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.

I made a small modification to the stock vent.  I added a thermostatic switch on a short wire that will hang down inside the attic, the fan comes with connectors to aid in adding this.  The thermostat  will only turn the fan on if it is above 90F in the attic.  I would not want the fan to run in the winter - removing much needed heat!  Solar dealers sell this thermostat switch separately for between $24 and $42!  I bought the part (# 317-1092) directly from Digi-Key  for about $8.00.  I had to add some wire and connectors and saved a bundle.

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.

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