Best Insulation Over Concrete Slab

One option for insulating on top of a slab is to apply rigid foam insulation directly to the slab then install the subfloor on top of the insulation.

Best insulation over concrete slab.

Foamular 250 foam board. I wouldn t go as far as saying you couldn t use spray foam below a slab but i m not sure why you d want to. Yet expanded polystyrene eps performs as well or better than xps and at a substantially lower cost. Two layers of 3 4 inch osb subflooring then float unattached on top of the foam to provide a solid and stable underpinning for the wide board wood floors.

We recommend at least 1 inch of foam board. Foamular provides r 5 per inch of thickness winter and summer. There are several ways to install subflooring above the rigid foam. When building a slab on grade eps rigid foam insulation is the most common choice of insulation for performance and cost.

Spray foam for sure has uses where it is the best choice by a long shot but under a slab is not the place. 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. You can use either one or two layers of plywood or osb and the subflooring can either be fastened to the concrete with long tapcon screws or it can simply float above the foam. Allow this to dry then roll out 6 mil polyethylene sheeting over the floor to provide moisture protection.

Foamular does not absorb water like other types of foam board which makes it ideal for below grade and under slab installations. If your basement slab lacks sub slab foam you ll have to install the insulation above the slab. This method is simple but it has. Use a good quality foam board adhesive to adhere the foam to the concrete.

Tim healeyinstead of a conventional sleeper system to support the subflooring an uninterrupted layer of foam sits directly on top of the concrete slab. In climate zones 4 and 5 the code requires certain slabs below grade slabs that are less than 12 in. 4 where rainfall can be heavy use a fine tooth trowel to apply cold cut back asphalt mastic over the entire slab use about one gallon per 100 square feet of floor. Home depot does sell the right solution for residential concrete slab insulation.