I’ve been “looking under the hood” of the PHPP lately and seeing just how complex it is. It is why Passive House is such a good protocol – quite a bit went into developing the PHPP so that it accurately measures how a building is expected to perform once it is built. When you hear about the requirements a building must meet in order to be certified a Passive House it means that on many levels the building measures up. Even the blower door test, the thing that seems black and white – you either pass it or you don’t, has quite a bit of expected performance behind the test to assure the accuracy of the results so that the buildings anticipated performance is modeled correctly.
I came across a newly published document entitled “Guidelines for Blower Door Testing of Passive Houses” written by Gavin Ó Sé, GreenBuild, Inch, Gorey, Co. Wexford, Ireland. Gavin wrote this document because there are differences in opinion within the Passive House community of exactly what it means to perform a blower door test. He is aware of different countries interpreting the international standards slightly differently and this can lead to variances in the results. Even within Germany, the determination of what constitutes the proper method of blower door testing varies from what PHI has stated as the method it considers appropriate.
Gavin’s paper goes into detail of what areas are to be included as the building volume in a Passive House project and even provides a nicely color coded image to show what those areas are. He describes the European Norm EN13829 standard for blower door testing and how that methodology is performed with blower door testing. He is very careful to point out that his paper is not to replace the standard, but to start a discussion for expanding the standard to include specifics for Passive House that would then be understood and comparable anywhere in the world by either one of the following options (or other idea):
“a) [PHI] describe a test protocol in its entirety so that everyone follow the same procedure across the world, or
b) allow in the PHPP calculations some kind of discrepancy amount in blower test results, to allow for the fact that tests may be 5-10-maybe even 15% different across jurisdictions and even within jurisdictions, depending on how the testers understand the EN13829 regulation and the Passive house internal volume calculation” 
Because the Passive House standard relies so heavily on the detailed measurements of a project to track its energy usage and heat transfer potential the accuracy of its information and the way that information is determined must also be treated with the same care and consistency. Having a detailed understanding of how the blower door test is performed, and having that understanding throughout the world as a defined standard will benefit the Passive House movement as regulatory agencies begin to interact with Passive House projects and start refining their own energy standards.
As Gavin points out, this paper authored by him and offered by Greenbuild is presented as a “starting point for discussion”.  As the Passive House community expands and more people are building to the standard, having discussions about the specifics to rely on in testing and in performance will help define the standard in a way that is replicable across the board. Join the discussion – check out Gavin’s paper at the link below. Having well defined understandings between the people designing, building, and testing the Passive House buildings is just as important as having the accurate ways within the PHPP to measure the predicted performance before the building is built. It is the understanding of those creating (and using) the building that will translate the PHPP into the most accurate real world interpretation possible and that is something we could all agree on.