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Insulation/ice dams

jcraft's Avatar

Join Date: Aug 2002
Posts: 355

09-26-05, 09:27 AM   #1  
Insulation/ice dams

Okay, here is the background. Have a 1940's cape house with a 900 sq. ft attic that you can walk. Their is a vent at each end about 8" wide by 24" long. they put a new roof on last year with ridge vent. They scraped off 2 layers of roofing material. Now last winter we had ice dams along the front of the house like we have never had before, it was terrible. It is probably due to poor insulation and venting they say. There are no eave vents at all. So I am goint to start this year first and insulate the attic better,it has the old blow in insulation throughout the attic which is about 12 years old. If I lay bats of insulation over the existing insulation am I going to make the ventilation throughout the attic worse now. I am figuring next year on putting a little more ventilation up there. But I don't want to jeoperdize the airflow this year by adding the insulation. let me knowe what you think. Is it possible that just insulating the attic alone may help the ice dam situation. Thanks

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em69's Avatar

Join Date: Jul 2005
Posts: 857

09-26-05, 10:21 AM   #2  
If you can only complete of the two items this year due to financial reasons, then I would be installing some eave vents before insulation.

A good venting system allows for a continuous flow of air which enters the roof cavity at a low spot in the roof (for example, under the eave) and exits the roof at a high spot (for example, at or near the ridge of the roof). A good venting system works adequately by means of a natural convection current where warm air rises and pulls the cooler, drier air behind it. A good roof venting system must also be designed in such a way as to provide for proper air flow at all portions of the roof.

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