View Full Version : To vent or not????
10-23-2005, 05:06 PM
This question is off topic but have gotten great responses in my p0revious posts and I have a dilema. Last year, we where paying 0.67 per THERM and the latest cost is 1.17 not including delivery and taxes. I added some insulation during this summer and also install those foam shutes on every rafter to vent the attic. I have notice that its temperature flactuates with outside temps. Hot out-side leads to hot attic and vice versa. I started helping a friend and he decided to foam the vents by the eves no venting shutes. I feel really dumb because when the temperature outside is cold the attic is a lot more more warm than the attic at my house. I am really tempted to remove those venting shutes and just foam the opennings. I know that lack of venting dimishes the shingle life but if that leads to a more comfortable house I can live with that minor problem. What else caan go wrong feel free to peach in!!!!
10-23-2005, 05:12 PM
I would think you'd get severe ice dams whenever it snows. Moisture condensing on the inside of the roof structure may lead to wood rot. It will get really hot in the summer.
10-23-2005, 06:41 PM
The idea of the venting is to get the attic area as near to the outside temperature as possible. Then no ice dams, etc will occur. Usually the vent formula is ; 1 sq ft of vent to every 300 sq ft of attic floor area.(50 % at soffit, 50% at peak) This is a minimum, the more the better.
As long as you have an adequate R value on the ceiling (attics floor) there is no problem.Depending on your localities climate in the winter, an r 28 insulation is a minimum start, R 40 a lot better.
10-23-2005, 07:18 PM
I wouldn't block attic/soffit vents or impair that in any way.
the minumums been stated.
consider a power roof vent to maintain reduced summer temperatures in the attic and thereby dropping structure heat gain.
you can also install a humidistat to control the attic air in the the winter.
It might be helpful to search what Lstiburek's company "Building Sciences Corp." would recommend for attic ventilation. Lstiburek has been very vocal on the subject of attic ventilation, mainly recommending a non-ventilated design for hot-humid climates. But he may well recommend against doing this for colder climes. Trust what he says -- not only does he understand the laws of physics which are the same North and South, but the guy is from Canada.
It is my impression he will warn against anything which could promote formation of ice dams. But living in S.Texas myself, Lstiburek will have studied it more than me<g>.
Best of luck -- P.Student
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