More Best Practices
More and more frequently while speaking with building professionals, reading industry literature, and viewing product marketing materials, I am struck by how passive houses are held up as the pinnacle of residential construction—something for other homes to aspire to.
This is great to see, yet there tends to be a “but” following that statement. This hesitation comes from the perception of a passive house as necessarily containing superthick walls, a complicated origami of control layers, small windows, high-carbon materials, and—as a result—additional and unnecessary costs. And all of this is for the purpose of saving the last possible few Btus of operational energy.
At my firm, Birdsmouth Design-Build in Portland, Ore., we have been building certified passive houses for almost 10 years. This type of building strikes our team as the best science-based approach to delivering high-quality and environmentally responsible buildings that our industry has come up with to date. I have seen firsthand how the passive house approach has evolved over time, and in my opinion, today there is little daylight between any high-quality home and a passive house.
When I hear the aforementioned hesitation, it occurs to me that a lot of folks are stuck in an outdated understanding of a passive house. In North America, we’re now on what I’m calling “version 3.0” of the passive house building methodology. It’s time for our industry to shake the old image and move toward this latest version.
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14 Comments
Josh,
Great article. A comprehensive and fair history. The sort of definitive account I'll keep to re-read. It's been really heartening to see Passive House evolve, when it looked for a while like the initial rigidity would lead it into a dead end.
Thanks, Malcom! Yes, the main point of the article was to hopefully get folks to snap out of the rigid, one size fits all, circa 2010's version of passive building. I'm glad to hear it may have loosened up some preconceptions.
Thanks for the informative article.
A few questions...
If you're getting the certification money back and then some through local incentive programs, I'm curious where the local incentive program funds come from?
If your last five homes have been certified to the Phius standard, and at this point it's become just building for your staff, is it still the best use of $4000 per home to continue the certification process? (Especially if the incentives are paid by local tax revenue?)
I bet Josh will be around to reply to you soon, and I'm not speaking for him, but I will share that a lot of the professionals I speak to who continue to pursue certification long after they've proven their ability to design and build such a house, believe that third-party verification is a good thing for the industry and for homeowners.
Great overview, and beautiful project examples. Josh. I'm glad that you are finding it reasonable to meet PHIUS standards in your area! The entire planet owes a debt of gratitude to the founders of PHI and PHIUS for moving the industry forward in a big way.
As the person who first blogged here about the Pretty Good House approach and as co-author of the book, I can say that it did indeed start as a reaction against the Passivhaus standards of the time. I was involved with several of them around the same time that required R-60 walls, R-100 roofs and 12 inches of foam under the slab, and a relatively small amount of glazing, in order to meet the standard in my Zone 6 climate. It was also a reaction against LEED's complexity, expense and largely nonsensical point system. But it's good to hear that PH requirements have gotten more flexible since then.
In our Pretty Good House book we made a point to say that we have come around to appreciating everything that the Passive House programs have done, and we fully support that approach. We consider PGH to be, for many, a pathway toward PH. There are definite advantages of going through the certification process and in doing your own, intensive energy modeling. The more the word gets out what Passive House is and why it's important, the better for all of us.
It's still relatively expensive, at least for a small design firm like mine. Total added costs for the last couple of projects I looked into certifying through PHIUS were in the $15K-$20K range, and that's not including the added costs for design detailing and construction. There are no incentive programs in my area. It's good to hear that your experience, in a more enlightened and wealthier state have been different. Hopefully incentive programs grow over time to make it easier to swing certification for more people.
Why exactly do the passive houses overheat in the summer? It's not as if air conditioning or heat pump cooling is against the rules... is it? With all that insulation, the house should be insulated against the exterior heat, and retain the cool temperature inside. Or was it due to windows designed for heat gain during the winter?
As a partial answer to my own question, I found this study https://www.mdpi.com/2075-5309/14/8/2501 which mentioned factors such as:
- poor ventilation (which could be solved with an ERV)
- too much insulation in the floor, making it so the house does not benefit from the natural cooling of the earth
- south facing windows in northern climates (solar heat gain), which could be solved with overhangs and/or exterior shades
- human behaviors
- waste heat from electronic devices
- the need for thermal mass. I don't fully understand the point they were making here, unless it's that thermal mass impedes heat flow better than just insulation?
I still feel like there are easy solutions to most of these problems, so I'm confused why older passive houses didn't take them into account.
I don't think the older houses had air conditioning, because highly efficient air source heat pumps weren't available or common yet, and the PHI requirements are so strict that an energy hog such as a traditional air conditioner would be hard to include in the energy budget.
I have also found that the PHI program requires (or at least strongly recommends) a cooling setpoint of 78°, typical for Europe, but at least ten degrees warmer than Americans are used to. I believe the high humidity levels we have may be a factor, but I can't recall.
Some of the early PHI projects were advertised to be heated and cooled via the ventilation system. The thinking was that the enclosures were so efficient and so optimized that they would only need tiny burps of heat or cool to remain comfortable. Again, this may have worked in central Europe with cool evenings, not too much sun and a heating dominated climate (I suppose, at least back then... ugh). The internal heat loads helped in the heating season and they could night flush in the summer. This just didn't translate well to the U.S. climate zones with different heating degree days, insolation and humidity differences. There were also almost no heat pumps available that were small enough.
The version 2.0 passive buildings when brought from central europe to certain climate zones in the U.S. were prone to overheating. Not all passive buildings overheat in all climate zones. The reason they overheat is the same reason a yeti cooler with one side made of glass and pointed at the sun would overheat-- they were too focused on solar heat gain and had too much insulation. In the central european climates, there wasn't much need for cooling, so the standard was created with the goal of optimizing heat gains. When brought to a place like Chicago where there are cold winters (that have more sunny days), but hot summers the buildings would overheat since they saw too much sun in the winter and were way overbuilt for summer-- they weren't optimized for the climate. The Phius standard endeavors to solve for this issue.
The incentives come from the Energy Trust of Oregon, which was set up in 2002 by the state to reduce the carbon impact of its energy sector. It is paid for by surcharges on utility bills. The goal is to not only reduce energy usage, but to avoid building expensive new power generation facilities, and with through that lens it has been a bargain.
We pursue certification for a number of reasons. One being quality control. As much as I would like to think our team is so well trained and efficient, we are human and have missed things on our projects that the 3rd party certifier has caught. It also holds us accountable to our clients which is a big benefit to them. They don't have to take our word for it that we are doing the best work possible.
As an aside, our team is currently undertaking our 3rd complete do-over of a roughly 10 year old building that is failing. These homes were all built using "passive house principles" that would have never made it through certification, although they were all referred to as a "passive houses" by the owners and the builders. Certification and the quality control that comes with it would have avoided these multi $100K repairs.
For us this is cheap insurance. On top of that it brings benefit to the resale value of our clients homes, supports Phius (which is doing great science-based work and research), and shows our market that we are capable of executing to this level which brings us more and more of this type of work. It is also in support of improving our industry by creating certified homes that are the pinnacle of residential best practices.
Those incentives show foresight and I don't doubt that they are a good value on the larger scale as well. And those are all excellent reasons to pursue certification. I used to offer building science consulting on an ad-hoc basis but I found the lack of understanding regarding the bigger picture was scary. I'm fortunate to mostly work with a few, well-trained builders but they aren't easy to find, and the certification process is certainly valuable insurance. I hope I didn't imply otherwise.
Bonneville Power (program name escapes me) had a program back in the 1980's to address residential efficiency and limit the need for more power generation. Oregon may have piggybacked on this in 2002. We used some of the information as a tonic when undertaking superinsulation.
Doug
Wonderful workmanship on these highly efficient homes. Beauty is certainly more than skin deep here. I attended the 2nd Annual Passive House Conference in 2007 and it was very inspirational. We toured the Smith House and all of the people inside sent the temperature zooming on a cold November day ! Keep it going Josh !!
Doug
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