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Tuesday, December 28, 2010

Frost on the Roof Tells Me a Lot

Mr. Frost is here again and for forensic roofers like me he has a lot to say. The melt patterns are like reading tea leaves, only more accurate.
Let it Snow right click and listen too in a different window.

A block of roof that melts before the others tells me that the area has either a cathedral ceiling or little, if any, insulation. The lack of air space between the ceiling and the deck on cathedral ceilings allows the heat to escape more quickly there.

Notice how the garage area stays frosted and the rest of the house roof thaws. Warm attics also show the outline of the rafters underneath the roof deck as the escaping heat, going as heat does to where heat isn't, melts the frost. The heat is thawing the rafters too but the have more mass to absorb the heat and keep the deck above them frosty. Plus heat wants to go up.

A well insulated attic floor will keep the heat in the home better making the roof thaw evenly. Homes that let heat escape more rapidly than others will keep ice on the overhangs but not over the living area. This leaves a border of frost on the outside edges of the living area. The overhang, porch, and garage keep ice on them longer.

Now comes the ice or snow torrent and you are under insulated. Weeee, we now have leaks inside the "warm wall." The ice builds up on the overhang but melts over the heated areas and you have a back up of water that goes under the shingles.

Shingles count on gravity, which turns water from one course of shingles onto the one below it until it reaches the edge or the ice dam. Smicsh dam, ice damn. Can be a flood. Wouldn't happen if you had used the leak protector. This caped crusader acts as a leak barrier for those moments when gravity lets you down.

Up north these products must be used: by code of ethics. But here in Dallas it'll never snow a foot. Never I tell you. Never, ever, nada, nunca, preposterous. That's like saying Atlanta Christmas snow. What an oxymoron. Up north, land of snow birds and tongues stuck to poles. I don't mean Slavic types but slobbering slobs. I am of Polish descent anyway. At least it is part of my 57 flavors. Yet despite temptation I've never licked a frozen pole. No paramedics for me, as we say, "nyet."

Back up on the roof the heat is escaping. Oh no! Plug the turbines. Hurry.

Now do you do this. It is forbidden and foolish. If you lived by the ocean and plug your turbines you might miss the the high hopes hailla ball. Plus your decking will rot and why you sing about the good things and the sun that lights the day, your roof will come down like a Led Zepplin.

Think about it. The heat has escaped and is now melting the ice on the roof. Do you think plugging those holes will do more than just make the ice melt faster. There will be so much condensation in your attic that icicles may form that later drop and put holes all over your ceiling.


Remember that ventilation was invented by northern pain companies in the 1920's because their paint would peel off the homes in the winter.

Happy New Year.

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