SOLAR HEATING SYSTEM CONSTRUCTION LOG
May 21, 2006: Thinking cool - installing solar attic vent
My Dad sent me a generous check for my birthday this year. Last year I used his check to fund the construction of my solar lawn mower. It only seemed right to invest in something solar this year too!
Summers in Maine can be hot. Last year I finally broke down and put a small window air conditioner in my office. While it is an efficient Energy Star unit, it does consume more energy than I would like. My Dad's check allowed me to purchase a Natural Light solar attic fan to remove the extreme heat that gets trapped in the attic space above my 2nd floor office. See diagram below for the theory of operation. I found this unit on the web from www.skylightguys.com for about $300.00. The unit was drop shipped to me by the manufacturer. Some of the big box hardware stores are now carrying these units, so check locally first if you want to save on shipping costs.
The instructions provided were quite clear. (Download them here - 231K pdf file.)
Installation is quite simple,
getting up there was a challenge. I borrowed my neighbor's extra long
extension ladder, and added my own step ladder to that. Then I just cut a
19" hole in the roof. The hole should be centered between the rafters
about 24" below the ridge. It is important not to cut through any rafters
or structural members.
Here is the vent ready for
installation, and the section of roof that I neatly removed.
After carefully preparing the
shingles, the vent is installed by sliding the upper half of its flange under
the shingles. I caulked 2 beads of roofing sealant around the bottom of
the flange first then screwed it to the roof with the provided stainless steel
screws. Finally I beaded sealant all around the the upper edge where
the vent meets the shingle.
Since my roof faces west - I had to orient the 10 Watt solar panel at it's maximum angle to optimize performance. You can see the thermal switch on the left side of the interior picture above. I stapled window screen across the inside of the hole to prevent bugs from entering. It turns out that paper wasps like building nests in that cavity. The fan is so quiet that I can't hear it running when I'm right next to it in the attic space.
I added a thermostat switch to make sure it only comes on when it is really hot in the attic. Without this - the fan will run any time it is sunny - even in the winter!
UPDATE: Sept. 2013. I have added an intelligent control for the fan that can also run it from house power. This clever unit has a remote control/monitor and sells for around $90. It is available from Costco and Amazon.
I later had to lay the solar panel down flat after installing my solar array, because it shaded the adjacent solar panel in the mornings.
July 18, 2006. Follow Up
I installed a thermometer in the attic with a display in my office that I can monitor. What I have seen is that the fan keeps the temperature up there at about 20-30F above the outside ambient temperature. On a day like today when it is 93F outside in direct sun, the attic is at 126F. Previously I would have seen temperatures in the 140-160F range on days like this. So I am reducing the attic temperature significantly. This results in less heat being radiated through the ceiling into my office space, and reduces the number of hours that I need to run my small window mounted (Energy Star rated) air conditioner.