GBlist: no roof ventilation

[Caaradrbl@aol.com]

On Mon, 25 Jan 1999 17:34:37 -0800 Richard Kadulski <kadulski@direct.ca>
wrote:


>A major reason for melting and ice damming

>at the eaves is that there is less insulation, and consequently higher heat
loss at the exterior

>walls, so melting and subsequent freezing can take place.

My (totally non scientific) observations on roofs with a large snow load at
temperatures approaching melting lead me to believe that the amount of
_insulation_ and not  ventilation is the key factor in preventing of ice
damming.  I guess to be more to the point the lack of heat entering the attic
space (wether by infiltration from the warmed space or conduction through the
building materails) is the determing factor.  I have seen houses with a great
deal of attention paid to ventilation hung with huge icicles and modulars with
little or no ventilation but great insulation hold their snow for days beyond
other houses in the neighborhood.  My baseline reference is usually nearby
garages and barns since they have no heat unless it is incidental soar (of
which we get so precious little here in Ithaca).
Rick Darfler
Cleveland Ave. Assoc., Inc.
Contractors, Ithaca, NY
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