CONFIRM LONG-TERM THERMAL PERFORMANCE Two of the rigid foam insulations most commonly used below grade and under slabs are expanded polystyrene (EPS) and extruded polystyrene (XPS). Although both are closed cell insulations, they perform very differently over the long term. Regarding this, what type of insulation goes under concrete slab?
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. Additional insulation is applied along the edges of the slab, because that is a primary surface for heat loss.
Also, 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.
Similarly one may ask, 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. Finally, some contractors in cold climates began installing a continuous horizontal layer of rigid foam insulation under their concrete slabs.
Should you put plastic under concrete?
Recently, though, research has shown that the old traditional layer of 6-mil Visqueen (polyethylene plastic) under the slab is seldom effective for two main reasons: Although it may seem water-tight, this grade of material allows a lot of water vapor to pass through.
Related Question Answers
Should you put a vapor barrier under concrete slabs?
A concrete vapor barrier is any material that prevents moisture from entering a concrete slab. Vapor barriers are used because while fresh concrete is poured wet, it's not supposed to stay that way. It needs to dry and then stay dry to avoid flooring problems. This is why a vapor barrier under concrete is essential. Do I need insulation under a concrete floor?
For solid concrete floors, make sure that if they need to be replaced, your builder puts in insulation – you have to insulate a floor when it is replaced in order to comply with building regulations. Solid floors are insulated using rigid insulation foam, which can be fitted either above or below the concrete. Should I insulate under garage slab?
“Energy code around here requires R-10 under the slab unless the building is unheated,” he says. “You are correct in pointing out that the foundation walls should be insulated as well. “Generally speaking, however, the only place underslab insulation is required is when the slab itself is heated. Can you insulate a concrete slab?
There are two ways to handle insulating concrete floors. You can attach wood sleepers to the floor, fill the gaps with rigid-foam insulation, and then apply your finish flooring. Or, as demonstrated here, you can cover the slab with rigid-foam insulation, add two layers of plywood, and then add the finish flooring. How much does it cost to insulate under a concrete floor?
A 50mm thick layer of proprietary floor slab insulation is usually enough to reach and maintain the target U value but this should be checked with an architect first. Insulation sheets should be laid tightly together with the joints staggered to avoid movement. Can you use Polyiso insulation under concrete?
use polyiso under a slab, or between a foundation-wall and soil. But it's OK to use on the interior side of open basements. How thick should concrete floor insulation be?
Standard thickness available are 25, 30, 40, 50, 60, 75, 100, and 150mm. Other thicknesses are available to order in 5mm increments up to 600mm. A damp proof membrane is required and should be placed over the insulation to prevent water and fine particles from the concrete leaching down the joints in the insulation. What kind of insulation should I use under concrete floor?
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. Additional insulation is applied along the edges of the slab, because that is a primary surface for heat loss. Should you put Visqueen under concrete?
If you have a concrete floor that's in continuous contact with a source of moisture, you're going to have problems. This is why a vapor barrier under concrete is essential. Vapor barriers are a way to keep moisture from getting into the concrete. Note: A vapor barrier is not the same as an underlayment. Do you have to put gravel under concrete?
Whether you pour concrete for a walkway or patio, a strong gravel base is required to prevent the concrete from cracking and shifting. Gravel allows water to drain into the ground below. When packed tightly, however, the gravel doesn't shift beneath the concrete. How thick should a garage slab be?
four-inches
How thick does a concrete floor need to be?
4 inches
What is the most common slab footing?
Footings - Concrete slabs The stiffened raft slab is the simplest and most common slab construction available. Is under slab insulation necessary?
Insulation requirements Builders with a bigger budget, especially those in cold climates, should consider installing continuous horizontal insulation under the entire slab. Slabs that include embedded hydronic tubing for radiant heat always need a continuous layer of horizontal insulation under the entire slab. Will Great Stuff foam lift concrete?
Foam that reacts slowly is great for filling voids, but not for raising concrete. Once this occurs, the only way to regain control over the slab is to cut through the layer of foam and attempt another lift again. What is the R value of concrete slab?
A reasonable R-value for a normal concrete slab can be estimated using an R-value, the thermal resistance per inch of thickness, between 0.1 and 0.2 and multiplying it times the slab thickness. For a 6-inch slab, R-value would be between 0.6 and 1.2. 
