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Turbine vs ridge vent


JERP's Avatar
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Join Date: Jan 2003
Posts: 18
CAL

06-09-05, 07:22 PM   #1  
Turbine vs ridge vent

I am preparing to replace my roof. I'm also entertaining the thought of adding additional roof ventilation. The enclosed attic space is roughly 24'x50' reactangular area with a single ridge line. The roof has a fairly low slope. The attic is around 3' high at the ridgeline. I live near the California coast and there is constant wind that travels lengthwise across the home. Sometimes it's a breeze, but usually a 10-20mph wind. The weather in the Calif central coast area is pretty mild. It seldom freezes, temps from 30 - 90.

All I have currently is a gable-soffit system. One of the gables faces the wind, and so becomes an inlet. I can feel the breeze coming in the gable vent. The reason I want more ventilation is that the attic gets well over 30 degrees warmer than the outside air in the summer. Cosmetics are not an issue.

Under these conditions, would you recommend a turbine, a ridge vent, or nothing? I'm not too interested in an active system.

 
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resercon's Avatar
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Join Date: Nov 2001
Posts: 1,873
NJ

06-10-05, 07:30 AM   #2  
30 degree difference is actually pretty good. Especially when you consider the amount of solar heat gain in California. While there is no such thing of having too much ventilation, it is highly unlikely that adding more vents or even using passive or active ventilation will bring down the temperature any more. If it did, it would not be that significant.

There is a very good reason for that. Thermal Mass is anything that can collect and hold heat. Nearly everyting in the attic has this property, coupled with the amount of heat gain during the day, even with induce convective heat transfer (active ventilation), the BTU input would be greater than the BTU output from the attic.

The reason why you attic experiences just a 30 degree difference from the outside is probably due to the amount of wind pressure the attic is exposed to. You find that most house experience a far greater degree diference, even with an attic fan.

The last factor you have to consider is that every time you cut a hole in your roof, you increase the chances that the roof will leak. Regardless if it is a turbine fan or a ridge vent. If the installation of such devices reduced the attic temperature significantly like 50 to 80 degrees, then the installation outweighs the risks involved. In your case because your attic temperature is clearly well below the average attic and it is unlikely that the addition of more ventilation would accomplish anything significant. The installation of more ventilation does not outweigh the risks involved. So I would not recommend the installation of any more vents than you already have.

 
JERP's Avatar
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Join Date: Jan 2003
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CAL

06-10-05, 05:19 PM   #3  
Thanks of the info. I'll replace the roof without adding anything. I will monitor the attic temperature this fall get a more accurate idea of what''s going on.

My house is 40 years old and uses planks instead of plywood sheathing. Should I replace the planks with plywood sheathing? I'd rather not.

 
resercon's Avatar
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NJ

06-10-05, 06:40 PM   #4  
If the planking is in good shape then just leave it. However, it is a good idea to go into your attic and inspect the planking to see if there is any deterioration or damaged planks. Also if you have a contractor give an estimate, make sure he puts in the estimate the costs for replacing planks that are damaged or repairs that may come up once the roof is stripped. Make it clear that he will be held liable for not replacing or repairs to the roof decking once the roof is stripped.

 
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