We are building a new house on a slab but we are going to raise the floor about 8″ over the slab. We are going to put a rigid insulation on the slab to keep the floor warmer. I have heard that some rigid insulations will eventually liquify over time due to condensation on the slab under the insulation. If this is correct, what kind of insulation does not do this and also does not decrease in insulating value over time. I would appreciate any information that anyone out there has. Thank you.
MinnieJ
Replies
Never heard of such a thing and I've been in the commercial building design and construction industry for 27 years.
Probably your best bet is to use the pink, blue, or grey rigid polystyrene insulation. This is an extruded insulation ... as opposed to the expanded white or 'bead' board polystyrene. The pink, blue, or grey board is most commonly used for direct contact w/ earth, water, etc.
Never really heard of someone raising their floor over a slab like you are thinking. Why do the slab at all, then? seems like a big expense and you're not using it. Why not just do a crawlspace and then a framed floor? Probably a detail you didn't reveal that makes sense ... just thinking out loud.