In this video, This Old House home technology expert Ross Trethewey helps a homeowner solve an ice dam issue with smart insulation practices that also improve the home’s efficiency.
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Home technology expert Ross Trethewey helps a homeowner solve their attic insulation problem. After getting some conflicting suggestions, the homeowner turns to Ross’s plan of turning it into an unvented attic space with spray foam insulation. Ross walks the homeowner through the process of testing the home, having the insulation installed, and testing the insulation quality.
What are Ice Dams?
An ice dam occurs when the heat from the home rises and melts snow on the roof, the snow melt (water) runs down the roof toward the unheated eve, and refreezes, creating a dam. The dam then causes more snow melt to back up, allowing it to seep under the shingles and into the home. This can cause damage to roof decking, insulation, drywall, and other materials, and the answer is insulation.
Where to find it?
Ross helps a homeowner suffering from ice dams by first discussing attic insulation options for vented and unvented roof systems. They then decide which system is best for the homeowner. Afterwards, installers install spray foam insulation to the attic roof rafters.
Vented roof – Keeps the heat in the building and then lets the attic vent to the exterior using soffit
vents, ridge vents, and gable vents. The advantage is there’s less volume of the home that needs to be heated and cooled because the “conditioned envelope” is from the ceiling, down.
Unvented roof – Puts the triangular attic space inside the “conditioned envelope.” Insulates the
attic with spray foam insulation to the rafters on either side of the roof line.
Ross performs a blower door test – depressurizes the home by pulling the house under negative
pressure, sending all the interior air through the fan, outside.
Ross performs zonal pressure diagnostics with a manometer – measures differences in pressure
between rooms to determine where air is leaking.
Ross checks the air leakage from the attic to the main floor by looking at vents and light fixtures
with a thermal imaging camera.
The installers apply a new industry standard spray foam that requires only a single application
and will expand to a 5” thickness.
Expert assistance for insulation was provided by Green Stamp Co. [https://greenstampco.com/]. Additional assistance was provided by Holcim. [https://www.holcim.com/]
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Fixing Ice Dams on a Roof | Ask This Old House