Is rigid foam necessary under concrete slab in Central Virginia?
rikard5150
| Posted in Energy, Heating & Insulation on
We are having a house built in Central Virginia. The builder uses a CMU stem wall and then pours a concrete slab. They isolate the slab from the stem wall with 1″ XPS for R-5. This is all that the building authority requires. My question is it worth the extra cost to have the builder install R-5 on the entire stem wall and then 2″ XPS or EPS under the slab for R-10?
Thanks
Richard
Replies
I would insulate the entire stem wall and 4' in from edge of slab with rigid XPS. If you plan on any type of radiant heat integrateted into this floor, then I recommend insulating over the entire slab gravel subgrade with closed cell spray foam about 3-4" thick. If you're spraying foam, then keep in mind that your subgrade should be fully compacted, dry, and above freezing.
Thanks, that is what I was thinking.