Thursday, December 11, 2008

Reading a Snowy Roof For Heat Loss

While engaged in a snowball fight with my daughter recently, I glanced up at the roof of our house. What were those strange patterns in the snow? The vertical white lines are the rafters, whose thick wood reduces the roof's exposure to the warmer air inside the attic. Chances are the dark spots, where all the snow has melted, coincide with where light fixtures stick through the ceiling, allowing hot air to escape into the attic from living areas. Using patterns of snow melt to figure out where you have leaks in your top floor ceiling is in the same category as a post on this website one year ago (12/17/07) about how to use indoor spider webs as energy detectives.

Update (2021): Better than the suggestions below is to use LED inserts that fit into the recessed lighting and block air from escaping.

 The way to stop all that hot air from escaping through the ceiling is to build boxes around the light fixtures, up in the attic. I've heard from an insulation contractor that the boxes can be made of cut pieces of drywall or styrofoam, and should be no closer than several inches from the light fixture, since the lights can produce a lot of heat. Another approach is to replace the fixtures with the kind that don't leak and can have insulation pushed right up against them. These are quite inexpensive, but they require fiddling with wires during installation. More info can be found elsewhere on the web about this.

1 comment:

Unknown said...

Good idea. Comparing your roof with your neighbors' provides some benchmarks.
Careful about boxing in recessed fixtures that are not protected by integral thermal switches (that automatically turn off the fixtures if they overheat).
Best, I think, to replace the unprotected fixtures with new, protected ones. Better than best is to remove the recessed fixtures and provide some other means of lighting, so that the ceiling is an uninterrupted surface of drywall (or plaster) with no penetrations, thereby minimizing the movement of air from the room into the attic.