Comcheck using 12" cmu with insulated cores. What to assign R-value

[Fast_Edd1e]

Im having some trouble trying to understand how to fill out my walls on comcheck in regards to a partially insulated cmu wall.

Contractor wants to use 12" cmu bearing wall and insulate the cores. No interior insulation Just 12": split face cmu. I have done this in the past for a car service bay, but prior to having to do comchecks.

So on the comcheck I select "concrete block, 12" partially grouted, cells insulated". But then it wants an R-value. Structural engineer says we will likely be grouting solid 32" o.c. vertically. Does comcheck have a place for that? Do i need to design a wall that a percentage is solid grouted and the rest is hollow with insulation? Does it know what percentage is being grouted? I wouldn't consider core insulation to be "continuous".

 

[Yankee Chronicler]

Im having some trouble trying to understand how to fill out my walls on comcheck in regards to a partially insulated cmu wall.

Contractor wants to use 12" cmu bearing wall and insulate the cores. No interior insulation Just 12": split face cmu. I have done this in the past for a car service bay, but prior to having to do comchecks.

What stage is the project at? Is the contractor the client? Have construction documents showing some other type of exterior wall construction been approved and permitted? Did you previously submit a COMcheck for some other exterior wall system?

I ask because IF this is a change to approved and permitted construction documents, the contractor in proposing the change bears ALL responsibility (and cost) for documenting that the proposed substitution complies with applicable codes and regulations, as well as bearing the cost of preparing and submitting amended construction documents to the AHJ.

 

[Joe.B]

If this is in the design phase, consider proposing ICF instead of CMU?

Advantages of block construction with better insulation and better strength. They're even some companies getting away from the classic Styrofoam:

Soundproof & Energy-Efficient Insulated Concrete Forms | Nexcem

Nexcem high-performance insulated concrete forms are a simple way to build. Each interlocking unit is fireproof, soundproof, and insulated.

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[Fast_Edd1e]

What stage is the project at? Is the contractor the client? Have construction documents showing some other type of exterior wall construction been approved and permitted? Did you previously submit a COMcheck for some other exterior wall system?

I ask because IF this is a change to approved and permitted construction documents, the contractor in proposing the change bears ALL responsibility (and cost) for documenting that the proposed substitution complies with applicable codes and regulations, as well as bearing the cost of preparing and submitting amended construction documents to the AHJ.

This is still in the design phase. Exterior finishes are approved by the township. But pricing is being a large driver for decisions.

Ive done alot of research on the insulative values of cmu based on insulation type and reinforcing required and I am not finding a way of getting the wall to work in comcheck without some form of continuous insulation. Im reaching U-values of .232 for the wall system as single wyth. And im not interested in fudging the numbers when im getting envelope fails of -4%. So i think im getting it figured out and what is being proposed just wont work.

 

[Yankee Chronicler]

Have you reached out to the NCMA for advice?

I'm inclined to agree with you. The entire concept of dropping some bits of foam into some of the cells in a CMU wall never made much sense to me. It's better than nothing ... but not much better.