I am trying to figure out just how leaky this is, but I am not used
to these units, so let me try to translate them into units that I and
some others on the list may be more familiar with. I assume that the "/hr"
is a mistake and should be deleted. Let's consider a 1500 sq ft
floor area house with 8 ft ceilings, with a volume of 12,000 cu ft.
And I assume we are talking about infiltration and not 50 Pa blower
door flows. Let's convert Loren's numbers to air changes per hour (ACH).
infiltration ACH = flow in cfm x 60 min/hr divided by volume in cubic ft
So
leaky house min infiltration ACH = 0.3 x 1500 x 60 / 12000 = 2.25 ACH (!!)
leaky house max infiltration ACH = 0.7 x 1500 x 60 /12000 = 5.25 ACH (!!)
Now this is EXTREMELY leaky, especially considering that
the ASHRAE 62 recommended ventilation rate is about 0.35 ACH.
And there are complaints by some that this is too leaky!
The new version of 62 has a calculation based on floor area that
recomends 5 cfm/100 sq ft = 0.05 cfm/sq ft in Loren's units.
So unless I have misinterpreted Loren's numbers, I do not think they
represent what we would call a typical range of leaky houses that we
see in the US ( my guess is 0.75 - 2.0 ACH?). Remember that the rule
of thumb is that to get infiltration ACH, you divide blower door 50 Pa ACH
by 20, so Loren's houses would test at 45 - 105 ACH50! Duct leakage
is probably the only practical (?) way to get these very high infiltration
rates, since this much shell leakage would be intolerable. In fact,
I doubt there are many houses in this range, outside of Key West.
I hope this makes sense,
...Dave Saum
Infiltec Air Leakage Control
www.infiltec.com
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