting: rentcafe). Quality, of any kind — finishes, proper moisture management, occupant comfort, even reduced energy bills — has its price, but only those who recognize its value will be willing to pay for it.

Regardless, as homeowners we either pay upfront for the air sealing and insulation, along with high performance HVAC for better IAQ, or we pay monthly (and perpetually) in the form of higher energy bills (this normally comes with less occupant comfort) and far inferior IAQ. Either way, the money is going to be spent, it’s just a question of when (upfront vs. long term month-to-month) and for what (air sealing and insulation vs. mediocre systems and underwhelming outcomes that require costly maintenance over time).

As with car safety in the past, depending on one’s point of view, the answer to these kinds of construction and homeownership options are either obvious or nonsensical. Nevertheless, regardless of the path taken — conventional construction or some version of high performance — no one’s wallet will remain closed for long.

Passive Solar: The Beauty of Light

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Does Passive Solar Design Still Make Sense?

Our ‘green’ building adventure began in 2013 when I came across various Passive House and high performance projects in Prefabulous + Almost Off the Grid by Sheri Koones. The red house featured on the cover and built by GO Logic, in particular, seemed like a striking departure from conventional homebuilding as practiced in the US.

In its overall shape it echoed an earlier project that I only became aware of later, the Smith House in Illinois by Katrin Klingenberg.

Arguably, in both cases, these homes have too much glass on their south elevations, both in terms of potential overheating of the interior and in purely aesthetic visual terms. Nevertheless, using south-facing glazing to bring in the sun during the winter months while getting some Btu’s of free heat made a lot of sense to us, especially in a heating dominated climate like ours here in the Chicago area.

By the time construction began, we had settled on what seemed like a significant amount of windows and a kitchen door for our south elevation. We felt the layout would be an appropriate amount both in terms of passive solar heating and aesthetics, in addition to daylighting needs.

Moreover, by addressing the main weaknesses of the original Passive Solar movement of the 1970’s, namely the lack of air tightness and sufficient levels of insulation, we hoped that we could strike a balance between enjoying the seasonal movement of the sun in and out of our home while mostly eliminating the risk of overheating, even during shoulder seasons (spring and fall).

Since our build, however, there appears to be growing concern about just how effective this design strategy really is for Passive Houses or high-performance homes more generally. In effect, are the potential savings on a heating bill really worth the risk of temporarily overheating interior spaces?

Joe Lstiburek, of Building Science Corporation fame, puts it bluntly when quoted in a GBA article regarding the use of high SHGC glass:

“Don’t bother with the passive solar. Your house will overheat in the winter. Yes, you heard that right. Even in Chicago. … You should go with very, very low SHGCs, around 0.2, in your glazing. If this sounds familiar to those of you who are as old as me, it should.

“We were here in the late 1970s when ‘mass and glass’ took on ‘superinsulated.’ Superinsulated won,” Lstiburek continued. “And superinsulated won with lousy windows compared to what we have today. What are you folks thinking? Today’s ‘ultra-efficient’ crushes the old ‘superinsulated,’ and you want to collect solar energy? Leave that to the PV.”

Clearly, he’s not entirely wrong, especially when some of the early failures in the Passive House movement revolved around this very issue of overheating. If you were an early adopter of the Passive House concept, especially if you were the homeowner, and you ended up with comfort issues because of too much glass on your southern facade it certainly would make you doubt the purported precision of the Passive House energy modeling.

Nevertheless, with careful planning, it is possible to avoid this issue of overheating while still getting to enjoy most of the benefits associated with passive solar design. In our case, this meant limiting windows on the north side (net energy losers) to just our daughter’s bedroom, while glazing on the east side shows up only in a small area of our front door.

Small amount of glass in our front door offering some daylighting benefit for our entry area.

In addition, we avoided any potential for overheating from our west-facing windows by using self-tinting Suntuitive glass in our master bedroom and family room. This glass can fluctuate in its SHGC between (.08 – .18) depending on whether in its fully tinted or clear state (varies depending on surface temperature of the glass).

West facade with self-tinting Suntuitive glass.

With the other three sides of the house accounted for, we were able to concentrate all of our attention on the best window layout for the south side of the house. The utility room, which is on the southeast corner of the house, only really needed a small window, so we went with a single 3′ x 5′ unit. In the kitchen, the window above the sink was already going to be limited because of the lower cabinets, and was mainly for a view while doing dishes. This unit ended up being 4′ x 5′. For the kitchen door we went with a mostly glazed door with privacy glass, which has worked out well as it lets in an abundant amount of daylight while it’s never caused any issues with overheating.

The real challenge was getting the family room window on the south side of the house sized correctly. The temptation was to go too large since we had the space to do it. Instead, we wanted to retain some empty wall space for artwork on either side of this window, while also remembering that even the best window is still a lousy wall (e.g. R-40 wall vs. R-6 window).

In the end, we decided to go with a 3′ x 9′ window in our family room, slightly smaller* than the units on the west facade with Suntuitive.

{*7-27-20 Correction: I messed this up. The dimensions weren’t different between the south-facing family room window and the west-facing windows with Suntuitive — it was a height off the floor change. For the south-facing family room window we went slightly higher, 32″ off the finished floor, in order to gain a little more privacy, while on the west-facing windows we maintained a lower height of 27″ off the finished floor to maximize our views out and into our backyard. This 5″ difference may not sound like much, but it has a dramatic effect in terms of overall views and perspective when standing at these windows.}

In terms of wall area on our south facade, the windows and kitchen door account for just under 15% of the total, so not a crazy amount, and obviously nowhere near the amount of glass in a curtain wall.

The Sun’s Path Month-to-Month

For those who haven’t directly experienced a space that utilizes passive solar design principles, it may be helpful to see in photos what exactly this effect means month-to-month in a real home.

In our case, we have a long interior wall that runs east-west along the longest axis of our home. This wall effectively separates the private areas to the north (bedrooms and bathrooms) from the public areas to the south (family room, kitchen, and utility room). For context, this long wall stands almost 16 feet from all of the south-facing windows.

In our kitchen and family room, here’s what the sun looks like near midday in January:

jan fmly rm
Sun in January, slowly moving away from the back wall (at right) that runs east-west along the longest axis of the house.
jan ldry rm
Sun pouring into the utility room in January.

By the middle of February, the sun is already making its way towards the windows, barely able to reach the family room couch, while it still adds plenty of sunshine and warmth to the kitchen and family room areas:

sun feb fam
Sun in mid-February.

By the Spring equinox, the sun has continued its slow march across the family room floor towards the south-facing windows:

sun mar fam
Sun in March.

In the basement, with the help of two large south-facing windows (each 4′ x 4′) and our oversized window wells, the sun is making the same progression as it brightens up the below grade space:

sun mar base
Basement in mid-March.

Although we chose to forego any windows on the east side of our house, mainly for privacy and energy loss reasons, the small amount of glass in our front door still allows our entry area to be bathed in beautiful early morning light without contributing a significant amount of heat gain:

sun mar morning east
East-facing entry area flooded with morning light from the minimal glazing in the front door.

The seasonal path of the sun can also be marked on the exterior by its progress up or down the facade of our south elevation. By mid-March you can see the shadow line formed by our substantial roof overhang beginning to make its way down the siding — at this point, just above the windows and kitchen door. This invisible ‘curtain’ will cover the glass in the windows entirely by the end of June, completely denying the heat of the sun direct entry into the structure.

sun ext mar
South elevation in mid-March. Note the shadow line just above the windows and kitchen door.

Even in April the sun is mostly denied entry; reduced to a sliver of light hitting the wood floor in the family room:

sun apr fam
Family room in April.

In June, by the time of the summer solstice, the sun has been pushed outside completely, limited to the metal sill pans on the exterior of the windows.

Our south elevation during the rough framing stage. Layout from left to right: family room, kitchen door, kitchen window, and utility room.

With significant and thoughtfully placed windows on the south side (combined with a substantial roof overhang), we’re able to enjoy views to the outdoors year-round, allowing us to maintain an unbroken connection to nature in our yard, without any of the heat or glare normally associated with the summer sun. It also means we don’t need to bother with curtains or other window treatments, or the hassle of managing when they should be opened or closed.

Also, since the transition from winter (welcoming the sun in) to summer (denying the sun entry) has proven to be seamless, we’ve been able to avoid installing any curtains or window treatments in order to hide from any periods of unwanted sunlight. Basically, this invisible ‘curtain’ effect of passive solar design means we enjoy all the benefits of window treatments without any of the hassles (routine opening and closing, cleaning, or maintenance and repair), all while maintaining an unobstructed view of the outdoors. This is especially rewarding during the long winter months when starved for sunlight and extra warmth, but equally pleasurable as life begins to hum in the yard with the return of spring and summer.

In the photo below, the family room window (at left) and the kitchen door are protected from the heat of the sun by the roof overhang. The window on the back wall (facing west) is protected by self-tinting Suntuitive glass, which also allows us to enjoy unimpeded views of our backyard without the need for curtains or window treatments, even on the sunniest and hottest days of summer.

sun june fam
Family room in June with no direct sun allowed entry into the space.

On the exterior, by the middle of June, this shadow ‘curtain’ has fallen over the entire face of the south-facing windows, denying the sun entry into the home where it could cause unpleasant glare and unwanted heat gain (these windows have a SHGC of .54), which would needlessly increase cooling loads for our Mitsubishi heat pump system, while also reducing overall occupant comfort.

Around the summer solstice in June, this is what the set-up looks like outdoors:

Southwest corner of the house around the summer solstice.
A second view of this ‘curtain’ effect; this time from the southeast corner of the home.

This effect is also visible from the interior while looking out the south-facing windows. With a substantial roof overhang the sun can barely reach the metal sill pans by the middle of June:

sun june util
Utility room window in the middle of June. Note the sun hitting the outside edge of the metal sill pan.

In June, the sun is able to get slightly deeper inside the home in the basement — in this case managing to hit the surface of the window stool or sill.

sun base june

Even in the heart of the summer, the sun is still denied direct access to the interior spaces on the main floor:

sun july fam
Family room in July. The sun remains outside.

A second look at the metal sill pan from the utility room window, this time in July:

sun july util

After slowly making its way back into the south-facing living areas, by November the sun is once again approaching the back wall in the family room and kitchen:

sun nov family
Family room by mid-November.

Even though the utility room window is a relatively modest size (3′ x 5′), it provides ample daylight and plenty of warm sunshine over the course of our long winter months:

sun utility nov
Sunlight spilling out of the utility room by mid-November.

Here’s another view of the sun exiting the utility room on its way to the back wall in the main living area:

sun utility nov 2
Sun in mid-November.
sun nov kitch
Sun hitting the kitchen countertops in November, bathing the space in a warm glow.

By late December, around the winter solstice, the sun is finally able to hit the back wall in the main living area, maximizing the amount of direct sunlight that enters the house:

sun dec family mbr
Sun during the winter solstice, at the doorway to the master bedroom.

sun kit dec
In late December, the sun hits the back wall where the family room meets the kitchen.

sun dec utility barn door
Sunlight from the utility room window hitting the barn door in the main living area.

Even in the basement, where it’s more difficult for the sun to make its way into the space, with our oversized window wells and two large windows the sun manages to get very close to the center of the space just in front of the structural beam. This light pouring in helps keep us connected to the outdoors, mostly eliminating the cave-like feel normally associated with many below grade spaces. Even on the coldest days in winter, this daylighting effect makes the basement a warm, inviting space.

basement bfws sun
Sunlight entering the basement in mid-December.

Some Final Thoughts

We were expecting to enjoy the seasonal movement of the sun, watching it progress in and out of the main living space, warming us in the winter while also helping to moderate summertime AC demand. One unanticipated surprise, however, is how effective our window layout has been in maintaining a high level of daylighting, even on the grayest of overcast days.

Short of a menacing thunderstorm that turns the skies gray-black, we almost never have to turn on lights during the day. For instance, in the photo below it has snowed overnight, and the skies are an unrelenting blanket of gray. Nevertheless, because daylight has ample means for entering the living space, no artificial light is necessary. Note, too, in the background, how clear the Suntuitive glass is when not in its fully tinted state.

The kitchen door, because it consists mostly of privacy glass, contributes a great deal to this daylighting effect — both in summer and winter — and we’re extremely happy we didn’t choose a more opaque door style.

Another side benefit in this regard is how the porch light outside this glass-filled door also acts as a de facto night light for the kitchen — its soft, but effective, glow makes it easy to navigate around the space in the middle of the night without having to turn on any interior lights.

cloudy day still light
Even on a cold, gray winter day the windows allow in a great deal of daylight, dramatically improving the overall livability of the space while allowing us to keep the lights turned off.

One final, unanticipated surprise is how much the house is flooded with light on cloudless nights when there’s a full moon. The moonlight creates a soft, beautiful source of light as it falls across these interior spaces.

In terms of shoulder seasons, when sunlight still has some access to the interior but outdoor temperatures are mild or even occasionally warm, we haven’t really noticed a problem. In spring, if outdoor temps should reach the 70’s during the day it is frankly welcomed with open arms, as we’re starved for warm sunshine at winter’s end. In the fall, if there’s an occasional too warm day, we simply open a couple of windows. So far we’ve never had to turn on the AC in October, for instance.

If there’s any failure in our set-up, it would be the family room couch. From the end of December until the end of January, if it’s a sunny day, regardless of how cold it gets outside, sitting on the couch is uncomfortable, if not impossible. Sitting in shorts and a tank top would be the only way to make it remotely comfortable.

Thankfully, we’re almost never on the couch during this time, so it’s never been a problem for us. Having said that, if this family room were dedicated office space and I needed to be sitting at my desk from 10am-2pm, it would be extremely uncomfortable. This is a good example of how carefully not just an overall floor plan needs to be designed, but how even individual spaces need special attention, in particular for year-round HVAC comfort based on how occupants are actually going to be using the space.

Overall, we’ve been very pleased with the layout of our windows and their ability, in conjunction with the roof overhang to the south, to allow in ample amounts of sunlight during the colder months while still being able to keep it out on the hottest days of the year. With detailed planning, our experience suggests that designing living spaces for a real passive solar benefit is still a worthwhile goal.

Although it may be safer to ignore this design strategy altogether in the hottest climates (simply designing to keep the sun outside year-round may be the better option, which would include the use of low SHGC glass as Lstiburek recommends), passive solar has proven to be a great source of enjoyment for us, particularly during our winters here in Chicago, which tend to release their grip too slowly and ever so begrudgingly.

If given the chance, we would definitely design our house again with these passive solar techniques in mind.

Completing our Wall Assembly: Rockwool Batts, Intello, and Drywall

4

Insulation for Exterior Walls

Once Wojtek and Mark were done installing our continuous insulation on the exterior side of our Zip sheathing (4″ of Rockwool Comfortboard 80), including the first layer of battens (no more errant fasteners through the Zip to worry about), I was able to move inside and begin installing Rockwool Batts (R-23) in our 2×6 wall framing.

Once we had moved on from our first builder, and after reading up on the available options for insulation, we decided to invest in Rockwool insulation, both the rigid Comfortboard 80 on the exterior of our sheathing and the Rockwool batts for inside our stud bays. Although more expensive, particularly the Comfortboard 80 for continuous insulation (used rigid foam would’ve been substantially less expensive), we felt that many of its properties made it worth the added cost.

In particular, by helping our wall assembly to be vapor-permeable (or vapor open), we felt the Rockwool could help mitigate any mistakes, should they be made, in the wall assembly details. This being our first build acting as a GC, we wanted to add some margin for error wherever we could find it.

More details on our wall assembly and how we finalized details, including our desire to maintain a high level of IAQ, can be found here: Wall Assembly

For environmental reasons, one of our goals was to try and be as “foam free” as possible throughout the build. In addition, beyond just this issue regarding the use of foam (in all its forms: rigid board and sprayed varieties alike), there’s increasing awareness about the carbon footprint of our structures, not to mention the total carbon footprint of our daily lives.

At any rate, if I had it to do over, I would at least seriously consider using reclaimed rigid foam for our continuous insulation over the sheathing (both for the potential cost savings and its status as a reclaimed material otherwise headed for a landfill), understanding that it does reduce a wall’s ability to dry to the exterior. As others have noted, using reclaimed rigid foam in this way may be the best, or “greenest”, use of foam insulation until the construction industry hopefully moves beyond its use altogether as better options become more viable (e.g. wood fiber insulation).

Here are some resources for reclaimed rigid foam:

http://insulationdepot.com/

https://www.reuseaction.com/sales/foam/

https://www.greeninsulationgroup.com/

https://www.repurposedmaterialsinc.com/polyiso-insulation/

I would also consider using dense pack cellulose in the 2×6 walls instead of the Rockwool batts if I could find an installer I was reasonably certain could do the work properly. During construction it felt safer to use my own labor to install the Rockwool batts, thus avoiding the possibility of any gaps in the wall insulation. I was hoping to offset the cost of the batts with my free labor, plus I just enjoyed doing the work. Had we gone with the dense pack cellulose, it would’ve been something I couldn’t do on my own (no equipment or training).

lights on in base 4 rockwool
Basement ready for Rockwool batt insulation.

Installing the Rockwool batts is fairly easy and satisfying work. They’re much easier to work with than fiberglass batts, which are horrible on your skin and tend to flop around as you try to get them into place. While the Rockwool also produces some irritating fibers when it’s cut (and requires a dust mask like fiberglass), I found that a shower easily washed them away. Wearing long sleeves during installation also easily mitigates this issue.

base knee wall w: rockwool going in
Insulating the exterior wall in what will be the basement stairwell.

Also, the fact that the Rockwool batts have a friction fit means they don’t require any additional staples or netting to get them to stay put once installed.

Because of the friction fit, it’s also easy to tear off small pieces to stuff into irregular shaped voids should the need arise.

rim joist w: and w:out rockwool
Basement rim joist without and with Rockwool batt insulation.

Like the Comfortboard 80, the batts can have some variation from one piece to another, with a change in the amount of density clearly visible. With the Comfortboard 80, this was significant enough that we avoided using the worst pieces, meaning those with the least amount of density (these pieces felt thinner and sometimes even crumbly). Although this inconsistency was still present in the batts, I managed to use almost every piece, saving the least dense pieces for use in some interior walls for sound attenuation (more on this topic below).

base kneel wall corner rockwool
Corner of basement with knee wall and rim joists insulated with Rockwool batts.

Overall, we were happy with the Rockwool batts, and would definitely use them again should dense pack cellulose not be a viable option. They’re also ideal for a self-build since anyone who’s reasonably handy can install them should they have the time available during construction.

rockwool around base beam
Rockwool batts packed into gaps around the basement steel beam.

In conjunction with the Intello that would eventually be installed over the 2×6 framing members and the Rockwool batts, we also used Flame Tech putty pads to air seal behind every outlet and light switch box. I had seen them used in a Matt Risinger video for sound attenuation:

The other option would’ve been to use airtight junction boxes. Here are a couple of examples: Small Planet Supply and 475HPBS.

In order to limit issues with all the air sealing I was doing, I tried to stick with products my subcontractors already used everyday. As a result, since my electrician wasn’t familiar with airtight junction boxes, I opted instead to come in after he had everything installed and apply the putty pads. I found installing them to be straightforward and pretty quick.

box label putty pads

The putty pads are attached to release paper. Once the paper was removed the pads were easy to mold around each outlet and light switch box.

label putty pad
Acoustical putty pads purchased on Amazon.

Here’s a completed outlet box:

putty pad on outlet
Putty pad molded around every outlet and light switch in exterior walls.

The trickiest area to detail for the walls was at the ceiling and wall junction. In our case, the roof trusses sit on 2-2×6’s turned on their sides, which sit on top of the wall’s double top plate. The 2-2×6’s create space for our service cavity under the bottom chord of the roof trusses.

extoseal-encors-as-gasket
2-2×6’s on edge, sitting on double top plates. Extoseal Encors acting as gasket once taped from the exterior face of the Zip sheathing over the top of the 2-2×6’s, thus completing an air sealed connection between the exterior (Zip sheathing) and the interior before roof trusses are set in place. More details here: Roof Details

Before cellulose could be blown into the attic, we installed Intello to the bottom chord of the roof trusses. At all outside edges the Intello was carried from the roof trusses down over the double top plates of the walls, anticipating the Intello eventually being installed on the walls, which required a connection point between the Intello on the ceiling and the Intello on the walls.

ceiling-wall b4 Intello - Rockwool
Ceiling and wall areas before installing Intello on the bottom chord of the roof trusses and Rockwool batts in the walls.

After the Intello was installed on the ceiling, a service cavity (or service core, or service chase) was created with 2×6’s screwed to the bottom chord of the trusses through the Intello.

string between junction boxes to make sure they're straight
Service cavity with 2×6’s attached to trusses through the Intello. More info on the service cavity here: Ceiling Details.

This gap was going to be a dedicated space for lighting and the 3″ Zehnder tubes of our ERV (as things turned out, we didn’t end up needing this space for the Zehnder tubes).

bare trusses - intello - intello w: single layer CB 80 - service chase
Intello coming down from the roof trusses to cover the double top plates on the wall.

Before installing the Rockwool batts in the walls, I was also able to fill this gap created by the two 2×6’s on their side that sit on top of the double top plates with leftover pieces of Comfortboard 80. The first piece of Rockwool fit snug inside the gap, while the second piece was attached to the first with some plastic cap nails and the friction supplied by the 2×6’s forming the service cavity. Some additional holding power was added at the gable ends by utilizing drywall clips (visible in the photo below):

intello onto top plates
Connecting Intello to top plates with a strip of Tescon Vana tape, creating a clean and solid surface for the eventual Intello on the walls.

The drywall clips were helpful in lending support to drywall anywhere that adding solid blocking would be time consuming or a physical challenge.

nailer for ceiling drywall
These drywall clips worked great in places where the sheetrock needed additional support.

Even though we utilized a 12″ raised heel roof truss, and we had 4″ of Rockwool on the exterior of our Zip sheathing, it was important to fill this gap created by the service cavity to make sure our thermal layer was unbroken around the perimeter of the house (4″ Rockwool on the exterior, 5 1/2″ Rockwool in the stud bays). The outside edge of the roof truss is also the most vulnerable to ice damming, so having the 4″ of Rockwool Comfortboard 80 directly below this area where blown-in cellulose would be installed offers some additional thermal performance to the attic insulation.

Another view of this area where roof truss meets the 2-2×6’s standing on their side, creating a gap between the bottom chord of the roof truss and the top plates on the wall below.

sealed top of wall from inside
Roof truss on 2-2×6’s turned on their sides, which have been sealed with Pro Clima tapes. HF sealant completes the airtight connection between the Zip sheathing and the 2-2×6’s.

If I had it to do over, I would go with a 24″ raised heel truss, as this would offer not only significantly more R-value in this area (for relatively little expense), it would also make any inspection or repairs in this area much easier to deal with.

mbr w: rockwool in walls
Installing Rockwool batts in the walls of the Master Bedroom.

As each piece of Rockwool batt was installed, it was important to keep any butt joints between cut pieces tight together. Also, once each piece was snug inside the stud bay I finished by gently fluffing the outside perimeter edges so the Rockwool sat as flush as possible to the 2×6 studs, thus maximizing their R-value.

mbr rockwool complete
Master Bedroom ready for Intello on the walls before drywall gets installed.
family rm w: rockwool
Family room ready for Intello and then drywall.

Intello

With 4″ of Rockwool Comfortboard 80 on the exterior of our sheathing, the code specifies that we could’ve just used latex paint as our interior vapor retarder (Class III).

Again, to improve our margin for error, I felt like it was worth the added expense and time to install a smart vapor retarder (CertainTeed’s Membrain product would’ve been another alternative) to avoid potential issues with diffusion in the winter.

When I asked a question on GBA about this issue, the consensus seemed to be that the Intello, although technically unnecessary, was a nice bit of insurance.

It also added a final layer to all of the previous air sealing details. With redundant layers of air sealing, even if small areas experience failure over time, there are still other areas to back it up, thus maintaining our overall air tightness for the long term.

intello at frt dr basement
Intello installed in the basement stairwell by the front door.
finishing intello mbr
Intello in Master Bedroom nearly complete.

Sealing the Intello to the subfloor was one of the final air sealing chores of the build. It was deeply gratifying to finally get to this point, especially since drywall and then flooring were up next.

tescon on intello at subfloor
Intello taped to the subfloor with Tescon Vana tape.
intello tvana complete mbr
Intello complete in the Master Bedroom.

Thoughts on Advanced Framing Techniques

If I had it to do over, I would use less framing around windows and doors, along with using pocket headers instead of the more traditional insulated headers we ended up with. Pushing the header to the exterior sheathing would mean being able to insulate the pocket on the interior side with Rockwool or dense pack cellulose, rather than the rigid foam we ended up with (unfortunately, XPS in our case).

family rm w: rockwool
Family room ready for Intello.

Before we had to fire them, the two GC’s we were still working with as framing began were unfamiliar with advanced framing techniques, and they were already struggling to comprehend the many Passive House details in the drawings (not to mention many of the conventional details) so, as I’ve noted elsewhere, I had to pick my battles carefully.

Another change I would make would be at points where interior walls meet up with exterior walls. Rather than using ladder blocking to make the connection, which is still better than more traditional methods (creating a boxed in void that’s virtually impossible to insulate), I would utilize a metal plate at the top of the walls to make a solid connection. In addition to making drywall installation easier since it would create space between the two intersecting walls for sheets of drywall to be passed through, it would also make installing insulation, especially batt insulation, much more straightforward with clear and easy access (no horizontal blocking to get in the way).

intello at ladder
Intello at partition wall that meets the exterior wall (using ladder blocking).

A ProTradeCraft article discusses what builder David Joyce believes is ‘worth doing’ in terms of advanced framing techniques. Perhaps just as important, he points out what he believes can be safely ignored, or is just ‘not worth doing’ when it comes to OVE.

In this Matt Risinger video, architect Steve Baczek delves into some of the key components he uses to optimize advanced framing techniques:

In addition to the pocket headers, the idea of using header hangers instead of additional jack studs, seems to make a lot of sense.

And here’s a ProTradeCraft video regarding their own take on Advanced Framing:

One final change to our framing would be opting for 2-stud corners instead of the California 3-stud corners that we have. Although a relatively small change, I think a 2-stud corner is cleaner and allows for slightly more insulation in this vulnerable area.

Clearly each designer, architect, GC, or framing crew will have their own particular views on advanced framing, so there’s room to make individual choices without undermining the goal of balancing structural integrity with reduced energy demand. Local codes, along with the opinion of your rough framing inspector, will also have to be accounted for.

My guess is these techniques will continue to evolve, especially if specific products come to market to aid the process (i.e. reduce the amount of framing lumber required while ideally also lowering labor costs, all without negatively affecting the overall strength of the structure).

intello kitchen
Intello in the kitchen complete.

One final attempt at some additional air sealing was around outlet and switch boxes as they met up with the Intello. With a bead of HF Sealant, it was easy to make an airtight connection between the Intello and the box.

cu intello at outlet
Completing connections around outlet and switch boxes with HF Sealant.

At doors and windows, I finished these areas off with a strip of Tescon Vana tape, just as I had at the top and bottom of the walls.

intello complete br2
Completing Intello around a bedroom window.

Because corners tend to be problematic in terms of air leakage, I also added a dab of HF Sealant to these areas for the sake of some added redundancy.

lwr lft corn wdw w: intello & tape
Lower left corner of window with some added HF Sealant in the corner.
upper rgt corner wdw w: intello
Upper right corner of a window just before final piece of Tescon Vana tape is run across the top of the window frame, tying together the Intello and the light blue Profil tape that is air sealing around the window.

Sound Attenuation

Since we designed our home with a smaller than average footprint, incorporating many Not So Big House principles (roughly 1500 square feet for the main floor, with another 1500 square feet in the full basement below), one way to make the floorplan feel larger than it actually is was to provide some sound attenuation in key areas (we incorporated several other techniques to “expand” the feel of the floorplan that will be discussed in upcoming posts regarding interior design).

For instance, we installed the Rockwool in the long partition wall that runs east-west down the center of the floorplan. This wall helps define the barrier between public areas (kitchen and family room) on the south side of the home and the private areas (bathrooms and bedrooms) on the north side of the home.

We could’ve used Rockwool Safe ‘n’ Sound, but at the time, during construction in the fall of 2017, it was a special order item in my area, whereas the batts were already in stock, both for my main 2×6 partition wall, a 2×6 plumbing wall, and the remaining 2×4 walls that we felt could benefit from the Rockwool.

In the photo below, the Rockwool in the main east-west partition wall is covering the refrigerant and drain line for one of our three Mitsubishi heat pump heads, along with the usual electrical conduit for outlets and light switches.

rockwool 2nd br entry hall
Rockwool added to some interior walls for sound absorption, thus reducing unwanted sound transmission between certain spaces.

Here’s another view of this partition wall, this time from the opposite side inside the second bedroom:

rockwool 2nd br interior side
Same section of east-west partition wall from inside the second bedroom.

We also added Rockwool to the wall that connects the master bath to the 2nd bedroom bath, and between the 2nd bath and 2nd bedroom. The Rockwool was even added to the wall between our kitchen and utility room, where we have our washer and dryer, in the hopes that it would limit the amount of noise coming from the machines (which it thankfully has).

rockwool bath walls
Rockwool in bathroom wall around main waste stack.

Although this doesn’t make for a totally sound proof connection between spaces (we weren’t prepared to take things that far — roughly equivalent to air sealing a Passive House in the amount of detail required), the ability of the Rockwool to significantly muffle sound between rooms is quite impressive and, for us at least, well worth the effort and added expense.

rockwool kitch - utility
Rockwool in the wall between the kitchen and utility room.

For instance, while standing in the master bathroom, should someone be running water or flushing the toilet in the 2nd bathroom directly on the other side of the wall, the majority of the sound that reaches your ear comes by way of the master bedroom doorway, not through the wall directly. Out of curiosity I tested this idea with music playing on a portable stereo in the 2nd bathroom with the same results — sound through the wall is dramatically muffled, while the same sound that easily travels out of the bathroom and makes it way via the bedroom doorway is crystal clear. With the door to the 2nd bathroom and our master bedroom door closed, this same sound is obviously further reduced.

It’s also nice to watch TV in the family room and know that as long as the volume is at a reasonable level you’re not disturbing anyone trying to sleep or read in the two bedrooms. This kind of sound attenuation also adds a level of privacy to the bathrooms while they’re in use.

And, again, it’s not that no sound is transmitted from one room to another, rather it’s almost entirely limited to doorways, thus significantly reducing the overall impact of the noise that is transmitted. In other words, our goal was rather modest, we were just after significant sound absorption, not sound proofing (e.g. the level of noise cancellation required in a professional recording studio or a high-end home theater room).

As a result, I would definitely use Rockwool for sound absorption again. In fact, I can’t imagine going without this kind of sound attenuation (or something akin to it using other products or techniques outlined in the videos above) now that we’ve been able to enjoy it in our new home. It effectively prevents the issues often associated with so-called “paper thin” walls.

Arguably, addressing this issue of unwanted sound transmission is even more important in Passive Houses or high-performance homes that are already much quieter than conventional homes because of the extensive air sealing and well above code levels of insulation. In our own case, outside noises either disappear entirely or are significantly muffled — this includes a commuter train a couple of blocks away.

As a result, any noises within the home itself become much more pronounced since they don’t have to compete with the typical noises coming from outside the home. For instance, when we first moved in the fridge in the kitchen was easily the most obvious, consistent sound in the house. After a couple of weeks it just became background noise we’ve grown to ignore, but it was surprising just how loud it was initially, especially our first few nights in the home when everything else was so quiet.

In addition to excessive air leakage and obvious temperature swings between rooms, along with poorly sized or placed window layouts, the lack of any sound attenuation between rooms is one of the issues we notice the most when we’re inside more conventionally built homes. Much like all of the conveniences associated with a modern kitchen, it’s easy to take something like effective sound attenuation for granted until you’re required to go without it (e.g. in the case of kitchens while on a camping trip or waiting for a kitchen to be remodeled).

With all of the Rockwool batts in place, and the Intello installed over the exterior walls, drywall could finally go up.

Drywall

We went with USG 5/8″ EcoSmart drywall (GBA article on EcoSmart). We chose the 5/8″ over 1/2″ mainly for added durability and some slight sound deadening between rooms.

I had read about Certainteed’s AirRenew drywall, but it sounded like the only VOC it absorbed was formaldehyde, which, if I understand the issue correctly, can be safely avoided with the use of appropriate cabinets and furniture. If memory serves, AirRenew works by utilizing a compound similar to triclosan, meaning a biocide, which some believe can have potentially serious health effects. It’s not clear to me, even now, whether the use of AirRenew drywall makes sense, or exactly what compound (or series of compounds) are utilized to absorb the formaldehyde since Certainteed has remained silent on this point, claiming the information is proprietary. Nevertheless, it has a Declare label, so ILFI must believe it’s reasonably safe to have on painted ceilings and walls.

At any rate, we wouldn’t be bringing in any new furniture that would have elevated levels of VOC’s (including flame retardants) once construction was complete. Since our last house was significantly larger, roughly 2,800 sq. ft., it was fairly easy to downsize, donating or giving away what we couldn’t use in our new house, while holding on to our favorite and most useful pieces. It also helped that we never really filled up our last house (e.g. we never got around to purchasing a formal dining room set), so we didn’t have as much “stuff” to discard as we might have.

Moreover, by being mindful of every finish we create or use (primers, paints, wood flooring, grout sealer, caulks and sealants, kitchen cabinets etc.), along with any other products we might bring into the new house (e.g. surface cleaners, new furniture, fabrics, even perfumes and colognes, etc.), we’re hoping to maintain a high level of IAQ.

The International Living Future Institutes’s Red List and their database of Declare products were a big help to us, even though we’re not pursuing any kind of certification with them. The Greenguard certified label was also helpful, in particular when it came time to choose tile and grout.

By consciously choosing every product and material that comes into the home, it’s possible to at least reduce our exposure to harmful VOC’s and chemicals. While still imperfect (Who can you trust?), these kinds of programs do allow designers and homeowners to take some control over the environments they’re creating and living in, which is empowering to a degree. Far better if the US regulatory bodies operated under a precautionary principle model when it came to industrial products.

Frankly, in a rational system, one that was truly looking out for the best interests of consumers, this kind of research — time consuming and frustrating busy work to put a finer point on it — would be considered laughable if not horrifying. In a rational system it would be safe to assume that any product for sale, apart from some careful instructions on their use and disposal, would be safe to have inside your home without having to worry about short or long term health implications.

Nevertheless, if unintended health consequences are to be avoided during a renovation or a new construction build, consumers have little choice but to do the necessary homework (or pay someone else to do it for them) and be as thoughtful as possible with their selection of materials.

drywall family rm
Kitchen and family room after drywall was installed. Ready for primer, paint, and flooring.

Now that all of the elements of our wall assembly were complete, it was time to have some fun with final finishes: flooring, wall colors, wood trim, doors, kitchen cabinets…

 

Siding Part 1: Continuous Insulation with a Rainscreen

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Continuous Insulation vs. Double-Stud Wall

Although builders can make either approach to high-performance walls work, we decided continuous insulation (or CI for short) made the most sense to us. And while continuous insulation has its own challenges, especially in terms of air and water sealing details around windows and doors, intuitively we felt insulation on the outside of our sheathing would give us our best chance at long-term durability for the structure.

In spite of the fact that these kind of wall assemblies are climate specific, for anyone interested in the performance of various wall assembly approaches this BSC paper is an excellent place to start:

High R-Walls

Or you can check out Hammer and Hand’s evolving wall assembly strategies here:

Passive House Lessons

And here’s a mock-up wall assembly by Hammer and Hand showing many of the details we incorporated into our own house:

While many believe a double stud wall simplifies much of the framing, we decided that a continuous insulation approach, which in theory should better manage seasonal moisture changes inside the walls while it also eliminates thermal bridges, was worth the extra effort.

2 Layers of Rockwool over Zip Sheathing

Based on the drawings from our original builder, Evolutionary Home Builders, who was going to use 3.75″ inches of rigid foam, and the recommendations of both PHIUS and Green Building Advisor for our climate zone 5 location (leaning heavily towards PH performance), we decided to go with 4″ of Rockwool Comfortboard 80 on top of our Zip Sheathing.

For more information regarding how we came up with the specifics of our wall assembly, go here:

Wall Assembly

Finding Subcontractors for a Passive House

In the Chicagoland area it’s still a struggle to find builders or subcontractors who are knowledgable about, or even interested in, “green building”. In fact, despite our well-documented experience with Evolutionary Home Builders, clients continue to hire Brandon Weiss (Dvele and Sonnen) and Eric Barton (apparently now on his own as Biltmore Homes, or Biltmore ICF) presumably because the options here in Chicago remain so limited. We assume this is the case because we still get the occasional email from current or former clients who have also had a negative experience working with Brandon or Eric. In addition, even though PHIUS has dozens of certified builders and consultants listed for Illinois and the larger Midwest region, it’s unclear just how many of them have worked directly on an actual Passive House project.

Until there’s more demand from consumers, or the building codes change significantly, it’s difficult to imagine the situation improving much in the near future. This is unfortunate since particularly here in the Chicago area, or the Midwest more broadly, homes could really benefit from the Passive House model, or something close to it, e.g. The Pretty Good House concept, because of our weather extremes (dry, cold winters and hot, humid summers). The combination of meticulous air sealing, high R-values, and continuous ventilation associated with any high-performance build is hard to beat in terms of day-to-day occupant comfort, not to mention the significant reduction in both overall energy demand and the cost of utilities.

In our own case, when I think of all the individual trades we had to hire, securing a siding contractor was far and away the most difficult. Our HVAC contractor for the ductless mini-splits was already somewhat familiar with “green” building and PH, so working with me on air sealing details and dealing with a thick wall assembly didn’t worry him. Also, if I had it to do over, I don’t think I’d bring up all the PH details with a plumbing or electrical contractor when getting bids since the air sealing details are pretty straightforward and can easily be planned for and executed on-site after they begin their work (assuming someone else, most likely a rough carpenter, GC, or homeowner is tasked with all the air sealing chores). And if the concrete sub is unfamiliar with insulation under a basement slab, or over the exterior walls of the foundation, then it’s easy enough for framers, or even homeowners if necessary, to do this work, along with installing a vapor barrier like Stego Wrap before the basement slab gets poured.

For siding, however, because of the level of detail involved before the siding itself could be installed, it was a real challenge to even get quotes. As things turned out, we had nearly twenty contractors (a mix of dedicated siding contractors and carpenters) visit the job site before we received an actual estimate. Many of those who visited the job site expressed genuine interest, most going so far as to acknowledge that this kind of wall assembly made sense and would probably be mandated by the residential code at some point in the future, but almost without exception they would disappear after leaving the job site — no bid forthcoming, and no response to my follow-up phone calls or emails.

Clearly they were terrified, not without justification, to tackle something so new, viewing our project through a lens of risk rather than as an opportunity to learn something new. From their point of view, why not stick with the type of jobs they’ve successfully completed hundreds of times in the past? It also didn’t help that I was a first time homeowner/GC, rather than a GC with a long track record of previously built homes in the area.

In addition, not only is continuous insulation over sheathing a novel concept in the Chicago area, especially in residential builds, even utilizing a ventilated rainscreen gap behind siding is almost unheard of — typically Hardieplank lap siding is installed directly over Tyvek or similar housewrap (this can be observed directly on hundreds of job sites across the city and suburbs). And this isn’t entirely the fault of contractors. For instance, how many homeowners when presented with the idea of continuous insulation, or a rain screen gap, balk at the extra costs associated with these techniques without carefully considering the potential energy savings or increased durability for the structure?

While there are any number of certified LEED projects in our area, and even some Passive House projects (both residential and commercial) in Chicago and the surrounding suburbs, for the most part consumers are still largely unaware of Passive House or other “green” building standards like Living Building Challenge. Clearly “green” building, let alone Passive House, has its work cut out for it here in the Midwest if it ever hopes to have a meaningful impact on the construction industry.

Installing Rockwool over the Zip Sheathing

Mike Conners, from Kenwood Passivhaus, was nice enough to recommend Siding and Window Group, which definitely got us out of a jam. Thankfully, Greg, the owner, was up for the challenge and was nice enough to let us work with two of his best guys, Wojtek and Mark.

Initially Wojtek and Mark dropped off some of their equipment at the site the day before they were to start work on the house. This gave me a chance to go through many of the details with them directly for the first time. Although a little apprehensive, they were also curious, asking a lot of questions as they tried to picture how all the elements of the assembly would come together. In addition to the construction drawings, the series of videos from Hammer and Hand regarding their Madrona Passive House project were incredibly helpful (this project in particular was a big Building Science inspiration for us).

Also, this video from Pro Trade Craft helped to answer some of the “How do you…?” questions that came up during the design and build phases:

As sophisticated and intricate as some architectural drawings may be, in my experience nothing beats a good job site demonstration video that shows how some newfangled product or process should be properly installed or executed.

On the first day, while Wojtek and Mark installed the Z-flashing between the Zip sheathing and the foundation, along with head flashings above the windows and doors, I started putting up the first pieces of Rockwool over the Zip sheathing.

installing head flashing above wdw
We found it easier to embed the metal flashings in a bead of Prosoco’s Fast Flash. Once in position, an additional bead of Fast Flash went over the face of the flashing, ensuring a water tight connection between the metal and the Zip sheathing.

For the first layer of Rockwool we installed the pieces horizontally between studs as much as we could, knowing that the second layer of Rockwool would be oriented vertically. This alternating pattern helps to ensure seams are overlapped between layers so there aren’t any areas where the seams line up, an outcome that could undermine the thermal performance of the 2 layers of Rockwool.

z flashing nw corner
Z-flashing carried down over the exposed face of the Rockwool on the outside of the foundation walls — once installed, the gravel is pushed back so it covers the area where the flashing terminates on the face of the Rockwool. The other 3 sides of the house had much less exposure in this foundation-gravel border connection.

We didn’t worry too much about the orange plastic cap nails missing studs since they were sized to mostly end up in the Zip sheathing. In the end only a couple of them made it completely through the Zip without hitting a stud.

1st pcs rockwool going up n side
Putting up the first pieces of Rockwool on the north side.

Every so often Wojtek would come around the corner and watch what I was doing before asking questions about specific elements in the wall assembly.

orange cap nails for 1st layer rockwool
Plastic cap nails we used to attach the first layer of Rockwool. I purchased these from a local roofing supply house.

By the time I had about a quarter of the north side covered, Wojtek and Mark were ready to take over from me.

1st layer rockwool n side
First layer of Rockwool mostly complete on the north side. Before installing the bottom row of Rockwool we used shims to create a slight gap between the Rockwool and the metal Z-flashing on the foundation insulation to allow any water that ever reached the green Zip sheathing a clear pathway out.

In a pattern that would repeat itself with each layer of the remaining wall assembly, Wojtek and Mark would carefully think through the details as they progressed slowly at first, asking questions as issues arose, before getting the feel for what they were doing and eventually picking up speed as they progressed around each side of the house.

20171002_081038
Outside corner showing the Z-flashing covering the face of the Rockwool on the foundation with the first layer of Rockwool covering the Zip sheathing above.

Working through the many details with Wojtek and Mark — the majority of which occur at junctions like windows and doors, the top and bottom of the walls, along with mainly outside corners — was both collaborative and deeply gratifying. They demonstrated not only curiosity and an ability to problem solve on the fly, they also clearly wanted to do things right, both for me as a customer and for the house as a completed structure (it felt like both aesthetically and in building science terms).

1st layer rockwool at wdw buck
First layer of Rockwool meeting up with a plywood window buck. We tried to keep connections like these as tight as possible, especially since the window buck itself already represents a slight thermal bridge.

They never hurried over specific problem areas, arrogantly suggesting they knew better, instead they patiently considered unanticipated consequences, potential long-term issues, and actively questioned my assumptions in a positive way that tried to make the overall quality of the installation better. This mixture of curiosity, intelligence, and craftsmanship was a real pleasure to observe and work with.

starting 2nd layer rockwool n side
Mark and Wojtek beginning the second layer of Rockwool on the north side.

If a GC built this level of rapport with each subcontractor, I can certainly understand their refusal to work with anyone outside of their core team — it just makes life so much easier, and it makes being on the job site a lot more fun.

2nd layer rockwool at utilities
Second layer of Rockwool installed around mechanicals. Note the sill cock, or hose bibb: although it runs into the house, we left it loose so that it could be adjusted until the siding was complete — only then was it permanently soldered into place.
weaving outside corner w: 2nd layer
Weaving the seams at the outside corners to avoid undermining the thermal performance of the Rockwool.
2nd layer rockwool fastener at wdw
Close-up of the fasteners we used to attach the second layer of Rockwool.

For the second layer of Rockwool, Wojtek and Mark tried to hit only studs with the black Trufast screws. In fact, screwing into the studs with these fasteners, in effect, became a guide for accurately hitting studs with the first layer of strapping.

plates for 2nd layer rockwool

These Trufast screws and plates worked well and were easy for Wojtek and Mark to install.

trufast screw bucket
inside bucket trufast screws
The Trufast screws and plates were purchased from a local roofing supply house.
w side 2 layers rockwool
West side of the house with 2 layers of Rockwool complete.
1st layer rockwool into s side garage
First layer of Rockwool filling the gap between the house and garage framing.

If our lot had been larger, we would’ve gone with a completely detached garage, but unfortunately it just wasn’t an option.

2nd layer rockwool closing gap at garage
Second layer of Rockwool closing the gap between house and garage completely, ensuring our thermal layer is unbroken around the perimeter of the house.
nw corner 2 layers rockwool
Northwest corner of the house with the 2 layers of Rockwool installed.

It was exciting to see the house finally wrapped in its 4″ of Rockwool insulation.

Installing Battens and Creating our Rainscreen

Initially we were going to use 2 layers of 1×4 furring strips (also referred to as strapping or battens); the first layer installed vertically, attaching directly over the 2×6 framing members through the 2 layers of Rockwool and the Zip sheathing, with the second layer installed horizontally, anticipating the charred cedar that would be oriented vertically on the house.

Pro Trade Craft has many really informative videos, including this one on using a rainscreen behind siding:

Nevertheless, as the second layer of Rockwool went up, Wojtek and Mark pointed out that putting the siding in the same plane as the Rockwool/metal flashing on the basement foundation would be needlessly tricky. In other words, maintaining about a 1/8″ horizontal gap between the bottom edge of the vertical siding and the metal flashing on the foundation around the house would be nearly impossible, and any variation might prove unsightly.

As a solution, we decided to use 2×4’s for the first layer of strapping. By adding to the overall thickness of the remaining wall assembly it meant the eventual siding — now pushed slightly out and farther away from the Z-flashing covering the face of the Rockwool on the foundation — could be lowered so that visually it slightly covered what would’ve been a gap between the top of the metal flashing on the foundation insulation and the bottom edge of the siding. Wojtek and Mark also found that the 2×4’s were easier to install than the 1×4 furring strips directly over the Rockwool so that it didn’t overly compress the insulation (an easy thing to do).

Unfortunately, increasing the overall wall thickness with 2×4’s meant having to use longer Fastenmaster Headlok screws (it would also cost us later when it came to the siding on the north side of the house — more on this later). Apart from this change, the additional overall wall thickness mostly just increased the air gap in our rainscreen, which arguably just increased potential air flow while also expanding the drainage plane behind the eventual siding.

In one of the Hammer and Hand videos Sam Hagerman mentions that at least 1.5″ of screw should be embedded into the framing (excluding the thickness of the sheathing) for this type of wall assembly, but when I asked a Fastenmaster engineer about this directly he recommended a full 2″ of their screws should be embedded into the framing members in order to avoid any significant deflection over time.

As a result, we ended up using 8.5″ Headlok screws. The screws work incredibly well, requiring no pre-drilling, and they’re fun to use with an impact driver (keep your battery charger nearby). Along with the plastic cap nails and Trufast screws, I think we ended up with less than a dozen fasteners that missed the mark for the entire house — a testament to Wojtek and Mark’s skill. I was able to seal around these errant fasteners from the inside with a dab of HF Sealant.

headlok missed framing
Sealing around a Headlok screw that missed a 2×6 framing member.

During the design stage, using these longer screws prompted concerns regarding deflection, but based on this GBA article, data provided by Fastenmaster, along with some fun on-site testing, the lattice network of strapping (whether all 1×4’s or our mix of 2×4’s and 1×4’s) proved to be incredibly strong, especially when the siding material is going to be relatively light tongue and groove cedar.

For the garage, since insulation wasn’t going to cover three of the walls (only the common wall with the house was treated as part of the house wall assembly), we used significantly shorter Headlok screws for the first layer of furring strips.

monkey on furring strips
The Beast testing out the structural integrity of our strapping on the garage. Note the Cor-A-Vent strip below the bottom horizontal furring stip, helping to establish a ventilated rainscreen.
garage only 2x4s
Common wall inside the garage. Only a single layer of strapping was necessary in preparation for drywall.

Mark took the time to recess these screws to make sure they didn’t interfere with the eventual drywall.

recess 4 screws
Recessed Headlok screw on a 2×4 in the garage. Ready for drywall.

A small detail, but one of many examples showing Wojtek and Mark’s attention to detail, not to mention their ability to properly assess a situation and act appropriately without having to be told what to do.

Once the 2×4’s were all installed vertically through the structural 2×6’s as our first layer of strapping, Wojtek and Mark could install the components of the rainscreen, including the Cor-A-Vent strips at the top and bottom of the walls, as well as above and below windows and doors. In combination with the 2×4’s and the 1×4’s, this system creates a drainage plane for any water that makes its way behind the siding, while also providing a space for significant air flow, speeding up the drying time for the siding when it does get wet.

rainscreen2.jpg
Why use a rainscreen? Illustration courtesy of Hammer and Hand.

In addition to the Cor-A-Vent strips, we also added window screening at the bottom of the walls just as added insurance against insects. We noticed that on the garage, even without any insulation, the Cor-A-Vent didn’t sit perfectly flat in some areas on the Zip sheathing. Since the Rockwool on the foundation, now covered by the metal flashing, was unlikely to be perfectly level, or otherwise true, along any stretch of wall, it made sense to us to double up our protection in this way against insects getting into the bottom of our walls at this juncture.

starting 1x4s n side
1×4’s being installed horizontally on the north side in preparation for the charred cedar that will be installed vertically. Also note the Cor-A-Vent strips just above the foundation and below the window.
cor-a-vent-product-label
The main product we used to establish our ventilated rainscreen.
insect screen for rscreen
Window screen we cut to size for added insurance at the bottom of the walls around the Cor-A-Vent strips.

Wojtek and Mark also did a nice job of taking their time to shim the 1×4 layer of furring strips, thus ensuring a flat installation of the charred cedar.

shims behind 1x4s
Shims behind some of the 1×4 furring strips to ensure a flat plane for the vertical cedar siding.

This really paid off, not only making their lives easier when installing the tongue and groove cedar, but also providing aesthetic benefits in the overall look of the siding. This was especially true on the north side of the house, which has the largest area of charred siding with almost no interruptions, apart from a single window. It’s also the tallest part of the house, so without proper shimming the outcome could’ve been really ugly. Instead, once the cedar siding was installed it was impossible to tell there was 4″ of Rockwool and 2 layers of strapping between it and the Zip sheathing.

Really impressive work by Wojtek and Mark.

lking down furring behind rscreen at fdn
Looking down behind the ventilated rainscreen — 2×4, 1×4, with Cor-A-Vent and window screen at the bottom, just above the top of the foundation. This gap behind the siding provides ample air flow for the cedar siding, ensuring that the wood never remains wet for long.
rscreen furring at foundation
Strapping and rainscreen elements around a penetration near the top of the foundation.

Things got somewhat complicated around windows and doors, but once we worked through all the details for one window it made the remaining windows and doors relatively straightforward to complete.

Below you can see all the elements coming together: the window itself, the window buck covered with tapes for air and water sealing, the over-insulation for the window frame, the Cor-A-Vent strip to establish air flow below the window and behind the eventual cedar siding, along with the strapping that both establishes the air gap for the rainscreen while also providing a nailing surface for the siding.

Once most of the siding was complete around each window, but before the 1×6 charred cedar pieces used to return the siding to the window frames were installed, each window received a dedicated metal sill pan. The pan slid underneath the bottom edge of the aluminum clad window frame and then extended out just past the edge of the finished siding (I’ll include photos showing this detail in the next blog post about installing the charred cedar siding).

Here’s a JLC article discussing a couple of options for trim details in a thicker wall assembly with similar “innie” or “in-between” windows:

Window Trim

And here’s a detailed slide presentation by Bronwyn Barry regarding details like these for a Passive House wall assembly:

Sills and Thresholds – Installation Details
wdw rscreen and frame detail
The many details coming together around a window. In addition, each window eventually received a dedicated metal sill pan as a durable way to ward off water intrusion.
from int wdw rscreen and sill
Looking through an open window to the sill and the rainscreen gap at the outside edge. Note the Extoseal Encors protecting the sill of our window buck.
lking down wdw rainscreen
Outside edge of the window sill, looking down into the mesh of the Cor-A-Vent strip with daylight still visible from below.
rscreen at hd flash on wdw
Head flashing at the top of a window with doubled up Cor-A-Vent strips above it.
out corner hd flshng ready for sd
Same area, but with a 1×4 nailed across the Cor-A-Vent, creating a nailing surface for the cedar siding.

Many of the same details were repeated at the top and bottom of our two doorways. Below is a close up of the kitchen door threshold with Extoseal Encors and Cor-A-Vent again, along with additional metal flashing. Once a dedicated metal sill pan was installed (after most of the siding was installed), it felt like we did everything we could to keep water out.

kitch dr prepped 4 sd
Many of the same air and water sealing elements and rainscreen details present around the windows ended up at the top and bottom of doors as well.

In the photo below, you can see the many elements we utilized to try and prevent moisture damage around the front porch. For the door buck itself, I applied Prosoco’s Joint and Seam, both at joints in the plywood and the plywood/Zip sheathing connection, but also between the concrete and the door buck, as well as between the Rockwool and the concrete. We also kept the 2×4’s off the concrete, while also using the Cor-A-Vent strips to establish a ventilated rainscreen so that any moisture that does get behind the siding has ample opportunity to dry out in this area before it can cause any rot.

frt porch prep - rscreen water
Front porch: elements in place to try and prevent moisture damage.
west w: 2 layers battens
West facade prepped for siding.
flashing details on porch
Wojtek and Mark did a nice job with all the metal flashing details around the house — these kind of areas are the unsung heroes of a structure that manages water safely, and unfortunately go largely unnoticed by most homeowners.

In the next blog post I’ll go through the details for the top of the ventilated rainscreen when discussing how the charred cedar siding was installed.

Mark and Wojteck at front door
Mark and Wojtek installing Cor-A-Vent above the front door.

Even without the siding installed yet, it was especially rewarding to see all the underlying prep work involved in finishing our thermal layer and rainscreen come together so nicely.

Mark and Wojtek on the roof
Mark and Wojtek on the garage roof finishing up the battens for the front of the house.

Many thanks to Wojtek and Mark for executing all these details with such skill!