Insulated Concrete Floor Slab Detail

The layer of rigid foam insulation that separates the concrete foundation wall on the outside from the slab on the inside.

Insulated concrete floor slab detail. The climate the type of foundation whether the slab includes hydronic tubing for radiant heat and the severity of the local termite problem. Such spaces typically have a sound level concrete slab floor but lack sufficient floor insulation to achieve the thermal performance targets for new habitable rooms. Figures 4 12 through 4 14 show variations where the slab is the primary location for insulation. If headroom is tight then the only option may be to break up the existing slab dig further down and build up an entirely new floor.

Ground bearing floors shall be of adequate strength and durability and use concrete mixed and reinforced as necessary to support floor loads safely and resist chemical and frost action. Where the heating is likely to be turned on and off such as in new build domestic properties and a faster thermal response is required the floating floor arrangement of insulation above the slab can be more appropriate. This stops any thermal bridging across the walls leading to cold spots. Ground bearing concrete floor slabs should be at least 100mm thick including monolithic screed where appropriate.

Insulation below the slab suits continuous low level heating gradually warming the thermal mass of the concrete and sustaining it at a consistent temperature. Insulating a slab on grade depends on at least four factors. The slab on grade design calls for double stud walls insulated with dense packed cellulose what roche believes is the most economical and practical approach for getting the walls to r 40 or beyond. Figures 4 9 through 4 11 and 4 15 show configurations with insulation on the exterior surface of the foundation.

Consult appendix a table a6 3 1 in the 2016 edition for a tabulation of assembly f factors for slab on grade floors based on the arrangement and rated r value of the applied insulation. In this section several typical slab on grade sections are illustrated and described. Martin holladay explains insulating a slab on grade in the energy smart details department. 4 2 slab on grade construction details.

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. The f factors for slab on grade floors are defined in standard 90 1.