“Scientific” Conversion from CFM50 to ELA?
Nick Sisler
| Posted in Energy Efficiency and Durability on
I’ve seen divide by 18 in a few places, including this site. Is there a scientific paper that defines this number?
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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.
Sifu, what is this number used for ?
I don't understand the usefullnes of the ELA number..
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.