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Understanding the Energy Star Certification Report

jwolfe1 | Posted in Energy Efficiency and Durability on


I can’t seem to get Energy Star or the company that rated my house in 2016 to respond to me after several attempts. An internet search is not uncovering anything.

What does Htg and Clg represent in an Energy Star report on the air infiltration test? Does Htg stand for heating and Clg stand for ceiling? Should the 908 for Htg and 908 for Clg be added together to get the total air leakage in CFM? I have no heating/ac ducts outside of the thermal envelope except for the intake and exhaust vents.

The total cubic volume of the house is 33041 cubic feet and I am trying to figure out the ACH.

Do I take (908 Htg CFM +908 Clg CFM)*60/33041 house cubic feet = 3.29 ACH?

Or do I just use the Clg 908 number to get;
(908*60)/33041=1.65 ACH?

Does anybody know?

BTW: a HERS score of 31 seems pretty good for a production builder.


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  1. user-2310254 | | #1

    I'll give your post a bump.

  2. dennisgray | | #2

    I believe in that context the Htg is referring to air leakage during heating season and Clg to air leakage during cooling season. If a blower door test these values are always equal as far as I know. Not sure why two values, but don't add them together. Just use the 908 CFM number for your calculation of ACH50. The 1.65 ACH50 is a very good result, and HERS 31 is fantastic.

    1. jwolfe1 | | #3

      Ahhhh got it. Thank you! 1.65 great!

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