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HVAC (Part 1 of 2): Zehnder ERV

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Building with Passive House principles in mind, we knew that, in addition to maintaining a tight building envelope, and incorporating substantial amounts of insulation around the structure, we also needed to install continuous mechanical ventilation in order to have adequate levels of fresh air, not to mention the ability to expel stale air.

We also needed our system, either an HRV or an ERV, to be highly efficient, meaning it could hold onto some of the heat in the conditioned air even as it introduced fresh and, oftentimes, cold air by means of heat exchange as the two streams of air (fresh and stale) passed by one another inside the main unit (without actually mixing together).

After researching the many options, we ended up going with Zehnder’s ERV, in our case, the ComfoAir 350 (the various Zehnder units are based on overall cfm demand of the structure).

We only considered two other brands for our mechanical ventilation (HRV vs. ERV):

UltimateAire

and

Renewaire

In all the research I did prior to construction, it was these three brands that showed up the most in the projects I read about.

Here’s a good debate on the Green Building Advisor website discussing brand options: ERV Choices

Another interesting option would be the CERV system. Because they’re a smaller, newer company, we didn’t feel comfortable pursuing it, but it does look like a viable option worth considering if building a Passive House or Pretty Good House.

I was also familiar with Panasonic units, but I had always read that they weren’t efficient enough in terms of the heat exchange function (or heat recovery) to seriously consider using it in a Passive House or a Pretty Good House in a predominantly cold climate region like ours here in the Chicago area.

Our Zehnder ComfoAir 350 is said to be 84% efficient in terms of heat recovery (the same principle applies in summer, only working in reverse, when you’re trying to hold onto cooled, conditioned air). Based on what I read during the design phase, the consensus seemed to be that, although more expensive, the Zehnder has a strong track record of performance and durability.

The Zehnder also came with its own ductwork, which we knew would simplify installation, allowing us to do it ourselves, rather than hire someone else to come in and run more conventional ductwork through the house (conventional ductwork would’ve taken up a lot more space as well). Even though the unit itself was more expensive, we thought we could offset some of the total cost for a ventilation system by installing the Zehnder ourselves, thereby saving some money on labor costs.

As far as the ERV/HRV debate for Northern US states, we decided to opt for the ERV because it was supposed to help us hold onto some humidity in winter months, especially important when most structures in the Chicago area are exceedingly dry for most of the winter (and our winters are long). Although I read repeatedly during the design stage that ERV’s can also help control summer outdoor humidity entering the house, this has not been our experience at all. In fact, the ERV seems pretty useless in this regard (more on this below).

The system quote we received was easy to understand, and Zehnder was nice enough to essentially design the system, both in terms of layout (i.e., where we should put all the supply and exhaust points), along with the quantity, or cfm’s, of air for each point. In the end, after commissioning the unit, the system should be balanced, meaning the unit should be bringing in as much fresh outdoor air as it is expelling stale indoor air.

As far as Zehnder units being DIY friendly in terms of installation, in our opinion, this is highly debatable since the installation manual is far from comprehensive. Our installation manual ended at physically installing the main unit on the wall. Not very helpful.

Without a detailed installation manual showing step-by-step how all the individual pieces fit together, you end up with a pile of what initially seems like random parts.

zehnder pile of parts

Everything we need to install our Zehnder ERV. Most of the smaller components are still in the many cardboard boxes off to the right.

This was incredibly frustrating, especially since Zehnder units are purchased at a premium when compared to other competitive brands, and with the expectation of durability and design precision. It never occurred to me to ask before purchasing the unit for an installation manual, since it seemed a fair assumption that no one would sell a premium product without detailed instructions on how to put it together.

We were only able to proceed because of numerous online videos, googling Zehnder unit photos, and by staring at and experimenting with the various parts to try and figure out how it all was supposed to come together. It was an unnecessary and torturous puzzle that shouldn’t have needed solving, and it wasted hours of my life that I’ll never get back. If you do an internet search and type in: “google review Zehnder America” the experience Sean Hoppes had with his installation wasn’t all that different from ours.

Looking on the current Zehnder website (February, 2019), I can’t find a more detailed set of instructions, either written or in a video format, which is disappointing. This seems like a pretty glaring oversight on Zehnder’s part, and one that should be remedied immediately.

Having lived with the unit for almost a year now, overall we’re happy with its performance, and we feel like we could install one fairly easily now that we’ve gone through the entire process, so it’s a shame we can’t say only nice things about the product simply because the installation manual was so limited or, more to the point, non-existent.

With each video and each photo, it was possible to glean one more crucial nugget of information, which took hours, whereas a detailed written manual or a step-by-step video would’ve made the process straightforward, and by comparison, frustration-free.

The videos below were especially helpful, but, nevertheless, they still leave out quite a bit of pertinent information necessary for any first-time installer (especially regarding all the parts that need to be installed on top of the main unit):

 

Unless there are no DIYers in Europe installing these units, and this is the expectation Zehnder has for its units both for overseas and here in the US, not having a comprehensive installation manual makes no sense. I’m not sure how even a licensed and competent HVAC installer would fare much better without direct experience installing the units. My guess is they would be searching online for missing info much like we did.

Once we got the main unit installed on the wall, and we figured out how all the parts fit together on top of the unit, by the time we got to installing the small, white 3″ ComfoTubes and the large, gray ComfoPipe, the process became much easier.

main unit attached to basement wall

Mounting the main unit to the basement foundation wall with Tapcon concrete screws.

In regards to the gray ComfoPipe for the main fresh air supply and the main exhaust, both of which pass through the wall assembly, we found it more effective to put individual sections together on the floor, and, once fully connected, we marked the points at which the pipes met with a permanent marker.

marking comfopipe w: sharpie

Marking sections of connected ComfoPipe with a Sharpie while they’re on the floor ensures a tight fit once a connection has been made off the floor.

If you try to piece the tubes together one piece at a time in mid-air it’s much harder to gauge when the pieces are actually tightly put together. With each connection point of pipe clearly marked with a Sharpie, it gives you an obvious goal to shoot for once you have the pipe almost in its final position. More to the point, it’s obvious when sections of pipe get out of alignment, or the connection isn’t nearly tight enough — it’s much more difficult to accurately gauge if only going by “feel” once the sections of ComfoPipe are off the floor.

drilling hole for Zehnder exhaust

Making initial cut in the Zip sheathing.

Using a piece of ComfoPipe, we outlined on the interior side of our Zip sheathing exactly where we wanted the pipe to end up (trying to get as close to center as possible — makes air sealing around any penetration much easier). After a hole was cut with a 3″ hole saw, we cut out the rest of the hole using a jigsaw.

hole in Zip for heat pump pvc

Hole cut and ready for the ComfoPipe.

 

hole set-up for comfopipe

Hole made in our Zip sheathing, ready for the ComfoPipe from outside to make a connection with the section inside.

 

ext - comfo pipe going thru zip into basement

Ready to push the ComfoPipe into the house from outside to make the connection inside.

 

Zehnder chipmunk's back

Chipmunks are back.

Once we started using the Sharpie, it was relatively easy to get all the ComfoPipe installed and air sealed around the Zip sheathing.

comfo pipe thru zip

Making the connection between inside and outside.

 

setting up comfo pipe

Adding a Roflex gasket to make air sealing much easier.

 

comfo pipe sealed int.

ComfoPipe air sealed on the interior side with Roflex gasket and Tescon Vana.

 

close up comfopipe sealed

Close up of the ComfoPipe air sealed at the Zip sheathing.

 

installing comfo pipe next to main unit

Finishing up the last sections of ComfoPipe as they leave the main unit.

Following the directions, we kept the ComfoPipe exit points for supply and exhaust more than 10′ apart outside, where they enter and exit the structure, in order to avoid any possibility of the two air streams mixing, which would undermine the effectiveness of the system.

comfopipe ext sealed and covered

Repeating the same air sealing process on the exterior for the ComfoPipe, adding black garbage bags over the opening with rubber bands to keep out dust, dirt, birds, and any critters that might otherwise try to enter the structure during construction.

On the outside, we made sure to extend the ComfoPipe out farther than we needed, giving us some leeway once insulation and siding were installed over the Zip sheathing. This allowed us to cut the ComfoPipe back to the proper depth before installing the permanent covers supplied by Zehnder.

comfo pipe ext close up sealed

Close up of ComfoPipe as it exits the structure (before insulation, furring strips, siding, and its final cover).

As far as the white tubing is concerned, we really enjoyed how easy it was to put the 3″ ComfoTubes together.

During the design phase, and even after we brought the Zehnder unit to the job site, we always intended to place the diffusers for supply and exhaust points on ceilings. But after really looking at all the cuts in our ceiling service chase that would be required to make this happen, we decided to opt for placing all of them on walls instead.

It proved to be one of the better decisions we made during construction. Not only did we avoid having to make many cuts in our ceiling structure, which would’ve meant a struggle to appropriately map them out around conduit, ceiling lights, and plumbing vents, it had the added benefit of making it much easier to do ongoing maintenance at the diffusers, mainly checking on and cleaning filters, once we moved in.

cone diffuser filter

Cone shaped filter for exhaust diffusers (bathrooms, kitchen, laundry room, and basement in our case).

In fact, during commissioning, our Zehnder rep told me they have issues with homeowners not keeping their exhaust diffuser filters properly cleaned, effectively undermining the efficiency and overall performance of the units. This is understandable if the diffusers are on ceilings, whether at 8′ or 9′. It would be easy to forget about them, or even if you did remember, one can understand the reluctance to drag out a 6′ step ladder every time they needed to be cleaned. We were also told that placement of the diffusers is extremely flexible — almost anywhere can work (check with Zehnder directly just to make sure your proposed placement will work).

inside diffuser filter

Diffuser filter in bathroom after about a month. Once all the construction dust settled down from completing interior finishes, these filters don’t get dirty nearly as quickly as they once did — in other words, this isn’t bad at all.

By keeping them around 7′ off the finished floor, it’s easy for me to check and clean the exhaust diffuser filters on a regular basis (1-2) times a month. I always have 2 sets of filters, so it’s easy to remove the dirty ones, put in clean ones, and then rinse and dry out the dirty ones.

Once we decided to go through walls (both 2×6 and 2×4 framed walls), it was just a matter of deciding where in each wall we wanted the diffusers to be placed, and then cutting the corresponding hole through the wall’s bottom plate and the subfloor — being careful to check, and re-check, in the basement for any floor joists, plumbing, or electric conduit that might be in the way.

For bathrooms we placed the diffusers between showers and toilets, slightly cheating towards the showers to ensure maximum moisture removal.

changa drilling for tubes

Apparently cutting the holes through the floor looked like fun, since my wife was happy to take over this chore for me. The DeWalt we were using worked great until it crapped out on us a couple of holes short of finishing. We definitely noticed a difference going back to a normal drill and hole saw set-up.

At the unit itself, Zehnder supplied us with blue (fresh air) and red (stale air) tags, to mark each ComfoTube as it leaves or returns to the main unit. This should make any potential maintenance or repair issues in the future easier to resolve, as well as helping to avoid confusion as you set in place each pipe at a diffuser.

first few return tubes are in

Attaching the white ComfoTubes to the main unit, carefully labeling each pipe for future reference.

 

main unit w: exhaust tubing installed

ComfoTubes being installed at the main unit.

 

top of silencers #2

Close up of the top of the main unit, as ComfoTubes are being installed.

 

Sydney helping us

Sydney, one of our former Excel students, was nice enough to stop by and help us pull the ComfoTubes from the basement up to the first floor.

 

OB helping us pull and set-up the tubes

OB was also nice enough to come back to help us push and pull the ComfoTubes into place for the diffusers.

 

spaghetti

Pulling more tubing than we need up to the first floor. Later it’s cut back to properly fit to the various diffuser boxes.

 

setting up a port

Putting together a diffuser box.

Since we’re leaving the basement ceiling unfinished, it’s an ideal place to see how all the components come together: ComfoTubes meet at the diffuser box, along with the final cover for the diffuser, in this case for supply air. As you can see in the photo, there’s plenty of room in the metal tube of the diffuser box for deciding exactly where to cut it off in order to establish the finished height for the diffuser cover. In the basement we left them at their full height since there didn’t seem to be much incentive to cut them back.

basement supply diffuser

Basement diffuser box with attached ComfoTubes and final diffuser head (supply in this case).

 

laundry rm zehnder

Exhaust point in utility room with only one ComfoTube.

All of the diffuser boxes required at least 2 ComfoTubes, except for the laundry/utility room, which only required one. Using one of the supplied black plastic caps made it easy to block off one of the outlets in the diffuser box. These black caps are also handy when pulling the ComfoTubes around into position since they help to keep out any construction debris.

laundry rm exhaust

One outlet in the diffuser box is blocked off for the laundry room since we only required 12cfm for this area (12cfm per opening/ComfoTube).

Our kitchen required the most cfm’s, at 36, so it required a special diffuser box and 3 ComfoTubes.

kitchen octopus

3-hole diffuser box (36 cfm) for kitchen exhaust.

Again, since we didn’t place it in the ceiling, we put it across the kitchen, basically on a diagonal from the stove. So far we haven’t had any issues with cooking grease or odors, and our range hood (recirculating) seems to be doing its job just as well.

sunlight coming down comfo tubes

Sunlight coming down the ComfoTubes into the basement from the main floor.

Using scrap lumber, we were able to give each diffuser its proper stability in the wall cavities. Although the mounting hardware for each diffuser box seems rather fragile, we managed to avoid any issues.

Applying a bit of hand soap around each opening in a diffuser box made getting a solid fit between the ComfoTube, the black O-ring, and the diffuser box fairly straightforward.

connecting tube in kitchen

Attaching ComfoTubes with black O-rings and sliding clips on the diffuser box.

 

tubes for octopus in kitchen

ComfoTubes for kitchen exhaust going through the subflooring and into the basement.

 

black 0 ring

Putting the black O-ring on the ComfoTube.

It was also fairly easy to get each ComfoTube exactly where we wanted it. Since they’re so small (at least compared to traditional sheet metal ductwork), the tubes are easy to manipulate and move around, whether over a basement beam, around plumbing, electric, or any other structural component that’s not easily relocated. As long as you don’t need to make a short 90° turn, the tubes are easy to work with, so I imagine they would be ideal for renovation work in older homes.

long shot before tightening comfo tubes

It was fairly easy to put the ComfoTubes exactly where we needed them to go.

With most of the ComfoTubes in place, we just needed to add a couple of walls in the basement before finishing up the last few ComfoTubes.

raising basement wall w: Jesus and Eduardo

Jesus and Eduardo were nice enough to come back to help me put up a couple of basement walls.

Once all the ComfoTubes were installed at all the diffusers and at the main unit in the basement, we were able to pull all the lines tighter for a less messy final installation.

spaghetti comfotubes

Before pulling the tubing tight.

Using 2×4’s, we created a little window for the ComfoTubes to pass through under the floor joists. This structure helped to get the ComfoTubes moving away from the main unit in an orderly way that made it much easier to organize all the tubing once it was all installed.

zehnder installed w: tubes

All the ComfoTubes pulled tight, up by the floor joists, kept in place with some plumbing hangers.

Using plumbing hangers also kept the ComfoTubes under control and organized.

hanger straps for comfo tubes

Straps used to corral the sometimes unwieldy ComfoTubes, which can resemble spaghetti if left unorganized. They also worked well at stabilizing the gray ComfoPipe.

The commissioning of the unit, after drywall was complete, was fairly easy and straightforward, apart from a couple of wiring and electrical issues that had to be dealt with by phone with a Zehnder rep beforehand. And ordering filters from the Zehnder website has also been a straightforward and painless process so far (they’re not cheap, but they do seem to be highly effective).

The only issue we’ve really noticed with the unit is during summer when outdoor humidity levels are high. Since the ERV is constantly running, there’s no way to avoid bringing in some humid air in the summer.

And, unfortunately, it’s enough so that our Mitsubishi heat pump set-up (a future Part 2 of 2 for HVAC details) can’t properly get rid of the excess humidity either, even as it keeps the interior more than adequately cooled. We tried setting the heads to dehumidify, but they just dropped the temperature (almost to 60° F) without budging the humidity in the house very much — the rooms were freezing and clammy. As noted earlier, an ERV just can’t handle elevated levels of humidity in the summer on its own.

By having meters in various areas of the house it’s easy to see when humidity levels become a problem (we’ve been happy with our AcuRite gauges). Last summer our solution was to buy a couple of small dehumidifies, one for the first floor and one for the basement. They worked, but they also ate up a lot of energy. Setting the Zehnder fan speed to LOW seemed to help somewhat, but not enough to avoid using the dehumidifiers. This summer we’re going to try a stand-alone Ultra-Aire whole-house dehumidifier, which should use less electricity, and it should perform at least as well, if not better, at removing excess humidity.

 

Having read that anything above 60% indoor humidity can be problematic, especially in tighter, high-performance homes, it was disheartening to see the numbers move towards 70% in early summer. This is what prompted the purchase of the dehumidifiers.

From everything I had read during the design phase regarding Passive House, I knew indoor humidity in the summer could be a slight issue, but having experienced it firsthand, it now seems obvious that incorporating a dedicated dehumidifier in any structure that will see elevated levels of summer humidity, even if it’s only expected to last for just a few weeks, is simply a necessity. Based on what I’ve read recently, it sounds like Passive House designers, who were already doing this for Southern US states, are moving towards doing it in states much farther north. Presumably this would also hold true for anyone designing a Pretty Good House as well.

Granted, 60-70% indoor humidity (or even higher) for a couple of weeks probably won’t ruin any structure, but for us, at least, keeping it in the 50-60% range during the hottest days of summer not only gives us some added peace of mind, regardless of the hit we’ll take in terms of overall energy use, but it’s also an issue of comfort (I grew up in a house without air conditioning and still have vivid memories —all of them bad — of enduring hot and humid summer days and, even worse, long summer nights).

Much like the initial complaints of overheating, due to excessive or improper placement of glazing, especially on southern facades, this issue with excessive humidity seems to be part of the evolution in understanding how Passive Houses, or high-performance homes generally, actually work in real-world conditions. Although the concept has been around since the 1990’s, anyone building to or even just towards the Passive House standard should know they are guinea pigs to some extent, no matter how well established the idea may be in building science terms.

In the winter, we’ve had no issues. When temperatures fall below 20° F, we set the Zehnder to LOW, in the hopes that it will reduce demand on the heat pumps slightly, and it seems to hold onto humidity somewhat when the cold air being introduced would otherwise be excessively dry. Indoor humidity levels have been pretty consistent: above freezing they typically stay around 40%, and when temperatures plummet towards zero or below they’ve still stayed in the 30-35% range. We’ve rarely seen indoor humidity drop below 30%, even on the coldest days, which definitely makes a difference on overall comfort levels. I’ve also noticed that wood flooring and wood trim doesn’t shrink nearly as much as it did in our last, conventionally built home.

Also, even when we experienced record low temperatures last month (January, 2019), hitting -24° F without windchill, the Zehnder kept on running without any issues. As far as we know, it never shut off to try and protect itself from the cold (our mini-split system did, but more on that later). The product literature is somewhat vague, only noting that low temperatures could cause a unit to shut off, but it’s unclear at exactly what temperatures or what combination of other environmental conditions might cause this to happen.

Most people either tape or use sealant on the gray ComfoPipe seams to block air leakage. During our blower door test no air leakage showed up, even with a smoke pen test. Nevertheless, during our recent cold snap some frost was evident on the ComfoPipe seams, so I’ll eventually caulk these seams with Pro Clima’s HF Sealant, since there must be some air leakage, be it ever so minor.

In terms of the boost function, when turned on it pulls from all the exhaust diffusers, not just a particular bathroom or the kitchen. Again, for the kitchen, even if we’ve been roasting garlic or cooking something else that’s equally pungent, by the next morning any cooking smell is usually completely gone. There’s never been any lingering smells emanating from the kitchen.

For the kitchen, when you want to utilize the boost function you just set the ComfoSense wall unit to HIGH (the Zehnder equivalent to a standard wall thermostat). Unlike the bathroom boost switches, which run on a timer (set at the main unit in the basement), when you’re done cooking you have to remember to go back and lower the fan speed, otherwise it just stays on HIGH.

The ComfoSense unit also can display error functions or tell you when filters at the unit need to be cleaned. It also has an AWAY function, meaning you can have minimal fan speed to exchange air while you’re on vacation instead of just unplugging the unit altogether.

 

boost rocker switch

Boost rocker switch in the bathroom.

The boost switch in a bathroom is set to run for 30 minutes on the highest fan speed. So far, this seems to be plenty of time for it to work properly. Unlike a normal bath fan, which tends to be quite loud, even when the Zehnder is in boost mode it’s still incredibly quiet, so guests need to know they only need to press the switch once — it is indeed working.

For the bathrooms, the boost function has been working really well at removing moisture after showers. Nevertheless, in the winter, when temperatures are below 20° F and we decline to use the boost function after showers (again, hoping to hold onto some of the added humidity), the bathroom humidity levels still quickly drop from the 60’s and 70’s back to the mid-30’s in less than an hour (and this is even when the Zehnder fan speed is set to LOW).

We’ve also been happy with the diffusers, in terms of installing/removing them when necessary, but also in terms of their overall look. Whether on more neutral colored walls, or something bolder, they just look nice in our opinion.

supply diffuser

Zehnder supply diffuser on a neutral background on the wall.

They’re subtle enough to blend in to the background, but attractive enough so when they are noticed they don’t stand out in a negative way.

Zehnder exhaust diffuser

Utility room with a Zehnder exhaust diffuser on a neutral background — around the corner from the clothes dryer.

 

diffuser w: bold colors in bg

Zehnder supply diffuser on a much bolder background.

As far as changing filters at the unit, or even cleaning the core itself, so far it’s been a trouble-free experience.

Here’s a photo of a supply-side filter after one month of exposure in winter:

zehnder supply filter

A Zehnder supply-side filter (MERV 13) after 1 month in winter.

During the summer, of course, they look much worse after a month with so much more “stuff” floating around (pollen, debris from landscaping, insects, etc.). Also unsurprisingly, the exhaust-side filter always takes much longer to get dirty as stale air makes its way out of the structure (it probably helps that we don’t have any cats or dogs).

And since we didn’t need the framed-out HVAC chase in the corner of our Master Bath for all the ComfoTubes that we initially planned to send up into our ceilings, we ended up using this area for some much needed niche shelving for various toiletries and even some towels.

Overall, then, we’ve been extremely happy with our Zehnder ERV unit.

 

WRB: Zip Sheathing (Air Sealing #6 )

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Zip: Air Sealing the Seams and Penetrations

( Note: This post will concentrate on the Zip sheathing itself, as it relates to seams and penetrations. I’ll address how I sealed around openings for windows and doors, along with our attic access hatch through the Intello on the ceiling in separate, future blog posts.)

We used Zip sheathing as our WRB (water-resistant barrier — or sometimes it’s referred to as a weather-resistant barrier) based largely on Hammer and Hand projects,

and seeing it used on various jobs featured in Fine Homebuilding Magazine.

As the 7/16″ Zip sheathing went up, I taped most of the seams with Pro Clima’s  3″ Tescon Vana tape (available at 475 HPBS), but also their Contega tape (6″ wide), which I used mainly for outside corners and larger seams in the Zip (mainly where the horizontal seam in the Zip transitioned from the exterior walls of 2×6 framing to the roof trusses — shown in a photo later in this post).

My wife and daughter also cut up the Tescon Vana tape into small pieces in order to cover all the nail and screw holes in the Zip sheathing.

beast and eduardo taping nail holes

The Beast and Eduardo team up to tape the nail and screw holes on the lower sections of Zip sheathing around the house.

The nail holes were initially sealed with HF Sealant, also available from 475 HPBS, thus giving them double coverage — this was discussed earlier, here:

Framing (Air Sealing #2)

north side house garage gap long view

Northeast corner of the house where it meets the garage.

Our decision to use the Zip sheathing was also discussed earlier, here:

Wall Assembly

And here’s a good video discussing the Zip sheathing and its benefits (and its place in the evolution of building science):

If I had it to do over, I think I might be tempted to use 1/2″ exterior grade plywood as my sheathing (there are any number of WRB options these days). This would be sealed on the exterior side with either a liquid membrane, like Prosoco’s Cat 5, or a peel-n-stick tape like Henry’s Blue Skinor even another 475 HPBS product Solitex Mento 1000.

The Zip sheathing works, and the exterior green skin held up nicely during construction, even as it sat exposed for nearly 10 months after we fired our GC’s and struggled to keep the project moving forward. Nevertheless, it is little more than glorified OSB, which comes with certain inherent weaknesses.

Matt Risinger does an excellent job of delineating the cost/benefits of using either OSB or CDX plywood as a sheathing material:

 

house-garage-gap-for-4%22-roxul

Garage (at left) house (at right) connection. Gap will eventually be filled with 4″ of Roxul Comfortboard 80.

 

garage-house-gap-2

Closer view of this same garage – house connection. Flashing will cover the bottom of the Zip and then carry over the top of the Roxul that covers the foundation.

 

north-side-seams-taped

View of the north side of the house as Tescon Vana tape air seals the nail holes and the seams in the Zip sheathing.

View of the West facade with Tescon Vana tape, along with the black Contega tape at larger seams (e.g., where the walls meet the roof trusses) and outside corners.

west side being taped

West facade as taping proceeds.

 

taping north side before mechanicals : windows

Northwest corner of the house, transitioning from the Tescon Vana to the black Contega tape at the corner.

 

finishing up seams on west facade

Finishing up some of the final seams in the Zip on the West facade.

Once the Zip was fully installed, it was readily apparent that some of the seams, especially near the base of the first floor where a horizontal seam ran around the entire structure, would need to be tightened up.

Here’s a view looking down on one of these areas where the Zip sheathing did not sit flat against the framing members:

down Zip - out of alignment before 1x4's

Horizontal seam in Zip sheathing refusing to lie flat against the 2×6 framing members.

Using a 1×4 in each stud bay, I was able to pull the seam in the Zip sheathing together. It wasn’t always perfect, but the difference was visibly significant and in most areas well worth the effort.

Placing a 1×4 into position over the seam in the Zip, I would drive a couple of screws towards the exterior.

1x4 in study bay before HF

1×4 used to pull an unruly seam in the Zip sheathing together.

 

screw thru zip for 1x4 in stud bay

Screw from the interior poking outside as it initially gets the 1×4 in place.

Once securely attached from the interior, I went outside and drove several screws into the Zip, both above and below the seam in the Zip, to pull the seam tight to the 1×4. At that point, I could go back inside and remove the two screws that were driven towards the exterior.

In addition to air sealing the exterior side of the Zip sheathing, I also invested some time in air sealing the interior side of the Zip as well. Below is a long view of several stud bays with 1×4’s installed, but before air sealing gaps around the 1×4’s and lower areas of the stud bays with HF Sealant.

stud bays w: 1x4's, before HF

Long view after applying the HF Sealant:

ceiling walls - HF Sealant

Close up of the interior side of the Zip sheathing meeting a 2×6 framing member in a stud bay after applying a thick bead of HF Sealant:

thick bead HF sealant in stud bay

Close up of lower area of a stud bay after air sealing with the HF Sealant (it transitions from a light to darker green as it dries):

stud bay w: 1x4 and HF sealant

1×4 installed and HF sealant applied to all gaps and screw/nail holes in the stud bay.

I held off on using the HF Sealant at the wall sill plate/subfloor connection until just prior to installing the Intello on the walls since this area constantly attracts dirt and debris.

Sealing on the interior side with HF Sealant, even between vertical framing members, means that even if there are any weaknesses in either the Zip sheathing or the Tescon Vana tape at these points, air won’t find an easy way in, since it will be blocked from the interior side as well (there won’t be a difference in air pressure to help the outdoor air make its way indoors).

This kind of redundancy in air sealing should give the house long-term protection against air leaks, thereby aiding the long-term durability of the structure, as well as making it a much more comfortable environment to live in.

interior walls sealed w: HF sealant

Using HF Sealant between vertical framing members.

I also spent some time on the roof trusses, sealing around nails, the top plates of the exterior walls, and the many Zip-framing member connections in what will eventually be the attic.

sitting on roof trusses sealing

Sealing around fasteners and framing in the attic with HF Sealant.

This had less to do with air sealing and more to do with preventing any potential water intrusion since this area is technically above our ceiling air barrier (the Intello), which is detailed here:

Ceiling Details (Air Sealing #4)

 

 

 

Inventory of Penetrations through the Zip Air Barrier

I made a mock wall assembly before construction began, which I discussed here:

Wall Assembly

This proved helpful when explaining to the various subs how to help me protect the air barrier — especially when it came time to drill holes through the Zip sheathing. Of particular importance was making holes closer to the center of a stud bay, as opposed to hugging a corner or side of one of the 2×6 framing members. A hole cut too close to a stud or a roof truss is much harder to properly air seal.

bad-good-mock-wall-assembly-for-penetrations

Interior side of our mock wall assembly, showing how all penetrations through the Zip should be in the middle of our framing members. Our original plumber was the only trade that managed to screw this up (it’s no coincidence that he was also the only sub that we had to fire).

In effect, any time a sub had to make a penetration through the air barrier we discussed the details, and once the cut was made I immediately air sealed the penetration both on the exterior and interior side.

By sealing each hole in the Zip on both sides, again I hope it ensures the long-term durability of the overall structure. The main argument for this strategy assumes the exterior side of the sheathing will face more extreme temperatures, and fluctuations in humidity, and presumably even wind-drive rain if/when it gets past the siding and 4″ of Roxul insulation, putting it at greater risk of failure (especially in the long term). By taking the time to air seal the interior side, it just gives the overall air barrier, and therefore the structure, a better chance at avoiding air and water intrusion (that’s the goal anyway).

For air sealing I used a mix of tapes, HF sealant (later even some Prosoco products), EPDM Roflex gaskets, and duct seal.

The penetrations for electric service were my first go at using the Roflex gaskets.

John & Donny installing meter

John and Danny, from Chicago Electric, installing the electric meter.

The smaller diameter Roflex gasket comes with its own Tescon Vana tape, which makes installation straightforward.

close up meter thru Zip w: TVana gaskets

Electric meter with Tescon Vana – Roflex gaskets installed.

 

meter - hole, t. vana prior to appl.

Exterior view of electric Meter air sealed with gaskets and Tescon Vana tape:

electric meter close up gasket : t. vana

Once sealed on the exterior side, I went inside to seal the penetrations for a second time.

meter to panel - interior

Air sealing the electric meter on the interior side.

It was a big moment when the electric panel went in.

main panel in - progress

The house is ready for power.

The installation of our solar panels required air sealing two penetrations — one through the Intello on the ceiling on the inside of the structure, along with one exterior penetration through the Zip:

 

 

 

 

Details regarding the installation of our Solar array can be found here:

Solar on the Roof

corrected solar on:off

Solar disconnect (on/off) with its Tescon Vana gasket.

We also had two frost-free hose bibs, or sill cocks installed, which also required gaskets on the exterior and interior sides of the Zip sheathing.

hosebib w: gasket

Frost free hose bib with gasket.

One of the big advantages a Roflex gasket has over using a sealant like the green HF Sealant, or Prosoco’s Joint and Seam, is the pipe can be moved in and out even after air sealing, which is especially helpful for installing siding later.

We left the sill cocks loose (unconnected inside the house), allowing the siding guys to adjust in and out for a more precise fit of the charred cedar siding.

Below is an example of what conduit through the Zip sheathing looks like before it gets a gasket and tape:

exterior light conduit before gasket

Penetration for conduit before gasket.

And here’s the conduit after the gasket and tape.

gasket for exterior light

Conduit after gasket.

Note the extended length of the conduit, anticipating our 4″ of Roxul covering the Zip, 2-layers of furring strips (vertical then horizontal — for vertically oriented siding), and the eventual charred cedar siding.

The photo below shows the penetrations, along with multiple lines of conduit, for our eventual ductless mini-split Mitsubishi heat pump system. The empty hole will be our disconnect for the heat pump. I’ll go into the details of our ductless mini-split system in a future post.

conduit for heat pumps

Penetrations for our Mitsubishi heat pump system.

Same series of conduit pipes after gaskets and being connected to the compressor outside:

heat pump electric w: t. vana before disconnect

In addition to the conduit for electrical hook-up, the Mitsubishi heat pump system required a separate penetration for running the refrigerant lines to the compressor.

hole in Zip for heat pump pvc

Hole cut for the heat pump refrigerant lines.

After discussing it with Mike from Compass Heating and Air, who did our ductless mini-split installation, we decided to use a 4″ section of PVC plumbing pipe as our “conduit” for running the refrigerant lines from the interior of the structure to the outside.

heat pump - pvc pipe in hole for lines

4″ PVC plumbing pipe for the refrigerant lines.

After the PVC was passed through the hole in the Zip, we added a 2×4 underneath it to give it some added stability, along with the usual gasket and tape for air sealing around the PVC pipe.

heat pump - int side - pvc, gasket, 2x4

Before applying Tescon Vana around the Roflex gasket.

Once the refrigerant lines were passed through the PVC pipe, it was clear that some additional air sealing was required.

gaps around pvc lines before duct seal

PVC pipe with refrigerant lines installed.

I filled the gaps around the refrigerant lines from the interior and exterior sides with duct seal. Before stuffing in the duct seal at either side of the PVC pipe, I added bits of Roxul Comfortboard 80 into the pipe to try and give added R-value to the interior of the PVC pipe (hoping to prevent any possible condensation from forming inside the pipe).

duct seal label

A real life saver when it comes to air sealing. Readily available at big box stores, or online at Amazon.

Duct seal proved especially helpful at air sealing multiple weak points in the structure —areas that would’ve been difficult or impossible to air seal with just tape, gaskets, or sealants.

heat pump pvc w: duct seal close up interior

Using duct seal to block off air from the interior side.

 

heat pump pvc w: gasket before t. vana close up

Another view of the PVC pipe with duct seal.

 

heat pump refrigerant lines - int. leaving basement

The refrigerant lines transitioning from the basement ceiling to the PVC pipe before leaving the structure.

Once the interior was taken care of, I was able to address the exterior side of the PVC pipe:

heat pump lines before tape after duct seal

Exterior view of the PVC pipe with heat pump refrigerant lines exiting the structure, being air sealed with a Roflex gasket and duct seal inside the pipe.

Again, note that the PVC pipe is extended out in preparation for the layers of exterior insulation, furring strips, and siding.

heat pump lines leaving house - sealed

Same area after completing the air sealing with Tescon Vana tape.

And here’s a view of the same area after the siding was installed (I’ll go into the many details regarding the installation of the exterior insulation, furring strips, and siding in a later post).

Heat pump lines w: duct seal and siding

Air sealing for the refrigerant lines complete after the siding is installed.

Additional areas where the duct seal proved to be invaluable:

close up exterior outlet box w: duct seal

Exterior electrical boxes for lights and outlets.

Conduit for the water meter in the basement (only the interior is shown below, but the conduit was air sealed with duct seal on the exterior end as well):

 

 

 

And here’s the same conduit for the water meter as it leaves the house on the first floor:

conduit for water meter sealed w: tape:gasket

Conduit for the water meter, air sealed on both sides of the Zip with the Roflex/Tescon Vana gasket.

I also had to address the disconnect boxes for our solar array and our heat pump. For instance, here’s our solar disconnect box when it’s open:

solar disconnect before removing

And here it is after removing the pull out switch, revealing an air leak:

solar disconnect before duct seal

Close up of the conduit:

close up solar disconnect before duct seal

An even closer look:

close up penetration in solar box before duct seal

And here it is after being air sealed with the duct seal:

close up solar box after duct seal

I did the same air sealing for the Mitsubishi heat pump disconnect box:

heat pump box before removing

Close up of the conduit sealed with the duct seal:

close up penetration in heat pump box w: duct seal

During my initial blower door test (more on that later), some air movement around the main panel in the basement was detected, so when the electrician came back we added duct seal to the main pipe entering the house (it had already been sealed from the exterior side with duct seal):

main panel - interior - duct seal

Close up view of the main panel from the interior where lines first enter the structure.

Besides the penetrations in the Zip sheathing, there were other penetrations through the Intello (our air barrier on the ceiling) that had to be addressed as well. These areas were air sealed with the same set of products as the Zip.

For example, in addition to the conduit for solar through the Intello, we also had to air seal conduit for electric service to the attic (for a light and switch in the attic), in addition to the the penetrations for radon and plumbing waste vents, some of which are shown below:

plumbing vent thru Intello gasket:t. vana

Plumbing waste vent going into the attic.

Another view of this vent pipe after air sealing, this time from below:

sealed plumbing vent from below

Here is one of the vents that our first, incompetent plumber installed too close to one of the 2×6’s used to establish our service core.

plumbing vent installed too close to 2x6

Installed this close to framing makes air sealing the vent needlessly complicated and frustrating.

Here’s the same area after applying the Tescon Vana tape:

plumbing vent too close to 2x6 sealed w: tape

Below is another vent pipe incorrectly installed too close to a 2×6. This one was even more challenging to air seal properly. After the gasket and Tescon Vana, I added the green HF sealant as insurance against air leaks, both for now and in the future.

vent too close w: sealant too

We also had to air seal the penetrations for our Zehnder Comfo-Air 350 ERV ventilation unit. I’ll go into the details of the actual installation later, but here are some photos of the penetrations through the Zip sheathing and how we addressed making them air tight.

ext - comfo pipe going thru zip into basement

First section of Comfo pipe going through the Zip sheathing.

 

Zehnder tube exiting w: gasket

The gray Zehnder Comfo pipe (for supply air stream) exiting the structure with a Roflex gasket.

 

Zehnder pipe sealed w: gasket and tape

Closer view of the Comfo pipe air sealed with a gasket and Tescon Vana tape.

 

close up Zehnder Comfo Pipe w: gasket and t. vana

An even closer view of this same area where pipe meets gasket and tape.

We followed the same process — Roflex gasket, Tescon Vana tape — for the exterior side of the Zehnder Comfo pipe.

ext Zehnder gasket : t. vana

Zehnder Comfo pipe installed, air sealed, and ready for commissioning.

And here’s a picture of both supply and exhaust pipes for the Zehnder.

Zehnder exhaust and supply pipes ext fully sealed

Supply pipe in the background, exhaust in the foreground. The garbage bags keep out weather and animals until after the siding is up and the final covers can be installed.

During my initial blower door test some air movement around the sump pit was detected.

sump pit air sealed

Sump pit lid sealed with duct seal, Roflex gasket with Tescon Vana, and the seam between the pit and lid sealed with Prosoco Air Dam.

The sump pump discharge pipe also needed to be air sealed on both sides of the Zip.

sump discharge pipe w: gasket and joint and seam

Sump discharge pipe sealed first with Prosoco Joint and Seam, then a Roflex gasket, before applying Tescon Vana tape around the gasket.

Some air movement around the ejector pit was also detected, so I used duct seal to try and block it.

ejector pit air sealed with duct seal

Ejector pit air sealed with duct seal.

For low voltage — in our case, a cable TV/Internet connection — we found a utility box at Lowe’s (also available at Home Depot and Amazon), and combined it with conduit to transition from the exterior to the interior. The diameter of the conduit is large enough to allow wires for other utilities/services to pass through as well, if necessary, in the future.

cable box

Cable box installed after the siding went up.

An engineer from Comcast-Xfinity visited the site back in the summer, and he gave me the go-ahead for using this box/conduit set-up.

close up exterior of closed cable box

Closer view of the cable box.

 

cable box ext without cover

The cable wire exiting the house through the conduit, which is air sealed with duct seal.

 

cable wire int. basement

Cable wire on the interior of the house exiting through the Roxul insulation and Zip sheathing via the conduit and then air sealed from the interior with duct seal.

Even the wire for the doorbell was sealed with a gasket and tape.

doorbell gasket and tape

When the weather warmed up I was able to experiment with the Prosoco R-Guard series of products (note the 3/4″ plywood door buck treated with Joint and Seam and Fast Flash). I’ll go into that more when I discuss prepping for the windows and doors later.

 

close up of doorbell gasket

A closer view of the doorbell gasket.

Air sealing the penetrations was challenging at times, but also a lot of fun — always keeping in mind the goal of meeting the Passive House standard of 0.6 ACH for our blower door test.

Convinced of the connection between air tightness and the durability of a structure — not to mention the impact air tightness has on heating and cooling loads (i.e., monthly utility bills) —I wanted to see just how air tight I could get the house.

Hopefully this inventory of penetrations will prove helpful to someone in the planning stages of their own “air tight” build. It always helps to be able to see how other people do things — in particular, the strategies they employ and the specific products they use. Seeing these real world examples of air sealing around the many penetrations in a structure will hopefully give others the confidence to come up with their own plan of attack for building an air tight structure.