How to Insulate a Porch Floor

Staple gun

An enclosed porch on the back or front of the house will not hold much heat, even if the roof and walls are well-insulated. Cold rising up from the ground directly under the porch floor will make the interior of the porch cold despite wall insulation. Manufacturer Owens-Corning recommends insulating the underside of a porch as you would insulate a crawlspace to keep the interior of the room comfortable in cold months.

Things You'll Need

• Fiberglass insulation
• Safety glasses
• Face mask
• Bread knife
• Staple gun
• Nylon straps

Instructions

1. Cut the insulation if it doesn't fit between the joists. A bread knife is an effective tool for cutting insulation. Flip the insulation so the vapor retarder faces you. Wear safety glasses and a face mask.

2. Place the insulation between the floor joists with the vapor retarder -- the paper side -- next to the floor. The insulation should run from one joist brace to the other, or end to end. Don't leave any spaces uncovered.

3. Staple lengths of nylon strap horizontally from joist to joist. Placing one strap every 3 feet or so should keep the insulation from sagging.

References

• Owens-Corning: Insulation FAQ
• Owens-Corning: Insulating Your Basement or Crawlspace in a Weekend