August 19th, 2019
A Tale of Two Passive House Standards
The first time I learned about the Passive House rating system, was some time in the mid-1990s. At the time it was being developed in Germany and was primarily a Western European initiative. I remember thinking that it would be seemingly impossible to apply the same standards in the U.S. and certainly unachievable in commercial construction.
Fast forward a couple of decades. We now have Passive House certification in the states, but what many don’t realize is that there are two separate standards: Passive House Institute (PHI), which is the international standard, and Passive House Institute U.S. (PHIUS). Another lesser-known includes the fact that in the U.S. you can choose to certify using either PHI or PHIUS standards, meaning—if a building is marketed as ‘Passive House’ in the U.S., it can mean different things depending on which standard was met.
The other day, I ran across this article on the Green Building website that does a nice job of comparing and explaining the differences between PHI and PHIUS. To summarize some of the high points:
- PHIUS takes into account the different climate zones in the U.S., whereas PHI has the same standards regardless of climate (it was originally built based on the climate zones in Germany);
- PHIUS also takes into account building type, setting airtightness requirements based on building size. PHI requirements are fixed regardless of whether the building is residential or commercial; and
- The fee structure is also different between the two standards.
We’ve covered some of the fundamental differences, but what’s similar between the two? According to the article I mentioned, they both:
- Insulate to a very high level;
- Eliminate thermal bridges;
- Achieve verified airtightness;
- Take advantage of passive solar heating in cold climates and seasons and avoid solar heat gain in warm climates and seasons; and
- Include a balanced ventilation design plus heat recovery where appropriate.
The View from Here
Construction methods, climate zones and building codes are different around the world and green building standards need to be flexible enough to take these variables into account. PHIUS has come a long way in making building to this standard achievable in the U.S., while still achieving similar energy savings.
And, at the end of the day, whether it’s PHI, PHIUS, LEED or Green Globes—any standard that promotes more efficient building envelopes and higher performing fenestration products is a plus for our industry.
What’s your View? Email me directly at firstname.lastname@example.org.
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I ran across PHI a few years ago when a customer in Canada was trying to bid on a project and couldn’t because the windows, which were tested to a very high level under NAFS did not have the European testing done! To me, this was plain wrong. We are not in Germany. manufacturers already spend enough money on testing and should not need to needlessly duplicate testing expenses. The sooner we get PHI out of North America, the better.