Question: Can You Use Polyiso Insulation Under Concrete?

Why do they put foam under concrete?

Concrete contractors learned that a layer of poly helps to keep a slab dry, because it stops upward vapor diffusion from the soil.

The foam layer isolates the room-temperature slab from the cold soil under the slab..

How much does Polyiso insulation cost?

The average cost of polyiso insulation is $0.70/sq ft. for a 1” thick panel. The R-Value starts at R-8 when installed, degrades down to R-5.5 over time (Cold-Weather Performance of Polyisocyanurate).

Can Polyiso be used below grade?

Polyiso has the highest R-value per inch of any rigid insulation. … However, polyiso absorbs water easily, so it can’t be used below grade. Polyiso always has a facing on both sides, most often foil.

What is the best insulation for under a concrete slab?

Applying a bead of polystyrene-compatible caulk or mastic to the top of the insulation board minimizes water infiltration behind it. For under-slab applications, the rigid foam insulation typically should be installed over a gravel base, with a poly vapor diffusion retarder between the gravel and insulation.

Where can I use Polyiso insulation?

Polyiso insulation boards are the most widely used low slope, above-deck commercial roofing insulation. As a versatile choice for commercial roofing applications, polyiso is designed to be part of any modified bitumen, built-up, or single-ply roofing system.

What is Polyiso insulation used for?

Polyisocyanurate (Polyiso) is a closed-cell, rigid foam board insulation that is bonded to facers on both sides, which are composed of various organic and inorganic materials. Polyiso is used in roof, wall, ceiling and specialty applications within commercial and residential buildings of all types.

Is Polyiso waterproof?

Polyiso. Polyiso is a rigid foam board insulation used for roofing and for insulating walls and ceilings. … This creates its closed-cell structure and makes polyiso exceptionally waterproof.

Is it worth insulating a concrete floor?

Concrete floors have a reputation for being cold, and it’s true that concrete has a lower insulating value than most other building materials. Your concrete floor is probably not the biggest source of heat loss in your home, however, and if your floor is cold, there are ways to improve its heat retention.

Is Polyiso a vapor barrier?

Polyiso provides one of the highest R-values per inch of any rigid insulation (R-6.0 at 1 inch). Furthermore, when properly installed, AP Foil-Faced Polyiso Continuous Insulation functions as a water-resistive barrier, vapor barrier and air barrier, eliminating the need to install additional components.

What does Polyiso insulation weigh?

ISO-C1/2.5 is Dyplast Products’ 2.5 lb/ft³ polyisocyanurate rigid, closed cell, foam insulation.

Why do you put plastic under a concrete slab?

The sand layer cannot dry downwards by vapor diffusion because of the plastic sheet—it is a vapor barrier after all. In fact that’s why we have it under the slab. We want a vapor barrier under the slab. ** We want to prevent water vapor from coming up from the ground into the concrete slab.

Should you put Styrofoam under concrete?

Putting styrofoam under the slab is fairly common here. If the base is preped and tamped properly, and the correct concrete and wire is used, you will crack no more or less than you would without the foam. use plastic VP under the foam, and you will end up with a nice warm dry slab, GMOD.

What happens if Polyiso gets wet?

Most rigid roof insulation, including polyiso, will remain relatively dry, even when exposed to significant amounts of water vapour. A concern may arise, however, if water vapour in ambient air contacts a surface of insulation, which is below the dew point temperature and condenses as liquid water.

What is the R value of Polyiso?

5.6 per inchThe bulletin recommended using an in-service R-value of 5.6 per inch of foam thickness. This in-service R-value was intended to account for polyisocyanurate insulation’s R-value losses over time and provides a more realistic design R-value for polyisocyanurate insulation during a roof sys- tem’s entire design life.