How to Insulate a Bathroom Floor in a Crawl Space

Insulate the bathroom floor for comfort and energy savings.

A bathroom floor that is not insulated not only feels cold, but also allows cold air to seep into the bathroom, which increases your heating bills. Insulating a bathroom floor in a crawl space properly will also insulate heating ducts and hot water lines, resulting in even more energy savings. Choose a blanket insulation with the highest R-value possible within your budget to get the most savings, and comfort, for you money.

Things You'll Need

• Tape measure
• Blanket insulation
• Felt-tipped marker
• Utility knife
• 3-by-3 foot plywood, 2 pieces
• Contractor's stapler
• Staples
• Insulation hangers
• Chicken wire

Instructions

1. Measure the length of the joists with a tape measure.

2. Unroll the blanket insulation and measure the length of the joists for the bathroom floor with a tape measure. Mark the location with a felt-tipped marker.

3. Place a piece of 3-by-3 foot plywood under the cut mark with the mark approximately centered on the plywood.

4. Put a second piece of 3-by-3 foot plywood on top of the insulation. Align the edge of the plywood with the cut mark, approximately straight across the insulation.

5. Compress the insulation by kneeling on the top piece of plywood.

6. Cut the insulation at the cut mark with a sharp utility knife.

7. Place the end of the insulation in between the bathroom floor joists. If the insulation has a paper backing, the paper side goes toward the top. If the insulation has a vapor barrier, the vapor barrier side goes toward the bottom.

8. Secure blanket insulation that has a paper backing with insulation hangers. Insert the insulation hangers bowed upwards with the ends held in place with the pressure from the joists on each side. Staple vapor barrier insulation to the joists. Unfold the stapling flange on each side of the insulation and staple the flange to the side of the joists on each side of the insulation.

9. Position the insulation underneath bathroom heat ducts and water pipes, if possible.

10. Attach chicken wire across the bottoms of the joists with staples to prevent rodents from damaging the insulation.

References

• U.S. Department of Energy: Crawl Space Insulation
• Johns Manville: Insulating Basement and Crawl Space Walls