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
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Send the tech guys to fix a roof. Come on
Black Mold Hat…
I have worked in Energy efficiency for over 35 years and consulted with various professionals in the industry who have concluded that it is far more cost effective to insulate and air seal an attic floor as opposed to doing a roof line.
In the episode you ran a blower door test and showed the major passage of air leakage to the attic which could easily be air sealed and have an additional R30 of cellulose blown on top of the existing fiberglass. They could also then close the gable vent add some soffit venting and perform any duct sealing and insulation that is needed. For an approximately thousand square-foot attic this work could be done for approximately $5000.
This attic was easily accessible with a stairwell and if a conditioned space was desired then that’s fine. But to represent that spray foam was a more effective route is a disservice to your viewers.
You did not disclose what the blower door test reading was but that attic seemed perfectly suitable for a traditional air sealing and insulation job at the floor level.
I would be interested to know what the cost of removing the still functioning fiberglass, and spraying foam over 30% more square footage of the area would be, my experience has been it’s at least three times more money. This also adds More square footage to the heated space which would likely raise heating cost, and still not achieve an R 49. I have been involved with the retrofitting of over 1000 homes with ice dam issues that were easily rectified by appropriate air sealing,ventilation and insulation.
There are also some concerns over the chemical content of spray foam it’s inherently higher carbon footprint, it’s noxious fumes with low flame retardants, the possibility of affecting a roof warranty the possibility of excessive condensation in the attic. I’ve seen many cases where the foam is shrinking away from the roof rafters. I agree and have contracted many jobs where spray foam was used appropriately but I think you did not give a fair evaluation of the two competing ideas as to how to correctly insulate an attic, especially in a cost-effective way.
@6:10 I'll Spank You?
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Closed cell spray foam should be the industry standard. It also negates the need for a vapor barrier when it's used in new construction.
Nice name ????
Another great episode, but I think we missed something. That wallpaper might not be up to code. ????
That last part…..yikes! Like the fine print on a pharmaceutical commercial.
Should have removed the old insulation before they sealed the attic with foam. Now the only way to get it out is through the house. They could have tossed it out through the gable vents and not had to haul it through the house.
Ross was looking for ghosts with that machinery