Hardwood Flooring Insulation Tips

Floor insulation comes in rolls, similar to the roll in this photo.

Hardwood floors over unheated basements or crawlspaces are likely candidates for insulation. Insulating these types of floors will make your home warmer, save money on heating costs and can reduce the noise level in your home. If the underside of the floor is accessible, the insulation can be added from beneath the floor without the need to remove the flooring itself -- otherwise you are looking at removing the hardwood floor, installing the insulation and replacing the flooring. Insulation generally used under hardwood floors is known as batts, which are rolls of a spun fiberglass material. The thickness of the fiberglass determines the "R" value, or the amount of insulation afforded by the batt.

Things You'll Need

• Caulk
• Caulking gun
• Rolls of fiberglass batt
• Tape measure
• Carpet knife or large scissors
• Breathing mask
• Gloves
• Long sleeve shirt
• Staple gun
• Furring strips

Instructions

1. Caulk around all wires and pipes that extend through your floor to prevent cold air entering your home from these sources.

2. Measure the length and width of the first joist you want to fill. Measurements should be taken from the underside of the floor if at all possible, so that installation of the insulation can take place from below the floor without the flooring itself being disturbed. You will be filling the empty space between the floor joists.

3. Unroll enough insulation material to fill the length of the joist you want to fill. Use a utility knife or a large pair of scissors to cut the insulation to length. Cut the insulation approximately two inches longer than the space you are filling so the insulation will be just slightly compressed, and friction can hold the insulation in place. If there is paper or foil on one side of the insulation be careful not to damage it in any way.

4. Cut the insulation to the proper width. In many cases no cutting will be necessary as insulation comes in the proper width for most flooring joists. If the insulation must be cut for width, make it approximately 1 1/2 to 2 inches wider than the joist area you will be filling so that the insulation will fit snugly into the area and friction can hold it in place.

5. Press the insulation into place, with the paper or foil side facing up (toward the underside of your hardwood flooring). Press the insulation so the paper or foil is in contact with the underside of your floor, but do not compress the insulation any more than absolutely necessary, as compression will reduce its insulative properties.

6. Fill each joist cavity in the same way. If the batt comes with flanges on the underside, staple the flanges to the joists to hold the insulation in place, otherwise friction should hold the insulation in place, or small strips of furring wood can be nailed or stapled across the bottom of the joists at 24-inch intervals to hold the insulation in place

Tips & Warnings

• Check with your local building department to determine the minimum "R" value needed in your location.

• Always wear long sleeves and a breathing mask when working with fiberglass insulation -- tiny pieces of fiberglass from the insulation can cause unprotected skin to itch.

References

• This Old House; Insulating a Floor; Tom Silva
• John Mansfield Homeowner: Installing Floor Insulation
• Bonnevile Power Administration: How to Insulate a Floor