I have a small old two story house, and the top floor gets very hot during the day. I'm thinking of installing one or two roof turbines, and also am considering putting some insulation in above the ceiling, under the roof (I'm sure there isn't any right now). I'd like to hear some opinions about these ideas, and would appreciate any other suggestions. I like the idea of the roof turbines because they don't require anything but a little wind to operate.
John
First I suggest you make sure the attic is vented according to the local norms. Old homes often have insufficient ventilation. Just adding turbine vents will not fix it. You need to have a way for fresh air to get into the attic (usually soffit vents) and a way for the hot air to get out, usually ridge or other vents placed high on the roof. In most areas this is sufficient.
Insulation is a must, and even if you have some now, more is always better. You also want a vapor barrier. What makes a good vapor barrier depends on what your local weather is like (where do you live?)
Turbines are for those few areas or construction situations were standard static venting does not work well. If you do decide on turbines, I strongly suggest you get top quality units as the cheap ones are subject to sort life, leaks and noise.
I suggest you look at the Building Science Corporation web site. It has * researched * information on venting and related issues. Climate is an important part of deciding whether or not to vent an attic. TB
That's nice to know...if the convection drives the turbine than it would actually turn without any wind. I like that 20 deg drop you got, that would be very nice in my case...although your turbine was probably vented the entire garage, not just the roof-celing area.
John
other
I didn't mention but this house is in Southern California, just outside Los Angeles in the SM Mountains, an area called Topanga Canyon. I will check the old vents and also look to see if there are soffit vents. I know there is one high vent at one end of the house, the other end is two stories up and will be harder to check.
I plan on replacing the ceiling in the living room and that would be a good time to add insulation. I didn't think of the vapor barrier, what exactly would it do? Is there a specific kind of vapor barrier I would need. Also, would someone suggest the rating of the insulation I would be looking for(thickness, R-? rating). I don't think there is much area underneath the roof, I've only seen it once and I believe it was about
2 feet at the peak. The celing in the living room doesn't start at the top of the wall but rather is angled for about a foot from the walls and then becomes horizontal. That angle is following the angle of the roof rafter(joist?) and I'm wondering if it may be covering up the place where the soffit vents would be.John
other
What I wonder is if the convection is enough to turn the turbine, why bother with the turbine when you already have the strong convection?
I read a project report once that said convection venting was more efficient with a "tall" vent pipe than with a turbine. I believe the vent pipe in that case was dark coated for solar heat absorption, thus aiding the flue effect (along with some extra height).
Bill
But turning them and the outgoing air takes energy, which slows that air, compared to a gable or ridge vent or thermal chimney with the same area.
Nick
My impression was that the point of a turbine isn't to be efficient, although on a windy day, it helps. The point of a turbine is to keep crap (and vermin) out of the vent pipe. Wasps don't like it when their house moves.
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Which is a really good indication that you did not have enough high vents to start with. Likely any added vent, including passive (ridge or any non-powered roof vent) would have done very well. The turbine vents can add some additional venting when there is a wind.
No they don't need wind to move. The natural flow of warm air will cause them to turn, but that turning is actually slowing down the movement of the air, you would get more movement if you removed the part that turns.
I agree with you about the value of the turbine component. I think they are primarily for the entertainment of the homeowner. :)
Bill
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