Insulate between the joists? The front entrance was initially recessed under a concrete slab front porch covered by the overhanging second floor. I have pushed the front entrance out to extend straight down from the second floor. The new entryway is six feet by six feet. The finished slab was 7″ below the finished hardwood of the former entrance so the floor level was raised using 2×8 sleepers. I have not closed anything in yet, but today is the day. I have insulated the 2×4 walls from top plate to bottom plate. The bottom plate has been sealed to the concrete slab to prevent air leaks. The ceiling is under an existing finished space, so insulation in no an issue there. What about the floor? Do I need to insulate between the joists before installing the subfloor?
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need to or want to is your choice.. in our 6000 deg. day climate ( where do you live ? ).. i'd insulate between the joists...
just to make sure your insulation is not going to wick up any moisture from the conc. slab.. i'd lay in a poly vapor barrier / capillary break..
then i'd put my subfloor on... since we blow our walls and attics with cellulose.... when i did those.. i'd drill several 1.5 " holes in each bay .. say 3.. then i'd dens-pak the joist bays from above.... the cellulose will not support vermin like ants, mice, or termites...
if you want to use foam sheets,, make sure it is foam that is treated with borates to keep the vermin out
Mike Smith Rhode Island : Design / Build / Repair / Restore
The house in in the Washington DC suburbs and we are not adding any additional HVAC to the new entrance. The vapor barrier sounds like a good idea since slab rests on top of compacted fill.