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COMCheck: Why doesn't C.M.U. allow for the input of cavity insulation R-Value?

O

objectivesea

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Oct 9, 2013
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Boise
I'm having trouble understanding how this particular exterior wall construction should be entered into a COMCheck:I attached a copy of the COMCheck that I am working with. The building is constructed from 18' tall 8" W x 16 " L x 8" H C.M.U. light density block. I can only use furring in part of the building, which is currently reflected on the COMcheck. For the rest of the building I want to use polystyrene, but I'm not sure how this should be input into the the report. This link has some product data showing R-Values between 4.01 (for 135 lbs/c.f. blocks) and 7.74 (for 80 lbs/c.f. blocks). But the COMCheck does not allow for me to enter a cavity insulation R-Value. It only allows for a continuous insulation R-Value. What value do I enter, and where?I could be mistaken, but I think of cavity insulations as any insulation that is interrupted by structural members. Polystyrene certainly isn't continuous in the way that rigid foam board is.

View attachment 1970

comcheck.pdf

comcheck.pdf
 
Welcome to the board.

In the '09 Energy Code, I don't think they accepted the core inserts as counting towards the insulation value.

I have used pumped in foam values from the manufacturer on projects and I use the "other" option and insert my own overall R-value. I make a composite value accounting for thermal bridges (reinforced cells), insulated cells, and then any extra finishes on the inside or outside.
 
haven't use that software for awhile. Can you just adjust the CMU R-Value and justify filling the cores in the wall assembly description?
 
Ok, I see what your saying. I wonder if there is a way to convert cavity to continuous R-Value. The software may also have a default setting for R-Value depending on the wall assembly selection?
 
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