Why wouldn't shingle color affect ice damming?

Specific Inspection Topics Roofing Inspections
1

Hello,

I live in Maryland. It can be 60 degrees one day and 14 degrees the next. The weather changes fast. We got all of our shingles replaced recently and I insisted we get the lightest color that they had. The salesman mostly had really dark colors! I get it. So it doesn’t show the algae and looks newer longer. Still, we want a cold attic crawlspace, right? If you had a black tent and a white tent, I’m sure it would be hotter in the black tent, no matter how many fans you directed at the inside.

But nobody else seems to be saying so. As though the only heat that matters comes from inside the house. Except maybe in Texas where they foam between rafters (I think that’s the new EIFS, and a bad idea) and put up radiant barriers.

Not my house but near me is a very posh neighborhood where people have attics that have a nice big window so they get that greenhouse effect that heats up their attic crawlspace. I can walk around and the houses where the window faces south or west have all of their snow melted earlier - and the ice dams were impressive. For Maryland.

Thoughts?

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I forgot to say, you could probably see how hot the roof is getting where it’s not blanketed by snow, if you had a thermal camera.

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How long do you think dark shingles are going to hold the heat prior to a snow? Sure, shingles have a pretty decent thermal mass but once you remove the radiation energy (by covering it with snow), things are going to cool pretty quick.

Yep, the black shingles will hold a little heat for a moment, but is it enough to melt the snow and freeze to ice? Nope.

But a constant warming from the attic will.

Lighter color shingles will keep you cooler in summer because they will reflect some energy.

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4

The reasoning is all lopsided. Black has a higher heat emissivity than light colors. Light colors merely reflect more sunlight. a perfect example is a teapot.

Teapot are shiny to keep heat in. Coal and wood stoves are flat black to EMIT more heat.

I’ve lived in Maryland all my life. Properly installed roofs do not have ice dams.

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5

Under the right circumstances, ice damming could still occur regardless of the shingle color. Did you insist that a water and ice barrier be installed? Best practice is to roll it over the sheathing edge onto the fascia.

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