Just an observation, anybody noticed that in a set of 8 BDT data points, if you simply change the “Outside Temperature” from winter to summer (e.g. 3F to 80F), the ACH increases? I re-opened some past h2k’s, played with the "Outside Temperature" and I have observed ACH increase ranges between 5-10%, using the same data points.

Because of this, a homeowner who had D evaluation done on winter (e.g. at 3F) and then E evaluation done on summer (e.g. at 80F) would have a “handicap” and not meet the full air-sealing rebate. 

Stan Jang wrote:

Hi Norman, if you tested a house in the winter and collected 8 data points to yield a particular result, that identical house in the summer would get a different set of 8 data points but would theoretically get the same result once the temperature was entered.

In other words, the temperatures (or perhaps its just the relative temperatures between the inside and outside) affect the raw data that is collected and is adjusted with the temperatures entered.

Stan

Thank you Stan. Another observation from my "desk experiments" is that when I enter different set of summer data points with lower BDT values (because the homeowner did air-sealing) and summer outside temperature, the ACH goes up, making the home ineligible for air-sealing rebates. The summer E BDT values would have to be much much much lower than the winter D BDT's to get the air-sealing rebates. 

You will note that in the latest ERS Documentation (ERS 15.12) they are tightening the protocols on Blower Door Testing using CAN/CGSB-149.10-2019 (vs the older -M86). From Section 7.4 : "Based on this Standard, the EnerGuide Rating System requires a depressurization test with the as-operated, unguarded, multi-point method with 10-second time averaging to more accurately mimic the normal operating conditions of the house during the heating season and provide repeatable results."

Make note of the "TIP" text box in section 7.6 of the Tech Procedures:

"The test procedures in place prior to version 15.12 of the EnerGuide Rating System, described here as an optimal test, meet the new CAN/CGSB-149.10-2019 Standard EXCEPT that data points cannot be dropped, the lowest pressure for the -50 Pa target is now -45 Pa, and the only parameters required to demonstrate a valid test are the n and r values."

The fact that you can't "drop" data points is interesting.  They also say that there must be no fewer than 6 pressure readings... I think before we used 5.  The one advantage is that they no longer require the < 7% Relative Error.  

Finally... yes, temps make a significant difference.  I have seen too many people just estimate or use the last value they saw on the dash of their vehicle...