Comments on: The Problem of Getting Air for Atmospheric Combustion Appliances

By: A. Tamasin Sterner

A. Tamasin Sterner — Sun, 15 Mar 2015 02:45:37 +0000

Thanks. Pages 440 and 450 of
Thanks. Pages 440 and 450 of NFPA 54 refer to ACH of the "space" in one section and then ACH of the house in another section. Fun.

By: A. Tamasin Sterner

A. Tamasin Sterner — Sat, 14 Mar 2015 22:45:37 +0000

Thanks. Pages 440 and 450 of
Thanks. Pages 440 and 450 of NFPA 54 refer to ACH of the "space" in one section and then ACH of the house in another section. Fun.

By: David Butler

David Butler — Thu, 12 Mar 2015 08:26:14 +0000

@Tamasin, common sense aside,
@Tamasin, common sense aside, my interpretation (NFGC Section 304.5.2) is that ACH refers to whole house since the code does not specify otherwise. Also, if it were intended to apply to CAZ, the code would have to define CAZ, which I don't believe is defined in NFGC or any other ICC code.

Ultimately, regardless of what I may believe, or anyone else for that matter, it depends on how the local inspector interprets the code.

By: David Butler

David Butler — Thu, 12 Mar 2015 04:26:14 +0000

@Tamasin, common sense aside,
@Tamasin, common sense aside, my interpretation (NFGC Section 304.5.2) is that ACH refers to whole house since the code does not specify otherwise. Also, if it were intended to apply to CAZ, the code would have to define CAZ, which I don't believe is defined in NFGC or any other ICC code.  <br />  <br />Ultimately, regardless of what I may believe, or anyone else for that matter, it depends on how the local inspector interprets the code.

By: A. Tamasin Sterner

A. Tamasin Sterner — Wed, 11 Mar 2015 17:33:31 +0000

Does anyone know if NFPA 54
Does anyone know if NFPA 54 wants us to use ACH of the whole house? Or ACH of just the CAZ? The common sense is ACH of the CAZ, and that requires a house-to-CAZ zone pressure test and calculate air leakage to the CAZ from the outdoors. Are any of you using the KAIR Method vs. the Standard Method?

By: A. Tamasin Sterner

A. Tamasin Sterner — Wed, 11 Mar 2015 13:33:31 +0000

By: David Butler

David Butler — Wed, 11 Mar 2015 09:38:16 +0000

@Tamasin, I installed an
@Tamasin, I installed an atmospheric water heater in my previous home, which I built in 1999. Because the inspector knew I was air sealing the shell (although not to today's standards), he required me to put the prescribed outside air vent in my mechanical room, even though it connected via a louvered door to an adjacent room that exceeded the volume requirement. It was a judgement call on his part. As I recall, the code at the time included a vague comment about "tight" construction with no definition as to what that meant. If the KAIR option had existed at that time, I might have paid to have a blower door test done. (I eventually did a BD test, 8 years later, just before selling the home.)

Looking back, I can't believe I actually installed an atmospheric combustion appliance in my home! And right beside the air handler. At least we had a couple of CO monitors.

For those interested in KAIR, here's the code citation. Since ACH-n cannot be measured, and there are multiple ways to convert to natural from a blower door result, the formula should reference ACH50. Given the new ACH50 requirement in the code, I'm surprised the KAIR forumulas weren't updated in the last revision.

By: David Butler

David Butler — Wed, 11 Mar 2015 05:38:16 +0000

@Tamasin, I installed an
@Tamasin, I installed an atmospheric water heater in my previous home, which I built in 1999. Because the inspector knew I was air sealing the shell (although not to today’s standards), he required me to put the prescribed outside air vent in my mechanical room, even though it connected via a louvered door to an adjacent room that exceeded the volume requirement. It was a judgement call on his part. As I recall, the code at the time included a vague comment about "tight" construction with no definition as to what that meant. If the KAIR option had existed at that time, I might have paid to have a blower door test done. (I eventually did a BD test, 8 years later, just before selling the home.)

Looking back, I can’t believe I actually installed an atmospheric combustion appliance in my home! And right beside the air handler. At least we had a couple of CO monitors.

For those interested in KAIR, here’s the code" rel="nofollow ugc">http://bit.ly/1HzdKq1">code citation. Since ACH-n cannot be measured, and there are multiple ways to convert to natural from a blower door result, the formula should reference ACH50. Given the new ACH50 requirement in the code, I’m surprised the KAIR forumulas weren’t updated in the last revision.

By: Morgan Audetat

Morgan Audetat — Tue, 10 Mar 2015 23:58:15 +0000

We will be including a blower
We will be including a blower door test in all of our remodels by year's end.

By: A. Tamasin Sterner

A. Tamasin Sterner — Tue, 10 Mar 2015 22:52:07 +0000

We're finding the Known Air
We're finding the Known Air Infiltration Rate Method (KAIR) which addresses buildings with low air infiltration can be used when the ACHn is available (from the blower door test) when the structure has less than .4 ACHn. Sometimes, this method ends up requiring less combustion air. Is anyone else using this KAIR method?