Cheryl writes from Fonthill, Ontario: "I am insulating the crawlspace of my sun porch which we have turned into a toy room. The crawlspace is about 2-2.5 ft headspace, the ground is dirt and there are gaps around the perimeter which are not sealed. I know small critters like squirrels, chipmunks, cats & mice run through the space. My question is whether I put the vapor retarder on the ground and seal up the gaps or whether I put the vapor barrier up against the insulation (but do I still have to worry about the critters?)? What is the best solution for keeping the critters out of my insulation but properly insulating the space?"

Answer: If the crawlspace under the porch is enclosed (with concrete blocks for example), the poly should be placed on the dirt and should overlap by 12 inches.

The vapor retarder for the floor should be as close as possible to the floor; painting the underneath of the porch with an oil base paint is sometimes easier.

Insulation should be installed under the floor. You can use fiberglass batts, which are held in place by their friction fit.

To help preventing critter nesting you can use extruded polystyrene rigid foam board insulation. With the foam, you will need to cut pieces to size and hold them in place with caulking that is not petroleum based. Be sure to to put insulation in the spaces between the joists up against the band joist (header).

Gaps around the perimeter should be sealed; low-expansion spray foam can do the trick, especially around service penetrations. Ventilation is critical to avoid moisture built up. A small mechanical fan exhausting to the outside is best.

If the perimeter is simply enclosed with a privacy lattice, seal the underneath of the sun room flooring with a super 6 mil poly, caulking and tape, and insulate with extruded polystyrene rigid foam board to help preventing critter nesting. Extruded polystyrene provides R-5 per inch and you can easily install two inches.