Thursday, Sep 27, 2012

Insulation information

Question: I have a 10-year-old, two-storey, 1,200-square-foot cottage in Windermere, BC. There is a 4' crawl space with insulated cement walls and poly covering 12" of 3/4 crush.

There are two electric baseboard heaters on opposite walls, and the thermostat set to 5 C year round. My hot water heater is down there along with the plumbing (plastic) and septic sewer lines running out of one wall.

I have not insulated the floor, nor have I put poly on the floor joists. I want to put laminated hardwood flooring in one of the bedrooms on the main floor.

Should I insulate between the joists in the crawl space before I put the flooring down?

- Eric

Calgary, Alberta

Answer: That's a great question, and I'm glad you asked it before you began installing your new floor.

According to the two major laminate suppliers I've checked with, there's no reason this flooring product can't be used in a seasonal dwelling that's completely unheated.

This also means there's no reason to insulate the underside of your floor as far as the laminate material goes.

That said, perhaps you may want to have a warmer floor under foot. If this is the case, then I can offer a suggestion. Insulating between floor joists with fibreglass is troublesome and unreliable.

Gravity pulls the batts down, and they're subject to moisture damage and rodent attack. A far better approach is to insulate the top side of your sub floor with rigid foam sheets, before installing a second plywood sub floor on top, then your laminate flooring.

An inch or two of extruded polystyrene foam placed under a 5/8" layer of plywood works well. The foam is rigid enough to support the ply without the need for strapping.

Just fasten the new ply to the existing joists with screws driven through all the layers. Put your laminate on top, and you're finished!

- Answered by Ken Evans, veteran woodworker and home improvement specialist for Canadian Homes and Cottages magazine.

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