Insulation Materials Instruction

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Sizing Flash-and-Batt Rafter Insulation

Here's how thick the foam layer in a flash-and-batt system should be to avoid... More

Creating a Palette of Foam-Free Superinsulation Details

There’s more than one way to build a highly insulated, air-tight house—or to tighten up and super-insulate an existing home. Here’s a look at an evolving array of superinsulated details that don’t use spray foam. More

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Working With Roxul Insulation

A veteran contractor chose mineral wool insulation rather than cellulose for a... More

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Reusing Loose-Fill Cellulose

Working around existing attic insulation to seal air leaks may be more cost-effective than removing and replacing it More

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Fire Retardant in Spray Foam

Is it a potential health hazard? More

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Attic Insulation for Hot Climates?

It makes as much sense keeping the summer heat out as keeping the winter heat in. More

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Can Fiberglass Batts Perform Well in Tightly Sealed Houses?

I understand that fiberglass batt insulation can allow air to move through it and that this air movement degrades the insulation's R-value. Two causes I've heard about are wind-washing at the eaves and convective loops that can start in a wall cavity on really cold days and wick warmth from inside to the outside wall surface. But recently I have taken pains to do a very good air-sealing job on everything I build, whether it's an addition or a new house. I'm getting blower-door readings of less than 1.5 air changes per hour at 50 pascals. I also use baffles at the eaves, and seal the sheathing to the framing before insulating. Under these conditions - with air movement cut to a minimum - will fiberglass insulation perform at its stated R-value? More

Dow Structural Insulated Sheathing: A Solution for Coastal Walls?
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Is It Safe to Retrofit Exterior Foam Insulation?

Q: I built a lot of homes in upstate New York in the 1980s using 2x6 studs, fiberglass batts, and a poly vapor retarder for the shell. Given the rising cost of heating and cooling, the owners are asking about energy upgrades to their walls. I'd like to suggest adding 1 or 2 inches of rigid foam on top of the existing OSB or plywood sheathing, followed by new siding. Would the presence of polyethylene vapor retarders make this a risky retrofit strategy? More

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