Does anyone know the origin of guarded blower door testing, and when the process was first developed?

I know it goes back to the early to mid-1980s, however I don't know when it was developed or who developed it. I'm hoping someone on here knows.


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Hi Kim,

Wikipedia has some dates and a bit of the history, not sure if it adds anything to what you already know.

What are you searching for?


Hi Bud

Information specific to guarded blower door testing. Someone asked when the process was developed and who developed it. No one seems to know.

I would look into reports from the 1980s by Sheltaire Scientific for the CMHC. Here's an example for testing procedures to use multiple blower doors to characterize attic ventilation leakage areas. Also, check out this LBNL report about uncertainty with multi BD tests, they have some background. 



Thank you for these links Brennan!

way back in late 70' doing new work we used a 30" attic fan with what is now called ECM-x13 motor 56 frame , We used cardboard to fill in holes in a window.  For testing presser we used a inclined magnehelic water type.   The whole thing was 400 lbs- took a day to set up and test.  The way we used was copy of what was done at a super insulation -solar -  PCV flued furnaces conference  Harold Orr did a class on blower door late 70 in twin city.   Some of H Orr stuff came from 50.   We tested to .5 in of water.  The math was to hard for me so then I started calculus.   so much better now  same test now is just 20 min

That same house that meet highest sealing rate in early 1980 we went back and super sealed it and went from 1130 CFM at now -50 PA now is 365 CFM with sealing better all rim and can lights, oak wood plank  entry  ect.   The point I am making is with IR and new blower doors  its sooooo much easier to test out when doing the work

Hi Kim,

Brendan Reid here, currently with Comfort Institute and Aeroseal.  Background:  I founded Retrotec in 1980-81 with Sebastian Moffat, who later started Sheltair Scientific - referred to earlier in this thread. Colin Genge came on in 1982 and really took it to where it is today.

Sebastian and I served on the original Canadian General Standards Board 149 committee on Airtightness Testing of buildings.  I think that committee formed around 1983.  

At that time, I think the concept of neutralizing pressures in adjacent units was fairly common knowledge amongst the committee members.  I am not sure if anyone in particular had the initial idea - it was a time of intense discovery.   If so, I would guess Sebastian or John Shaw with NRC.  I can't find my paper copy of the CGSB 149 standard, but if you have access you might find a reference to the concept there - at least in reference to why a single blower door (door fan) test on a building with shared walls/floors with other conditioned spaces will not give an accurate total leakage to outdoors result.

On the topic, Colin and I pioneered a variation on the approach in 1987 for the NFPA 12A standard which predicted halon gas leakage from blower door tests.  The process involved neutralizing the pressure across a suspended ceiling in order to better understand the below ceiling leakage area.  

Hope this helps, let me know if you have any other questions.  I can be reached at 360-420-5049 or

Brendan, Eric, great stuff!

Thank you for this info! This fills in some gaps. Gary Nelson recalls doing guarded blower door testing as well in the early or mid 1980s, however he wasn't sure when it was first developed.

Most likely had to do with Colin Genge of RETROTEC


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