How to Insulate a Concrete Floor and Save on Energy Costs

Although concrete has some insulating properties, a concrete floor that is not insulated allows heat to escape from your house. Insulating your concrete floor can cause you to save significantly on heating and cooling costs, as well as cut down on the coolness of the floor during the winter months.

For this method of insulating your concrete floor, you will be building a plywood sub floor that can be insulated and covered as appropriate for the space. If you already have carpet on your concrete floor, you should be able to peel it back and reinstall after your insulating is complete.

To insulate your concrete floor, you must start with a flat, dry floor. If you have regular flooding in the area, such as it common in a basement, fix that problem before proceeding. You should also measure between the floor and the ceiling to see if you have enough room to insulate the concrete. Keep in mind that the distance between the two must be at least 7 feet 6 inches, so you should have at least 7 feet 8 inches of clearance before beginning this project.

Before beginning building your sub floor, clean the existing concrete you will insulate. For a vapor retardant, use 6 mil polyethylene sheeting to provide a barrier between the insulation and concrete. Be sure to overlap and tape seams: six inches of overlap is best. If the sheeting is slipping, use caulk to adhere it to the concrete.

Add pressure treated 2x4 sleepers around the perimeter of the concrete. Nail them to the concrete using a nailer for concrete or 2 ¼ masonry nails. Once there are 2x4 sleepers attached to the perimeters, run more sleepers in one direction, wall to wall. The sleepers provide the structure that the insulation will be placed in. They should be 16 inches apart from the center of each piece and attached to the concrete.

Once the sleepers are installed, you can lay the insulation. Use rigid foam insulation cut into strips to fit between the sleepers. Use a rigid foam insulation that is 1 ½ inch thick; you should never compress insulation to fit a space.

Finally you should cover the insulation with ¾ inch plywood. Run the plywood perpendicular to the sleepers and over the insulation. Stagger the seams between panels; just start with a half sheet of plywood every other row. Fasten the plywood to the sleepers with nails or screws spaced 6 to 8 inches apart.

Once the plywood work has been completed and the insulation completely covered, you should be able to finish the floor in any way you like. Carpeting is a popular option, but don't discount using tile or any other flooring method that fits the decor. If you do decide to use carpeting, consider using a carpet pad for extra insulation.

If this project seems a little intimidating, consider hiring a contractor to install the sub floor, leaving the finish work for you to complete. You could also hire a contractor to complete the entire floor, leaving you to enjoy your warm floor without the potential heartache of a half finished project.