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Underslab insulation in hot climates?
Last Post 24 Aug 2008 07:48 PM by BadgerBoilerMN. 1 Replies.
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kwalla101User is Offline
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24 Aug 2008 06:56 PM
What about underslab insulation in climates where the cooling days outnumber the heating days? We're building a passive house in the Central Valley of California (climate zone 9b). It will be on a slab. There will be a partial basement for storage, including wine cellar/root cellar so I will leave that uninsulated underneath. But what about the 1st floor?? It seems pretty clear that a VB of 6-10 mil poly is necessary to control moisture, but arguably the heatloss in the winter won't be so bad as to outweigh the cooling capacity of an uninsulated slab in the summer.

FYI, nights here in the summer are almost always cool enough to open the house and we'll have a whole house fan to bleed off the heat soaked up by the thermal mass in the slab and other areas. We'll have a couple of small areas with electric resistance radiant heating (bathroom floors, maybe 1-2 other small areas) for supplemental heat/comfort when getting out of the shower.

Any thoughts, suggestions and critical comments are most welcome.

Thanks all.
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24 Aug 2008 07:48 PM
As it pertains to the heat gain. It is all about time and temperature. If the ground temperature differs 90° from the indoor design temperature (as it does here in MN in January) then insulation would be a great idea. The length of the season and other factors must be weighed in to any formula for insulation to be cost effective.

Elevated floors must be insulated to drive the heat to the proper level. How much insulation depends on the heat load of the room being heated which dictates the tube spacing and design water temperature of the panel.

An un-insulated upper floor could easily over-heat your wine/root cellar and come up short when trying to satisfy the thermostat above.
MA
www.badgerboilerservice.com
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