COMcheck

[Sifu]

I have an envelope COMcheck report that provides the walls, windows, doors and foundation/floor insulation. Beats code by 1%. No roof/ceiling is accounted for. So I'm curious, does COMcheck somehow assume that if there is no value input then the requirement isn't required and completely remove it in the calculation? It has been a long time since I filled one out and I don't recall any options that would negate this.

 

[steveray]

How do the other components rate vs. prescriptive?....Never run across that, but I do remember they had some good "help" stuff on the energycodes site....

 

[Sifu]

All the elements listed on the COMcheck are at or above prescriptive. The plans indicate a roof/ceiling insulation below prescriptive....which makes me ponder why they conveniently left it out of the COMcheck. I would think the COMcheck would spit out some error or notice if arguably the most important part of the envelope is left out entirely. I guess I'll go run a dummy report and see what it does. They have to fix it, this is more for my own curiosity.

 

[Sifu]

Interesting. I just ran a dummy, simple square box with the same values as the submitted COMcheck in question. I first ran it with the roof/ceiling and it was 11% better than code. I then deleted the roof/ceiling component entirely. It gave me no errors or warnings, and the building was now 15% better than code. So I guess I answered my own question. The COMcheck will act as if there is no roof/ceiling if no values are entered. Me thinks when they enter the less than prescriptive value the 1% margin they had will evaporate. I wonder how a thermal envelope is considered complete if no value is entered for the roof/ceiling. Maybe it does this as if this were the first floor in a multi-floor building with the roof/ceiling on the top floor. Seems odd that the project info wouldn't ask that this be specified.

 

[TheCommish]

you don't know what you don't know same for comcheck, the program is doing math based on inputs, if you leave windows out of the wall assembly how would it know.

Yes I agree it should have some backstops, my take ths is a code official looking at the inputs

 

[admiralArchArch]

Is COMcheck basically running the C402.1.5 Component performance alternative calculation?

 

[Mr. Inspector]

A frame homes would not have a ceiling.

 

[Yankee Chronicler]

A frame homes would not have a ceiling.

It would if the insulation is in the attic floor and the attic/truss space is uninsulated.

 

[Paul Sweet]

I think Rick 18071 is talking about A-Frame houses, which are just large steep cathedral ceilings (or sloped walls?)

 

[Yankee Chronicler]

I think Rick 18071 is talking about A-Frame houses, which are just large steep cathedral ceilings (or sloped walls?)

Yeah -- he omitted the hyphen, so I read his post as "a house of frame construction," not as "an A-frame house."

Unfortunately, neither the IBC nor the IRC defines either "wall" or "roof," so there's no way for us to determine (according to code) when a roof gets steep enough to become a wall, or when a wall gets flat enough to become a roof.