A Builder in Michigan was using Rescheck to demonstrate 2009 IECC energy code compliance as part of the permit application process.  I was consulted, because the home could not pass code through ResCheck with open-cell foam in wall cavities and foundation walls, high efficiency furnace, attic with flash coat of foam, covered with R-50 blown cellulose.

I was told by the person completing the ResCheck model, that we must now use the r-value rating of fiberglass for the cavity insulation, no matter what the rated R-value of the insulation used in the cavity.

Has anyone else heard of this illogical standard?

I have used RemRate to determine code compliance and have not used this standard.  Are there other issues like this I should be aware of?

My reading of the code indicates that the code official can determine what is an acceptable energy modeling software.

Any other suggestions for easily documenting code compliance for this builder?  I'd love to do a HERS rating for every house, but I can't believe that's necessary here.   Rescheck does not account for infiltration.  This contractor builds a tight house, I'm sure that would help it pass through the performance path.

And yes, if r-5 continuous insulation was applied to the exterior, it would pass.  I prefer that method of construction too, but that is not my question today.

 

 

 

 

 

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John

The 2009 Michigan Uniform Energy Code follows closely with the 2009 IECC.  Section 402.1.4 Total UA alternative addresses the method that RES Check follows.  The values used for assemblies can be derived from the ASHRAE Handbook. In the Handbook is a list of insulating materials each with its own U value listed as tested by a ASTM test standard, typically C 518.  For RES Check you use what ever tested R-Value is listed for the material used at its installed thickness.

Use the R-value rating of fiberglass...standard , blown or high density????

Insulation R-Values

Checklist Requirement ID: IN13

Code Section(s): 303.1

Insulation R-values. All insulation installed in the building thermal envelope should have a label on the insulation indicating the R-value of the insulation or the insulation installer has provided a certificate verifying the type of insulation, the installed thickness and installed R-value.  For blown in insulation, a certificate must provide the installed density, coverage and number of bags of insulation.   This is per ResCheck

Thanks Todd and Bob,

I've tracked down the misunderstanding on the assigned R-values. 

The next challenge is to find appropriate modeling software to see if the house passes code by its performance when air infiltration and insulation below the slab are considered.

 

John

 

You can use either DOE-2, Energy Gauge, REM Design or REM Rate.

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