Our 850 sq. foot house has three soffit vents on the west underhang, but no soffit vents on the east underhang (nor roof vents on the east half of the gable roof. We have two (passive) roof vents on the west half of the gable roof.
1) Is this enough ventilation??2) Our garage in the back has no roof ventilation (believe it or not). Should I put in a roof vent and two soffit vents??
Cory Regina, Saskatchewan, Canada
"George E. Cawthon" wrote in news: snipped-for-privacy@worldnet.att.net:
This is the first time I've ever read that one can have too much ventilation. Are you sure about that? Every manufacturer's vent instruction and other recommendations I've read always phrase ventilation requirements as minimums. Never anything mentioned about problems with exceeding those minimums. They do indicate a 50/50 balance between high and low vents is best and, if there's an inbalance, the low vent free area should be greater than the high vent free area.
Doug
Sure there is, especially in cold climates. If you have a
50 mile an hour wind outside and enough vents to have a 50 mile an hour wind through your attic, that wouldn't be good. Now if you had 40 inches of insulation and it was tied down tight, it might be ok.What you really need (especially in a cold climate) is enough venting to get rid of the moisture but not so much that you have to have an unreasonable amount of insulation. An attic getting warm from sunshine during a cold day is much preferable to an attic that stays cold because of excessive ventilation.
Actually you have a point and maybe after you reach 18 to 24 inches of fiberglass or R 66 excess venting may not have much effect. Unfortunately, you can expect most people don't have that much insulation.
Actually, without considering ridiculous amounts of insulation, you will have heat escaping into the attic in cold climates. This heat will warm the attic enough to cause ice dams when outside temps are down low and the snow cover is insulting the lower levels of snow. Unless you get ridiculous with the venting, you can't have too much with this in mind.
Bob
True, so it all depends on the climate. Some places are cold but with little snow so ice dams don't form. I've seen icicles on some of our houses that were essentially continous along the eave and maybe 10 feet long. Thank god there were no damaging ice dams. But it was a clear indication that lots of heat was going into the attic, especially near the eave. The real solution, however, is more insulation, not more venting.
How about adequate amounts of both? :-)
But, I'll still hold out for reasonably maximum venting. When it snows a _lot_ and you get a deep cold snap of a week of two, your heating system is pumping full time to keep the house warm. The colder it is outside, the more you pump, and the more you pump, the more heat goes outside due to the differential. Even houses with thick insulation start to develop ice dams in these situations.
Bob
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