Depth Insulation Under Concrete Floor

Below grade to have r 10 vertical insulation at the slab perimeter extending downward from the top of the slab to a depth of at least 2 ft.

Depth insulation under concrete floor.

On the other hand if you are laying insulation on top of the existing slab than you will need to make sure that there are no construction. Phenolic foam is a popular choice to get around this issue as it s able to achieve strong levels of insulation for less depth. In this scenario a rigid foam insulation is usual and as you d want the same u value in the roof we need the same thickness of insulation 180mm. Insulation below the slab suits continuous low level heating gradually warming the thermal mass of the concrete and sustaining it at a consistent temperature.

Namely if you are only digging the slab you will need to take into account the thickness of the insulation since it will affect the depth of the slab. This allows an area for insulation and fill material under the slab. The first important thing to pay intention to is the depth of the floor slab. The target u value for a concrete ground floor slab is 0 22 and these days the insulation must be provided around the edge of the floor slab as well.

Many builders will baulk at this figure it was not long ago that installing 50mm of insulation in the floor was considered fairly advanced. Foamular provides r 5 per inch of thickness winter and summer. The math is pretty simple the thicker the concrete floor insulation material the deeper the slab will have to be. If the slab has hydronic tubing the minimum r value of this insulation increases to r 15.

If this is the situation you find yourself in the dpm will sit above the concrete and your moisture resistant chipboard will go on top beneath the flooring surface. Insulation is laid on the concrete and covered with a screed. Foamular does not absorb water like other types of foam board which makes it ideal for below grade and under slab installations. This stops any thermal bridging across the walls leading to cold spots.

In climate zones 4 and 5 the code requires certain slabs below grade slabs that are less than 12 in. Foamular 250 foam board. Excavate the area under the slab to 12 inches below the planned level of the top of the slab. Step 2 place 4 inches of gravel in the excavation.

Designers generally insulate both directly under the slab and around the perimeter as well. Home depot does sell the right solution for residential concrete slab insulation. In cold climates it is advisable to use a minimum of 2 inches of extruded polystyrene under the slab.