Tag Archives: energy efficient

Start with the basic principles that govern how energy crosses a building enclosure: convection (air leakage), conduction (movement through walls, for example), and radiation (of sunlight through windows, for example). I choose building components that best address energy flow by design, and that require proper installation, but not extra labor and skills, to make them work.

Can we build an energy-efficient, stick-framed envelope insulated with fiberglass? Sure, but it takes a lot of work and requires skill, persistence, and a ton of caulk. Air leaks through stick-framed walls at the top and bottom plates; between the drywall and the sheathing; around windows and doors; and through light fixtures, switches, and outlets.

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We can still use stick framing and dramatically reduce air leakage with properly applied sprayed polyurethane foam, reducing the need to caulk holes from wiring or plumbing. Foam costs 3 or 4 times as much as fiberglass, but if it’s applied as directed, it fits tightly, insulates, and doubles as an excellent air seal—far better than fiberglass. If we’re concerned about heat loss through studs, we can either  shear the exterior with rigid foam sheathing, or better yet, use SIPs, which eliminate a great deal of framing lumber.

I spray open-cell foam directly to the underside of the roof deck, from the ridge down to the tops of the walls, creating a conditioned attic. This stops air leakage to the outside through any penetration in the ceiling, eliminates the need for roof ventilation, and does not, in my opinion, lead to premature deterioration of the shingles. All HVAC supply and return ducts are within the conditioned space, access to plumbing and wiring in the attic is simplified, and recessed ceiling lights need not be airtight or protected from insulation. Admittedly this insulation method costs more, both because foam costs more than fiberglass, and because there’s more surface area to cover. Nevertheless, foam seals out air leakage better than fiberglass, and the home’s energy performance is greatly improved.

Read entire article at: http://www.homeenergy.org/show/article/magazine/130/nav/issues/id/1868?utm_source=June+4%2C+2013+e-newsletter&utm_campaign=HEM+Enewsletter&utm_medium=email

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