How To Install Rigid Foam Insulation Under Floor

Instead of installing the foam insulation between floor joists in the crawl space the foam board is installed against the crawl space foundation walls.

How to install rigid foam insulation under floor.

Squirt either caulk or expanding foam insulation in every hole or break in the floor. There are two ways to handle insulating concrete floors. The first step is to build the floor joist or to strip back the floor until you can see the joist. This foam board insulation is the rigid pink or blue panels that can be found at home centers in many different thicknesses.

But it is important to know how to install foam board insulation properly. 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. There are several ways to install subflooring above the rigid foam. It provides an r value of 4 per inch of thickness and is the cheapest type of foam board insulation.

Rigid foam insulation offers a thermal resistance between r 5 and r 8 roughly twice that offered by traditional batt insulation. If your basement slab lacks sub slab foam you ll have to install the insulation above the slab. Fill voids around the top of the wall where the foundation meets the floor framing and gaps around wiring. Unlike fiberglass rigid foam insulation does not absorb water support mold or allow air to pass through providing that joints between boards are sealed with tape.

In other words rigid foam can be applied on walls foundations and roofs and works great for both retrofits and new constructions. 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. Step 1 build the floors.

Install these panels over wall or ceiling cavities including those filled with existing fiberglass batts to boost the r value and improve home comfort and efficiency. Eps is used under roofing over foundation walls and beneath siding.