Comments on: It’s the Hole – Understanding What a Blower Door Is for

By: Phillip Richardson

Phillip Richardson — Tue, 10 Aug 2010 02:55:55 +0000

I think you are right about
I think you are right about what information, and how we present that information to the homeowner is key to helping them understand what the problems are. ELR(cfm50/sfbe) is much easier to explain, and much more understandable for the homeowner and most contractors. We have to remember, we are trying to show them what they need to do to improve energy effeciency, not show them how much technical information we can generate.

By: Elaine

Elaine — Tue, 10 Aug 2010 02:11:29 +0000

You've out-geeked me, once
You've out-geeked me, once again.
Bailes, you rule.

By: Allison Bailes

Allison Bailes — Mon, 09 Aug 2010 21:26:21 +0000

Thanks for your comment, John
Thanks for your comment, John. I'm not sure it's worth combining Blower Door results with volume for ventilation, either. I'll write about that in a future article.

Regarding the various ways of characterizing the results, I prefer ELR (cfm50/sfbe). MLR is similar (above grade surface area only) and also useful. I'm not a huge fan of the leakage areas because again, you get into extrapolating a bit too far. Determining the actual size of the leakage area from the cfm50 is tricky because the size and shape of the hole comes into play. I like it for approximations, though, and often tell people that each square foot of leakage area gives you about another 1000 cfm50.

By: John Nicholas

John Nicholas — Mon, 09 Aug 2010 17:51:39 +0000

Allison, I believe you are
Allison, I believe you are correct. The only valid reason to look at volume with a blower door test is to calculate the MVR.

There are various measurements of surface leakage. Canadian EqLA @ 10 pa; LBL ElA @ 4 pa; MPLS Leakage Ratio; rule of thumb 10% of CFM@50; others

What are the practical differences and which should auditors be using to explain to HO and contractors what to look for?