http://www.dannylipford.com/diy-home-improvement/heating-and-cooling/how-to-size-attic-exhaust-vent-fans-for-your-home/ Expert Advice on Home Improvement Fri, 20 Nov 2009 22:24:59 -0500 http://wordpress.org/?v=2.8.4 hourly 1 http://www.dannylipford.com/diy-home-improvement/heating-and-cooling/how-to-size-attic-exhaust-vent-fans-for-your-home/comment-page-1/#comment-46110 PaulZ Fri, 13 Nov 2009 05:05:27 +0000 http://www.dannylipford.com/?p=5544#comment-46110 Danny, I have 1921 sq./ft. of attic space. I need to find out how many holes needed in blocking between 22 1/2" center to center roof rafters for attic ventilation. The structual engineer on the remodel wants 2x6 blocks that will be 22 1/2" long with 2" diameter holes nailed to wall and to upper roof. I took the 1921 sq./ft. divided by 150 sq./ft. of area which gave me 12.8 or 13 sq./ft. of ventilation area. I'm in California so the code equires 1 sq./ft. of ventilation area per 150 sq./ft. of area. Take the 13 sq./ft and divide by 2 which gives you 6.5 sq./ft. of soffit vent area. I have to find the area of the 2" diameter circle which is [3.14(1 squared) = 3.14 divided by 144 = .0218055 sq./ft. per hole]. Then take 6.5 sq./ft. divide by .0218055 = 297 holes required. I can only fit (5) 2" diameter holes onto the 22 1/2 long blocking. Take 297 and divide by 5 = 59 blocks needed. Here's the spot that confuses me. The attic area only has space for only 47 blocks. I would like to install a roof fan, but would the 47 blocks be enough attic ventilation in the soffit area. I took 1921 sq./ft. x .7 = 1345 x 1.2 = 1614 CFM required for fan. Would a 1600 CFM fan be suffcient that I can reduce the number of 2" diameter holes in blocking? Do I need to install a gable vent? Thanks, PaulZ Danny,
I have 1921 sq./ft. of attic space. I need to find out how many holes needed in blocking between 22 1/2″ center to center roof rafters for attic ventilation. The structual engineer on the remodel wants 2×6 blocks that will be 22 1/2″ long with 2″ diameter holes nailed to wall and to upper roof. I took the 1921 sq./ft. divided by 150 sq./ft. of area which gave me 12.8 or 13 sq./ft. of ventilation area. I’m in California so the code equires 1 sq./ft. of ventilation area per 150 sq./ft. of area. Take the 13 sq./ft and divide by 2 which gives you 6.5 sq./ft. of soffit vent area. I have to find the area of the 2″ diameter circle which is [3.14(1 squared) = 3.14 divided by 144 = .0218055 sq./ft. per hole]. Then take 6.5 sq./ft. divide by .0218055 = 297 holes required. I can only fit (5) 2″ diameter holes onto the 22 1/2 long blocking. Take 297 and divide by 5 = 59 blocks needed. Here’s the spot that confuses me. The attic area only has space for only 47 blocks. I would like to install a roof fan, but would the 47 blocks be enough attic ventilation in the soffit area. I took 1921 sq./ft. x .7 = 1345 x 1.2 = 1614 CFM required for fan. Would a 1600 CFM fan be suffcient that I can reduce the number of 2″ diameter holes in blocking? Do I need to install a gable vent?
Thanks, PaulZ

]]> http://www.dannylipford.com/diy-home-improvement/heating-and-cooling/how-to-size-attic-exhaust-vent-fans-for-your-home/comment-page-1/#comment-44759 Peter Fri, 26 Jun 2009 12:48:26 +0000 http://www.dannylipford.com/?p=5544#comment-44759 Solar attic fans are not only the least expensive (in terms of total cost of ownership, which is purchase price + operating costs), they are also the most environmentally friendly way to ventilate an attic. Unlike conventional electric attic fans, solar attic fans don't use any electricity from the power grid at all! I have really been trying to get the word out about this method of attic ventilation at <a href="http://www.solar-attic-fan-info.com/" rel="nofollow">Solar Attic Fan Info</a> because I think not enough people are aware of the benefits - please check it out! Solar attic fans are not only the least expensive (in terms of total cost of ownership, which is purchase price + operating costs), they are also the most environmentally friendly way to ventilate an attic. Unlike conventional electric attic fans, solar attic fans don’t use any electricity from the power grid at all! I have really been trying to get the word out about this method of attic ventilation at Solar Attic Fan Info because I think not enough people are aware of the benefits – please check it out!

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