Before we purchased our empty lot we had been told that our subdivision has a fairly high water table, so managing underground moisture, especially with a full basement, was going to be a necessity.
In order to better control water below-grade we had our concrete subcontractor install drain tile on the exterior and interior sides of the foundation walls at the footings in order to maximize the amount of water that could be quickly and efficiently sent to our sump pump. Once our sump pump ejects the water outside it travels through an underground pipe to a culvert out by the street, moving with the aid of gravity, along with water collected from our neighbors’ homes, before ending up in the municipal system.
In addition to the spray-on damproofing applied to the exterior of our foundation walls, the 5″ of Rockwool on the outside of our foundation also encourages water to make its way down to the drain tile system before it has a chance to collect and sit, causing serious problems.
At grade, around the perimeter of the house, we also decided to install a gravel border, both for its decorative effect and its ability to encourage water to move away from the top of our foundation and down to the drain tile, particularly during periods of heavy rainfall.
We also considered various ways to protect and finish the top of the exposed Rockwool on the foundation. Here’s an older Green Building Advisor article discussing the issues involved along with possible solutions (as far as I can tell there’s still no single, obvious solution yet, although a parge coat or stucco finish is arguably the most attractive and durable, especially if combined with a gravel border as opposed to just top soil): GBA
After initially deciding to go with a combination of tile backerboard and Tuff II (giving the exposed insulation the look of finished stucco or exposed concrete), we ended up using metal flashing from coil stock instead (typically available in the widest number of options from a local roofing supply company).
It was only after construction began that I learned the tile backerboard manufacturers don’t honor warranties for this below-grade application (perhaps this will change in the future, or maybe they’ll develop a product for this specific application). Although I know the product is commonly used in this way (I couldn’t find an example of a bad experience, or a case of catsastrophic failure anywhere online), the lack of warranty protection doesn’t bolster confidence for its long-term durability.
In this regard, I imagine some kind of gravel border is probably essential, especially if the house would otherwise be surrounded by a lot of clay soil that likes to retain moisture. Also, just getting the backerboard attached to the foundation through the 5″ of Rockwool would have been time consuming (assuming you can find long enough flat-head concrete screws, which we unfortunately didn’t), so we opted instead for metal flashing mainly for its ease of installation and for some cost savings.
January, 2021 Update: Another option worth exploring is using sheets of PVC, as this project in Minnesota has done with Azek’s exterior grade PVC:
Starting on the green Zip sheathing as if it was a typical Z-flashing, we had the siding guys just continue the metal flashing down the face of the Rockwool on the foundation below where we knew the level of the gravel would end up (more on this in a future blog post regarding siding installation details). So far this has worked out well, with the metal flashing avoiding damage, and without much “oil canning”, even on the west side of the house, which has the largest amount of exposure. It probably helps that the metal flashing in this area around the house is the same color as our siding, helping it to ‘disappear’ visually to some extent.
When our excavator did backfill, knowing we were going to have to cover the Rockwool around the top of the foundation, we had him hold back on the top 16″ or so. With this ‘trench’ left exposed, we first applied landscape fabric in order to try and control weeds in the future, and to better contain the washed gravel that we would be putting down inside the trench.
Setting up the landscape fabric.
As with many other areas of the house, we decided to opt for a more informal look, avoiding a perfectly consistent and squared-off border, preferring more of an undulating path as the outside edge makes its way around the house.
Section filled with gravel.
And instead of moving around endless loads of gravel with wheelbarrows, we rented a compact front loader, in our case a Ditch Witch (sometimes referred to generically as a ‘dingo’), which made the project go much faster while also saving everyone’s back.
We had watched Felipe move gravel and other materials around during the construction of our stone window wells, so we knew just how versatile and useful these machines can be — and they just look like a lot of fun to use, which they are.
We rented the machine from a Rental Max location near us, which wasn’t cheap, but we definitely felt like we got our money’s worth, as it saved us from having to endure many hours of hard labor. My wife loved using it, in part because the controls mimic those used in video games, so it was fairly intuitive for her as she quickly learned to precisely and accurately move the machine around exactly where it needed to go, including some fairly tight spots around the house.
We think the machine is worth every penny of rental cost if you have a significant amount of landscape material that needs to be moved, especially if a wheelbarrow is your only other option, or if tight spaces preclude the use of larger machines.
Luke, Jesus, and Eduardo help me shovel and rake the gravel into position as my wife drops each bucketful in place.
The boys were profoundly disappointed that they were never given a chance to operate the dingo, especially when they saw how much fun my wife was having using it.
Northwest corner of the house as the gravel border takes shape.
View of west facade as gravel is installed and we prep for boulders.
On the west side of the house we decided to add some boulders where there’s a drop-off in grade. In addition to adding some visual interest, we thought the boulders could help with surface run-off during the heaviest rainstorms.
Adding these little gravel beds helped get the boulders set securely in the hard clay soil.
We purchased the boulders locally from Lurvey. They have a nice selection of boulders and flagstones in a wide variety of styles and sizes. We would’ve chosen even larger boulders, but we were somewhat limited in this regard, having to base our selection on what we thought the dingo could safely handle.
First boulders going in.
In addition to the boulders, once mulch and plants are added to this area we shouldn’t see any erosion in the future.
Setting the larger boulders in place, and selecting and arranging cobblestones around the edge of the gravel border, while it was a lot of work it was also a lot of fun. I can see why someone like Lew French, or Dan Snow, gets so much enjoyment from their work:
And apart from their decorative function, and their ability to help prevent erosion, kids can’t help but try out their balancing skills on the boulders.
Ninja in training.
Cobblestones going in around the edge of the gravel border for added decoration and to keep the eventual mulch in the yard separated from the washed gravel border.
There will be more photos showing how the gravel border turned out in a future blog post on the installation of the siding.
With the clay soil left exposed around the house for many weeks, mother nature didn’t hesitate to fill the void with a wide variety of ‘weeds’, some quite beautiful in their own right.
With the Zehnder and the Mitsubishi systems installed, I had some time to kill waiting for the siding guys to start, and for my first blower door test to take place, so I moved on to painting my structural steel beam and the exposed concrete walls in the basement.
Apart from a couple of walls for my wife’s office that would eventually be drywalled and painted, and a decorative finish for the concrete floor, these were going to be some of the limited finished surfaces in the basement.
We’re glad we decided to leave the basement ceiling unfinished. In doing so, not only did it mean a more straightforward installation process for mechanicals, it also means if any issues develop in the future we’ll have easy access to identify and solve any problems.
I debated whether or not to spray the basement ceiling — the floor joists and the underside of the sub flooring — but decided that the color change (some shade of gray? black?) wasn’t worth the effort.
Although obviously not to everyone’s taste, we like the unfinished look of the ceiling, especially when combined with the texture of the painted concrete walls and our painted steel beam (not to mention the eventual decorative finish for our concrete floor slab — I’ll go through the details in a future blog post since it was applied much later in the build).
Steel Beam
For the beam, I first used a wire brush and some sandpaper to remove any loose and flaking rust. Using a Sherwin Williams primer, their All-Surface Primer tinted gray, I applied a heavy, uniform coat to help prevent the return of any rust in the future (keeping humidity in the basement under control should help a lot in this regard).
After wire brushing off loose rust, priming the beam in preparation for paint.
After priming, I then applied two coats of a Safecoat product, their semi-gloss in Patriot Blue.
Patriot Blue for the steel beam.
If I could do it over, I think I’d use Safecoat primers and paints for almost all of the interior surfaces. For the sake of convenience, since they have stores near me, I mainly used Benjamin Moore’s Aura Matte and Satin for walls and trim, and ended up mostly disappointed with their performance — hiding is pretty mediocre, flashing when you try to do spot touch-ups, and over-priced for the level of quality. Benjamin Moore does a great job with their marketing materials and with the look of their labels, I just wish the same level of thought and attention to detail went into the quality of their finishes.
Safecoat is available at various stores in the US, but unless you want a stock white, tinting may happen at Safecoat headquarters before shipping to individual stores, so there can be a wait involved (check with your local supplier for details).
I had good luck ordering from Green Building Supply in Iowa. After ordering online, the products are shipped directly to the job site or your home. This gives you access to high quality No or Low VOC products that, at least in my case, are otherwise currently unavailable in local hardware or paint stores.
Unfortunately, they can’t ship during cold spells, since the paint could freeze and be ruined. When it was cold and I needed product, I found Premier Paint and Wallpaper just outside of downtown Madison, Wisconsin (about a 2 hour drive for us). They’re a family-owned shop, and it shows. They have a nice selection of Safe Coat products. In fact, their wide range of products from various brands is impressive, and the people who work there are really helpful and just easy to work with. Unfortunately, I haven’t found a similar paint store in my area. Around me, Benjamin Moore (aka JC Licht), Sherwin Williams, and Pittsburgh Paint stores dominate the market. The smaller mom-and-pop stores, for the most part, don’t really exist anymore, which is a shame.
Paint going over the primer.
The Safecoat products that I’ve used typically have some odor, but what little smell they do have tends to dissipate rather quickly (this is particularly noticeable if you change back to a more conventional coating with more VOCs that may take weeks before its distinct odor finally disappears).
Finished beam.
It’s a shame that so many structural beams end up covered over, normally considered too humble, i.e., ugly, to be left alone. In keeping with our Urban Rustic design aesthetic, we think that if they’re given even just a little bit of attention and care they can prove to be a real visual asset to a space, especially in a basement if a more relaxed, informal look and feel is acceptable or even ideal.
Close-up of the painted steel I-beam.
Leaving the spine of the house exposed like this with a bold color emphasizes the job it’s actually doing, and it honors the material by making it front and center visually in the space, rather than trying to hide it away behind drywall or wood. This seems only appropriate since beams like this help keep a house standing upright.
Another view of the beam, and the recently primed concrete walls.
Painting Basement Walls
Once the beam was completed, I moved on to priming the exposed concrete walls:
Getting some help priming the concrete walls. She lasted about 15 minutes, at which point it clearly turned into work.
Paint color can be a finicky thing. After priming the concrete walls, I used a Benjamin Moore color, Jute, as the finish coat. In the basement it looks great, exactly what we were looking for: a nice, warm neutral khaki color. Upstairs, however, when I later did a test swatch on the new drywall this same color looked horrible, taking on pinkish flesh tones, so we ended up having to use a different color for most of the first floor. Testing out colors, even in relatively small areas, can save a lot of time, money, and headaches later on.
Concrete walls after paint.
It was really important to me that the basement foundation walls be left exposed, with no insulation or drywall.
I wanted all of the texture, imperfections, and overall character of the exposed concrete to be vividly on display. Arguably, once painted, these imperfections become even more pronounced:
There are a couple of areas of ‘honeycombing’ around one basement window. Under the right lighting, it creates a nice visual effect.
Areas with exposed conduit were also painted.
With a good chunk of the basement complete, it was time to move outside and get some work done before the siding began, and before we had our first blower door test performed…
Wall Art
It took quite awhile before we could return to the basement and get some artwork on the walls. After we moved in and got some other projects completed, we started using a plywood-epoxy combination instead of a more traditional frame and glass for a series of poster art pieces.
This involves creating a base out of 1/2″ or 3/4″ plywood. Once sanded smooth, we apply the photo to the plywood with some spray adhesive. When completely dry, we then do a flood coat of epoxy over the entire surface of the artwork-plywood ‘frame’ (typically the plywood is on a base of either 1×4’s or 2×4’s, depending on the look we want, adding stability to the frame while also making it easy to hang on a wall).
If a high gloss finish isn’t ideal, after waiting a couple of days to ensure the epoxy is fully cured, I sand it smooth, up to 360 grit with an orbital sander.
Once the epoxy has been dulled, I then apply a couple coats of hard wax oil finish like Osmo Polyx. Typically I use a satin finish, but a matte can also produce a subtle, high-quality finish. For more info, go here: Urban Rustic: Main Bedroom and Bathroom
One of the more challenging pieces began with an iconic image of the 19th century French artist, Camille Claudel. I’ve always loved this image of the young artist; to me it’s full of life, defiance, and pride:
My introduction to her life and work was through the almost operatic biopic from 1989:
The biography by Odile Ayral-Clause is also well worth a read; less melodramatic than the movie, but a much more fully fleshed out depiction of her life.
Using this image as a centerpiece, I needed a series of images to complete a collage. Using the DIY artwork from the Riot Grrrl movement collected in the pages of The Riot Grrrl Collection by Lisa Darms seemed to match the power and spirit of the artist’s life:
After getting over the uneasiness of tearing apart the pages of a beautiful book, I set about coming up with a layout for the artwork in combination with the photo of Claudel.
The intent was to surround her with the work from these various Riot Grrrl zines, hopefully making for a visually striking collage:
Series of images from the layout and post-epoxy stages:
Claudel and the Riot Grrls in place above my wife’s office desk:
An overview of the wall art in our basement:
By keeping the high gloss finish on most of the Shakespeare posters, along with the Claudel-Riot Grrrl collage, the images can do double duty with their mirror-like finish, offering objective and subjective perspectives simultaneously, pulling in the viewer while subtly suggesting no one is above the ‘Sturm und Drang‘.
The plan for our house was to combine an HRV or an ERV (for a continuous supply of fresh air), with a ductless mini split air source heat pump system for our ventilation, heating, and air conditioning needs. Almost all of the projects I had read about utilized this same combination, especially here in the US.
The only real debate, apart from specific brand options, was whether or not to utilize only one distribution head on our main floor, as opposed to installing multiple heads for a more ‘dialed-in’ level of comfort (e.g. in the basement or the bedrooms).
Our original builderhad in our construction drawings one head in the kitchen/family room and one in the basement, which was pretty standard for a Passive House level project. It was, therefore, pretty shocking to find out that our second builder (there were two partners) and their HVAC subcontractor were suggesting a system that was grossly oversized for our needs. You can read about the details here: GBA: Oversized System
This was just one of many ‘red flags’ that convinced us to move on and GC the project ourselves. It’s also a reminder that old habits die hard, meaning even seasoned contractors, in any trade, need to be willing to learn new ideas and techniques if they want to truly be considered professionals and craftsmen — unfortunately, they’re the exception to the rule, at least in our experience.
One of the disappointments associated with our build is, in fact, the disinterest (in some cases even outright hectoring contempt) shown by various tradespeople in our area for ‘green’ building generally. Doubtless, at least a partial explanation for why much of the Midwest seems so far behind in adopting ‘green’ building techniques, especially when it comes to air sealing, insulation, and IAQ beyond code minimum standards. Hopefully this changes significantly in the coming years.
Consequently, I took Steve Knapp’s advice (from the comments section of my question) and contacted Home Energy Partners (their new name: HVAC Design Pros). Isaac responded quickly and eventually did our Manual J, confirming we needed a much smaller system, one that is more consistent with a Passive House project, or even just a high-performance build more generally.
Once we were on our own, in addition to going with a Zehnder ERV and a Mitsubishi ductless mini split air-source heat pump system, we also pursued the possibility of using a Sanden heat pump water heater.
After seeing it used on a Hammer and Hand project, we thought it was a really interesting piece of cutting edge technology:
Unfortunately, after getting a quote from Greg of Sutor Heating and Cooling, and a poor response from Sanden regarding questions we had about the system (they were unresponsive to emails), we decided to stick with our Zehnder, the Mitsubishi heat pump, and then go with a Rheem heat pump water heater (going with the Rheem saved us just over $6,000 in initial cost). Hopefully, as it becomes more popular in the US, the Sanden can come down significantly in price, or maybe less expensive copycat products will someday show up on the market.
Greg was initially willing to work with us, even though we were technically out of his service area, when the Sanden was involved, but once it was only a ductless mini split he suggested we find a Mitsubishi Diamond installer closer to us, which we understood. He was nothing but professional, taking the time to answer any number of technical questions and offering what proved to be sage advice regarding various details for our system.
In fact, taking Greg’s advice, we contacted a Diamond installer close to us, but unfortunately the first installer we contacted disappeared when we were trying to get him to communicate with our electrician on installation details (an infuriating and painfully common experience when trying to build a new house — especially one with unconventional Passive House details).
Finding our Installer
At this point, we were lucky to find Mike from Compass Heating and Air. He came out to the job site and we walked through the details together. He proved to be knowledgeable, helpful, detail-oriented, and extremely professional. Installing our Mitsubishi ductless mini split system with Mike proved to be one of the easiest portions of our build. We never felt like we had to look over his shoulder, making sure he got details right, or that we had to constantly confirm that he did what he said he was going to do — in fact, it was the opposite: ‘Mike’s on site, so that’s one less thing I have to worry about’.
Mike and his crew at the job site to install our Mitsubishi ductless mini split system for heating and air conditioning.
Mike also confirmed what Greg and Isaac also pointed out: comfort issues may develop if we tried to get by with just one distribution head on the main floor.
In fact, looking back through old emails, Greg was nice enough to walk me through some of the options employed by those trying to get by with a single head for an entire floor (sometimes even two floors), including leaving bedroom doors open throughout the day (ideally, even at night), and even the use of Tjernlund room-to-room ventilators.
Again, to his credit, Greg tried to stress how important it was that homeowners have realistic expectations regarding the overall effectiveness of these techniques and options.
He also was at pains to make clear how the work of any competent HVAC installer can be easily undermined by a structure that underperforms. In other words, they can design an appropriately sized HVAC system for a Passive House, but if shortcuts occur during the build and the final blower door number comes in higher than expected, or the budget for insulation gets cut (reducing R-values in the structure), then the system they designed has little chance of working as intended. Based on what he wrote, I’m guessing he has dealt with exactly this outcome in the real world — not fun for him, or the homeowners to be sure.
Consequently, by the time Mike from Compass Heating and Air got involved, we had pretty much already settled on using multiple heads. Although it was nice to hear the same consistent message from Greg, Isaac, and Mike in this regard.
In the end, we decided to delete the head in the basement, instead going with three separate heads on the main floor — the largest in the kitchen/family room, and then the other two would go in our bedrooms.
Master bedroom Mitsubishi head and Zehnder supply, both covered to protect against construction debris.
Having the Zehnder supply diffusers on the same wall and near the head of the Mitsubishi has been working well for us. As far as we can tell, there are no discernible issues with this arrangement. By way of comparison, the Mitsubishi head and Zehnder supply diffuser are on separate walls in my daughter’s bedroom — in effect, they’re pushing air towards the center of the room from walls that are perpendicular to one another — but we still can’t tell any difference in terms of performance, either when heating or cooling.
Facing camera: Family room Zehnder supply diffuser with Mitsubishi head. To far left, and facing MBR: Zehnder supply and lines for MBR Mitsubishi head.
Mike was also really good about communicating the system’s requirements to our electrician and our plumber. It was nice to watch all of them walk through the details together, thereby ensuring there were no problems once it came time to start up the individual heads.
Components for setting up a ductless mini split: refrigerant lines, electric supply, and a drain for condensate.
Living with a Ductless Mini Split
Having lived with the HVAC system, both the heat pump and ERV, for about a year now, our only real complaint is summer humidity, which I discussed in a previous post here: HVAC (1 of 2): Zehnder ERV
This summer we’re going to try using a dedicated, whole-house dehumidifier, which we think should resolve the issue.
Otherwise, our system has been trouble-free.
In winter, the heads do make some noise, tending to ‘crack’ or ‘pop’, especially when first turning on, or when they come out of defrost mode. Although I’ve read complaints about this online, it’s never really bothered us. I remember how loud our conventional gas-fired furnace was in our last house, especially when it first turned on, so I think it’s important to remember the level of certain sounds in their appropriate context.
Also, this ‘crack’ or ‘pop’ sound is, I suspect, louder than it otherwise would be, say in a conventionally built home, since Passive Houses are known to be significantly quieter because of all the air sealing and, in particular, all of the insulation surrounding the structure.
There’s also a noticeable humming sound when the compressor is going through a defrost cycle (especially noticeable at night when the house is otherwise quiet). The heads also temporarily send out cooler air during this defrost cycle, but the cycle is short enough that it hasn’t posed any real comfort issue for us.
Setting up the compressor outside.
Regarding interior noise generally, the same holds true even for our refrigerator in the kitchen. We virtually never noticed the fridge in our last house when it was cycling, but in our Passive House it’s arguably the loudest, most consistent noise in the house, especially at night, or if quietly sitting and reading. Again, it took some getting used to, but not really that big of a deal.
In other words, having blocked out, or at least muffled, most of the noise from outdoors (due to extensive air sealing and extensive insulation), any noise indoors becomes much more noticeable and pronounced. The Rockwool we installed between bedrooms-bathrooms, and the kitchen-utility room for sound attenuation definitely helps in this regard (more on this in a later post).
Line set for the heat pump system exiting the structure after being air sealed.
Just how quiet is a Passive House? Well, one example would be the train tracks that are just a couple of blocks away: When the windows are closed the noise from a passing train is mostly cancelled out — as opposed to when the windows are open, and the train, in contrast, sounds like it’s thundering through our next door neighbor’s yard.
Interior view of the line set exiting the house.
As far as extreme cold outdoor temperatures are concerned, the system experienced a real test with our recentPolar Vortex weather. Mike was nice enough to check in with us the day before it started just to remind me that the system could shut down if temperatures fell below -18° F, which is what our local weather forecast was predicting.
In fact, this proved entirely accurate. As temperatures eventually fell to -24° F overnight, the system was, in fact, off for a few hours (the Mitsubishi shuts off to protect itself).
With the Zehnder ERV already set to LOW, and using just a couple of small space heaters (one in each bedroom — roughly equivalent to running 2 hair dryers simultaneously), it was easy to get the interior temperatures back up to 68-70° F in less than an hour (from a measured low of 61° F when we first woke up), at which point we turned off the space heaters.
And it was just under 2 hours before the temperatures rose enough outdoors for the heat pump to turn back on. On the second day, the system again turned off, but the interruption was even shorter this time, so we didn’t even bother to turn on the space heaters.
On both days the sun was shining, which definitely helped as light poured in through our south-facing windows, mainly in the kitchen and family room. Even with no additional heat, either from the heat pump or the two small space heaters, the kitchen remained a comfortable 70° F throughout that first day, regardless of the temperature outside.
In the summer, when we have the AC running, we just set the desired temperature on the remotes and largely forget about the system. The three heads together, even in each individual space, have no problem keeping the house and individual rooms cool enough. In this case, it no doubt helps that we have a substantial overhang on the southern portion of our roof, mostly denying the sun an entry point into the home during the hottest days of the year (and the Suntuitive glass on our west-facing windows takes care of afternoon summer sun).
Conduit for the heat pump exiting the house and air sealed with Roflex/Tescon Vana tape and gasket.
You can see more detailed info regarding air sealing penetrations through the Zip sheathing here: WRB: Zip Sheathing
Clean, neat lines for the heat pump.
Single or Multiple Heads?
As far as using a single head to try and heat and cool the entire first floor, in our case about 1500 sq. ft., I can only say that I’m glad we chose to use multiple heads. This really hit home as I was completing interior finishes. For instance, there were times when only the head in the family room/kitchen area was running. When you walked into the bedrooms you could definitely feel the temperature difference since those heads had been turned off (roughly a 5-10° difference). As Greg, Isaac, and Mike — to their credit — were all quick to point out, for some homeowners this temperature swing would be acceptable, even something that could be calmly ignored, while for other homeowners it might well be a heartbreaking and deeply frustrating realization.
Depending on how sensitive someone is to these temperature differences, it could prove a devastating disappointment if the homeowner is expecting uniform consistency throughout their home. Also, since much of the selling point of Passive House techniques is, in the end, occupant comfort, and not just reduced energy consumption, moving from a comfortable kitchen, for example, to a bedroom that some would find outright chilly, might induce some homeowners to ponder: ‘What was the point of all that air sealing and insulation if I’m still cold in the wintertime and hot in the summer?’ If they hadn’t been warned beforehand, like we were, it would be difficult to argue with their reasoning.
Obviously it’s only our opinion, but if it’s at all possible to fit it into the budget, by all means utilize more than one distribution head. Even if you yourself never feel compelled to turn on any of the other heads in a multi-zone system, a spouse, one of your kids, or a guest probably will want to have the option at some point.
Zehnder ComfoTubes and various lines for the heat pump as they enter the basement from the MBR and the family room.
In addition, I would also guess that when going to sell the house multiple heads would be significantly easier to sell to a potential buyer (who wouldn’t appreciate customized HVAC in specific rooms?) rather than trying to prove that a single head is sufficient for an entire home, no matter how small or well-designed. Thoughts worth considering before committing to a specific HVAC system.
Compressor with finished charred siding and decorative gravel-cobblestone border.
Also worth noting, utilizing the Q&A section of the Green Building Advisor website is an excellent resource for exploring options before committing to a final HVAC set-up. It’s an excellent way to hear from designers and builders who have experience with multiple ‘green’ projects, not to mention actual homeowners who live in high-performance homes and experience these HVAC systems in the real world, as opposed to just data points put into a proposed energy model (incorrect inputs, along with actual occupant behavior are just two ways a potential system could end up being profoundly inappropriate).
This kind of feedback — before construction begins — is undeniably priceless. In fact, I regret not asking more questions on GBA as they came up during the design and construction phases of our build since it is such a valuable resource of useful information.
View of the same area after our recent Polar Vortex (snowfall, then below-zero temps).
The one real risk we took with our HVAC set-up was foregoing any direct conditioning in the basement, either heat or AC. In the summer, no matter how high the temperatures outdoors, the basement stays within 5 degrees of the upstairs temperatures and humidity, so no comfort issues in this regard have presented themselves. In the winter, however, the temperature remains in the 59-61° range, with almost identical humidity readings as the main floor.
Some ice build-up, but almost all of it on the concrete pad below, not on the compressor itself.
Most of the time this isn’t a problem for us, since we’re either working out (the slight chill gets you moving and keeps you moving), or else we’re doing arts and crafts projects, or reading on a couch under a blanket. The only time the chill gets annoying is when sitting at the computer for an extended period of time, so we may try using a plug-in space heater in the office next winter (although the challenge will be to find one that’s reasonably energy-efficient while also remaining effective).
Close-up, showing very little ice present on the compressor itself.
For us, they’ve never been a problem. Much like the Suntuitive glass on our west-facing windows, or even a dark or bright color on an interior accent wall, after a few days, like anything else, you just get used to it. I never found them to be ugly in the first place though.
I also grew up with hydronic metal baseboards for heat, while in apartments and our first home we had the typical floor supply and wall return grilles for a gas furnace — point being, the details of any HVAC system are never completely absent from any living space. There’s always something that shows up visually and, typically, that needs to be cleaned at some point.
In addition, the Zehnder ERV and the Mitsubishi heat pumps meant we didn’t have to utilize any framed soffits or duct chases (at least in the case of our specific floor plan) in order to hide bulky runs of traditional metal ductwork, typical in most homes when using a normal furnace. Unless designed with great care, these tend to be obtrusive, taking up premium ceiling, wall, or floor space. And if randomly placed simply for the convenience of the HVAC contractor, they can be downright ugly.
In other words, it doesn’t really matter if you’re building conventionally or if you’re building a Passive House, all the details of an HVAC system — whether it’s individual components, or even how these components will be placed inside a structure — should be carefully thought through (again, ideally before construction begins) to address any performance or aesthetic concerns.
Controlling and Adjusting the System
As far as the remote controls for the individual heads, we haven’t had any issues.
For the most part, we set them to either heat or AC (roughly 70° and 75° respectively), and then forget about them.
To the extent I’ve looked through the manual, these seem straightforward, but again we haven’t really needed to do much in this regard. And when the weather is pleasant outdoors, we take every opportunity to turn off the system completely and then open windows.
Mike also explained the system could be combined with a Kumo cloud set-up, but we’ve been happy with just the hand-held remotes so far.
Routine Maintenance
And much like with the Zehnder ERV, I try to check the filters for the individual heads at least once a month (more like once a week when I was still doing interior finishes). Just as it takes much longer for the Zehnder filters to get dirty now that construction is over, the same has proven true for the blue filters in the Mitsubishi heads. It seems like about once a month is sufficient to keep up with the dust in the house.
Overall, we’ve been very happy with our HVAC set-up, including the Zehnder ERV and our Mitsubishi ductless mini split. As long as the units don’t have any durability issues, we should be happy with these systems for many years to come.
kimchi & kraut 
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