Cavity Fill

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Installing Dense-Pack Cellulose

This economical material both air-seals and insulates More

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Tightening Up a Two-Family House

Chasing down and fixing energy leaks in an old house can be tricky and expensive,... More

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Getting Quality From Fiberglass Insulation

To get the most from fiberglass batts, you have to start thinking about insulation at the framing stage and coordinate with other subcontractors. An insulation contractor explains. More

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Island House Makeover — Insulating the Skin

In the teeth of a record-breaking winter, Thompson Johnson Woodworking wraps the... More

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Adding an Insulated Envelope

An airtight "puff jacket" achieves near Passive House levels. More

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Wrapping an Old House in a Passive House Puffy Jacket

Mid-coast Maine builders EcoCor, Inc., are applying their characteristic insulated wood I-joist exterior wall system package to an existing old house. More

Cavity Fill Instruction

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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

Choosing insulation for a high-performance home in Northern Vermont requires... 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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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

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