Low Energy House

Low Energy House - About Insulation - Concrete Floor

Concrete floors can lose heat through the ground under the floor as well as through the floor perimeter. The amount of heat lost depends on the size and shape of the floor area and the temperature difference between the inside and outside of the house

Floor Insulation - Concrete Floor

Expanded Polystyrene Solid Floor Insulation - Image Provided by Styrofoam™Concrete ground floors can have high density rigid board insulation fitted above the concrete slab or below the concrete slab. If insulation is installed above the slab, the building will heat up and cool down quickly in response to the heating system.

If the insulation is installed below the concrete slab the thermal capacity of the building will be increased and the concrete floor structure will absorb heat and release it into the rooms gradually over a period of time.

Thermal Bridging - Concrete Floor

To avoid cold bridging at the wall to floor junctions, it is usual to continue the wall insulation down level with the bottom of the concrete slab or to install 25mm of rigid board insulation vertically between the edge of the concrete slab and the blockwork inner leaf.

Compressive Strength of Floor Insulation

It is important that the insulation material has sufficient compression resistance to withstand the effects of compressive loads.

Concrete Floor - Damp Proof Membrane (DPM)

In a concrete ground floor, it is normal practice for a damp proof membrane is positioned below the concrete slab and lapped with the damp proof course, in the surrounding walls, to protect the structure from the ingress of moisture.

Concrete Floor - Vapour Control Layer (VCL)

Solid Ground Floor with Insulating BoardWhere there is no screed and there are sensitive floor finishes, a vapour control layer/slipsheet must be fitted between the insulation and the floor finish to protect them from moisture produced by the concrete slab drying out.

In addition to the DPM a vapour control layer (VCL) must always be positioned on the warm side of the insulation.

Underfloor Heating Systems - Floor Insulation

In concrete ground floor situations underfloor heating pipes or cables can be fitted in the concrete slab or screed. In either case the rigid board insulation must be located below the heating system. In a solid concrete floor the position of the insulation is important in either exposing the thermal mass of the concrete floor to the heat provided by the system or isolating the thermal mass from it.

Where the heating is provided intermittently and a fast response time is required, it is beneficial to have less thermal mass and so locating the insulation below the screed or timber floor and above the concrete slab is the most efficient solution.

Commonly Used Concrete Floor Insulation Materials

Extruded Polystyrene Concrete Floor Insulation
Extruded polystyrene rigid foam insulation boards, with high compressive strength, below concrete slab or screed.

Urethane Concrete Floor Insulation
Rigid urethane insulation boards with aluminium foil on both faces, with high compressive strength, below concrete slab or screed.

Phenolic Concrete Floor Insulation
Rigid phenolic insulation boards with aluminium foil on both faces, with high compressive strength, below concrete slab or screed.

All insulating materials must be fitted in accordance with the manufacturer’s instructions

It is important that the insulation layer at the junction of the floor and the external walls is continuous, in order to eliminate thermal bridging which can cause heat loss and create localised condensation and mould growth

About Insulation - Concrete Floor - Home Insulation