Hi,
I am modeling a masonry building. There have been discussions about whether the insulation should go on the outside (therefore truly continuous) with an extra veneer to finish or on the inside (interrupted only by the slabs on each floor). It does not look like ASHRAE 90.1 deals with this situation very well (e.g gives much guidance). Using Appendix A, Table A3.1A gives U Values for masonry walls with continuous insulation Uninterrupted by Framing. Neither of the cases are interrupted by framing however is it fair to use the same table in both scenarios for the energy model?
Thanks
Victoria
Francesco Passerini
engineer90 thumbs up
September 4, 2014 - 3:48 am
I think that the insulation is better on the outside side for three reasons:
1. the thermal bridges are reduced
2. condensation problems inside the wall are less probable
3. you have more thermal inertia for the indoor space.
I don't know exactly how ASHRAE is considering the issue. I'm looking forward to reading other comments.
Regards
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5922 thumbs up
September 5, 2014 - 9:32 am
I agree with Francesco. Continuous insulation and thermal mass are the important considerations.
As far as Appendix A make sure you read the assumed layers that are used to derive the values in the tables. So in this case read all of A3.1 since it describes the assumptions that went into the numbers in the tables. If your situation varies you need to make reasonable adjustments to derive your U-factor.
In one scenario you have continuous insulation and the other you do not. So if the basis of the table is continuous insulation then you would need to make adjustments to the overall assembly U-factor.