"Scientific" Conversion from CFM50 to ELA?
I've seen divide by 18 in a few places, including this site. Is there a scientific paper that defines this number?
Asked by Nick Sisler
Posted Wed, 03/20/2013 - 06:53
Posted Wed, 03/20/2013 - 06:53
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Nick,
First of all, it's important to distinguish between equivalent leak area (EqLA) and effective leak area (ELA).
Equivalent leak area (EqLA) is the area of a theoretical sharp-edged hole in the building envelope that would leak as much as all of the building’s actual holes at a pressure difference of 10 Pa. EqLA (in square inches) approximately equals cfm50 divided by 10.
Effective leak area (ELA) is the area of a theoretical hole (with rounded edges) in the building envelope that would leak as much as all of the building’s actual holes at a pressure difference of 4 Pa. ELA (in square inches) approximately equals cfm50 divided by 18.
More information: Air Leakage of US Homes by Max Sherman.
Posted Wed, 03/20/2013 - 08:02
Sifu, what is this number used for ?
I don't understand the usefullnes of the ELA number..
Posted Wed, 03/20/2013 - 15:22
Thanks, Martin I was talking about Effective Leakage Area. I was able to find a derivation in the 2009 ASHRAE Fundamentals Chapter 16, equations 41 and 42.
Jin, it's used for some infiltration simulations, such as the hourly one recommended in ASHRAE Fundamentals.
Posted Wed, 03/20/2013 - 15:31