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. It seems that one of the following strategies would make the
most sense in our situation:
- uninsulated slab with perimeter insulation to the bottom of the footer (no frost line here so that's quite shallow-- 15") and
wing insulation out to 2'.
-
uninsulated slab with perimeter insulation PAST the bottom of the
footer-- say to 24"-- and then wing insulation out to 2' (seems a
little dodgy from a structural perspective to dig down lower than the
footer to insulate to 24")
- insulated 6" slab-- would lower
heat loss in the winter-- we do get SOME cold days here-- and provide a
larger heat sink 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. |