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Passive House in North America

Our April EBN feature article--"Passive House Arrives in North America: Could it Revolutionize the Way We Build?"--went online today. This was a fun article to research and write, because it put me in touch with my low-energy building roots. Until digging into the history of Wolfgang Feist's German Passivhaus standard, I hadn't realized that this building system really had its origins in North America--with the passive solar energy and superinsulation movements of the late 1970s (back when I got involved in this field while working in New Mexico).

Feist combined passive solar and extraordinarily well-insulated building envelopes to create buildings (both residential and commercial) so energy efficient that they can be heated using ventilation systems with small, 1,000-watt, in-duct electric heaters. Feist credits Amory Lovins of the Rocky Mountain Institute with this idea--that by investing in the building envelope, heating and cooling systems can be downsized dramatically. Energy loads are so small that buildings can be made net-zero-energy by installing rooftop PV.

Germans are known to value precision, so it is little surprise that the Passivhaus standard is highly quantitative, rigid, and performance-based. In bringing Passivhaus across the Atlantic and creating the Passive House Institute – U.S. (PHIUS), German-trained architect Katrin Klingenberg adopted the German standard exactly, retaining the 15 kWh/m2/year (4,755 Btu/ft2/yr) standard for heating, the same standard for cooling, a total primary energy consumption (including lighting, appliances, and plug loads) of 120 kWh/m2/yr (38,000 Btu/ft2/yr), and an airtightness standard of 0.6 air changes per hour at 50 pascals of pressure difference across the envelope (0.6 ACH50).

What I like about Passive House is how clear it is. The energy consumption and airtightness targets are spelled out precisely, leaving very little room for ambiguity. And those standards are really rigorous. If a house meets the Passive House standard it will be one of the most energy-efficient buildings in the country--period. As noted above, taking such buildings to the next step--making them net-zero-energy--is relatively easy.

The problem with Passive House is that same rigidity. The Passive House requirements could be tweaked, I believe, to make it work better in North America and for existing buildings. Background on these ideas is covered in the EBN article, but let me get right to a handful of specific recommendations. I'll look forward to comments about why these suggestions do (or don't) make sense, what I'm missing, what else could improve Passive House, and any other comments you might have.

  • In very cold or very hot climates, relax the heating and cooling requirements while maintaining the total primary energy consumption limit. In climates with very high heating or cooling loads, the Passive House standard right now may be too difficult to achieve. As long as the total primary energy use standard (120 kWh/m2/yr) is met, why not let more energy be used for either heating or cooling? In very cold climates, when little or none of the 15 kWh/m2/yr for cooling will be needed, why not allow some of that energy to be used for heating? And vice-versa for hot climates where little or no space heating is needed, but more energy may be needed for cooling.
  • Eliminate or minimize the bias against small houses. Because Passive House standards are based on floor area, larger houses can use more energy and meet the standard, and it's harder to certify small houses. The same holds true with the airtightness requirement, which is based on air changes per hour instead of cfm of air leakage per unit area of envelope. There is a bias in favor of large houses, even though a large house meeting the Passive House standard may use significantly more energy than a really compact house that doesn't achieve the Passive House standards. So why not tweak the standard to give a break to small houses--for example, allowing an additional 2 kWh/m2/yr for heating or cooling if the house is under a certain size, say 100 m2 (1,076 ft2)? Alternately, the standard could be pegged to the number of bedrooms rather than floor area (but that would be a more fundamental--and difficult--change).
  • Relax the Passive House standard for existing buildings. Solving our climate crisis will require a huge focus on existing buildings, and a strong standard like Passive House could be a tremendously important tool in getting there. But it's just too hard to achieve right now. I'd like to see a panel of leading energy experts who are familiar with the North American housing stock--but also committed to dramatic reductions in building energy use--put their heads together and come up with a more reasonable Passive House Retrofit Standard for North America. I'm guessing that such a group would come up with something like doubling the energy consumption limits (to 30 kWh/m2/yr for heating and the same for cooling) and raising the airtightness standard from 0.6 to to 1.5 ACH50.


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What do you think? Are these three recommendations reasonable? If not, what would you suggest? Post comments below.

Alex Wilson is the founder and executive editor of Environmental Building News. To keep up with his latest articles and musings, you can follow him on Twitter.

Photo: Dan Whitmore of Blackbird Builders used a "Larsen truss" detail in this Passive House he is building in Seattle for his family. The 14" wall cavity will be insulated with dense-pack fiberglass to achieve approximately R-55. Photo: Dan Whitmore.

Published March 31, 2010

(2010, March 31). Passive House in North America. Retrieved from

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April 13, 2010 - 12:53 pm

I,too, have a problem with the limits calculated based on square feet of building. Being a construction estimator, I know it costs more to build a house that is 1800 square feet with 10 foot ceilings than it does to build the same square footage with an 8 foot ceiling. The same holds true for heating the two buildings. We should be discussing the calculation based on the cubic footage of the building.

March 31, 2010 - 10:00 pm

What is the best approach to sell this to the consumer? I believe education is the obvious answer, and wish everyone was open to logical analysis. Can you think of any way around the resistance by homeowners to make the initial investment for design consulting and an energy audit?

April 1, 2010 - 12:04 pm

James Brew, a principal architect at Rocky Mountain Institute, has recently become a Certified Passive House Consultant, and is working on the design documentation for Amory's home (and RMI's original headquarters) to achieve Passive House certification. It's great to see it come full circle since Amory influenced many of the design principles.

April 3, 2010 - 7:46 am

"What is the best approach to sell this to the consumer?"

As long as we continue to think of creating basic shelter as "selling" a product rather than serving human need, and as long as we continue to think of the client as a "consumer" rather than a person with an authentic need, we will never get beyond the current destructive paradigm and move into a truly sustainable culture.

April 6, 2010 - 1:57 pm

An informative article indeed. I would like to know if you plan on covering other European building systems outside of the passive house niche? There are many complementary technologies being used in the thousands of buildings constructed to performance-based standards such as Swiss Minergie (14,000 buildings and counting). Here is a very good MIT study comparing green building in the U.S., Germany, and Switzerland.



April 6, 2010 - 10:37 am

I agree completely with your thoughts of energy consumption for heating or cooling being flexible/assignable depending upon the climate in which the home is constructed. As a Wisconsin based builder, we believe it must be about year-end-results. As our Company strives to reach "affordable/dependable" net zero energy consuming homes, it doesn't mean we won't use utility energy at times, but it does mean we'll balance at zero or less annually.

April 6, 2010 - 10:09 am

I don't have a problem with a high standard, and I wouldn't avocate lowering a standard just because some homes won't meet it. I say make up another standard for some other target you are trying to hit. I like that Passive House shows that this level of energy efficiency is possible.

It's also important to note that the Passive House standard is based on comfort requirements, so missing the mark has consequences for perceived comfort (and moisture issues).

April 5, 2010 - 8:47 pm

Doubling the airtightness requirement to 1.5 ACH50 would most likely be counter-productive to the entire philosophy of the Passivhaus Standard. With such loose airtightness the energy loads required to heat the home would probably be exponentially greater, undermining the entire intent of the standard.

Applying/creating from scratch a new Passivhaus standard for existing homes is an interesting idea. I'm open to see what solutions/comments others have.

April 10, 2010 - 7:04 am

Our project - the Jamaica Plain (Boston, MA) Green House - is in final stages of rehabbing an abandoned 1909 former corner store, aiming to meet the passivhaus standard and doing public education as we go. We're rebuilding the old storefront to serve as an outreach center, the rest of the space being our home (2 adults, 3 kids, ages 7, 9 & 11). Have been running a blog ( and Facebook page, done many tours and given a number of speeches. Interested to read about possible relaxed ph rehab standard. We're in good shape re: energy use, having just secured a grant from NStar enabling purchase of Altherma heat pump, but would be great if we didnt' have to get our blower door test down from 300 to 150 cfh or so.

April 7, 2010 - 1:32 pm

David, I'm curious where you're getting your numbers on the embodied energy of PV? The numbers I have seen are much lower. For example, we wrote about this study:

Which indicated that all PV technologies pay back their energy use within 3 years, with an estimated lifespan of 30 years or more. Emissions are also greatly reduced compared with other technologies.

April 7, 2010 - 1:25 pm

Thanks Alex for a great article. I have a few comments:

- PH is primarily about energy, but not exclusively. Not only is durability addressed, as mentioned in the article, but indoor air quality and comfort are also folded in. IAQ through ventilation rate calculation and comfort through window recommendations - these are based not on energy but comfort.

- Dr. Straub asked, "why harp on heating energy?" In my opinion, it is 1) the thing that building production can be the most about (hard to design a better fridge or limit the number of plasma TV's), 2) the thing that is most expensive to alter later in the process (as opposed to new appliances or mechanical equipment, or changes in behavior), and 3) the most necessary of all energy-based amenities. People can be healthy and happy (indeed more so) without TV but can be in danger without heating.

- I think that net zero is a good goal, but needs better accounting for the embodied energy of PV, because it is quite high and because PV serves no purpose other than energy generation. The PHPP uses a PE factor of 0.7 for PV (other sources vary). That is to say that 0.7 kWh of fossil fuel were used for every 1 kWh of electricity that the PV produces. The fact that that number is less than 1 means that PV could self-replicate, and be 100% renewable, albeit at great expense. But for now it is made with fossil fuel, and net zero calculations should reflect that. I recently ran some numbers and it looks like about 25% extra PV would produce enough electricity to offset, at the conventional grid, the same amount of emissions caused by the PV manufacture.

- Regarding alterations to the PH standard, i think it would help for the calculation process to be more specific to US behavior. PHPP uses a PE site to source conversion factor for electricity of 2.7 (Euro average), but in the US we have about 3.3-3.4. That is important to account for, especially as plug loads steadily rise and many of us move to all-electric buildings. PHPP also has occupants using 7 gallons of DHW a day - Americans use about 17. I often use one calculation for certification and another for design/cost analysis for this reason. Assumptions for appliance and lighting use may also need adjustment based on US behavior.

- I agree about eliminating the bias against small houses. One approach is to keep a per-area standard but set upper and lower limits on the total. This would reward smaller houses and rein in larger houses. A per-person standard would be best, and would also nicely match the physics of fresh air heating (appropriate flow rate determined mostly by occupancy), but I think is hard to enforce.

April 7, 2010 - 4:24 pm

Katrin Klingenberg says towards beginning of article that anything less tight than the current standard introduces moisture issues, which is a good argument for drawing that line in the sand. However, she later is open to loosening that standard. I actually like the idea of customizing air tightness rating according to blocks of geographical locations but not at the risk of moisture issues. It seems like she is contradicting herself and I am wondering if anyone can clarify this for me in case there is further info not in the article.