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  1. #1
    Join Date
    May 2009
    Location
    Corpus Christi metro area
    Posts
    28

    Question Solar powered attic vent fan by Solatube?

    My new to me 1977 style, Texas U shaped ranch house, is going through the hottest summer on record, with heat index numbers between 103 & 115 everyday with no end in sight.

    My AC is running full time (it only cools down to 82 at night) and I keep the thermostat at 81. My electric bills are running over $300/ month. I have had the old AC condenser unit replaced and there are ceiling fans installed in every room except the kitchen where ceiling height is only 8'.

    In order to reduce the electric bills, I have read up on the current Solatube brand Solar powered fans (called Solar Star) that can be installed in place of an existing roof vent as seen here: http://www.solatube.com/homeowner/so...FSYoawodR1iUjw. Being solar powered, it costs nothing to run, so I figured it might just be the answer to the maiden's prayer.

    The solar panel is integral with the fan housing and it makes the single unit easy to install with no additional wiring needed. Each fan is rated at 850 cfm. According to their sizing chart, I would need 2 fans (near either end of the 4 in 12 gabled roof) on the longest straight roof section facing the street. There appear to be adequate soffit vents in the 18 inch roof overhang on both sides of the slope.

    Has anyone had any experience with these Solar Star fans from Solatube?

    Specifically, do they work as advertised to adequately cool the attic? Is a combined total of 1700 cfm for both fans enough to do the job for 1500 sq ft of floor space under that roof?

    Next, since it has been so hot, I haven't dared to get into the attic to scope things out. I assume that whatever insulation there may be is more than likely inadequate and will require either supplementation or replacement to reduce heat flow from the attic to the rooms below. Does it matter if I install a different type of of insulation (like foam panels) over what ever is there now? I surmise that the original insulation is either batts or blown in loose for that 1977 age bracket. Any comments on this approach?

    Finally, I have read about another product that is a special radiant conduction barrier that claims to reduce radiant heat conduction from the attic to the rooms below if placed on the attic floor OR reduce heat conduction from the roof surface to the attic space beneath the roof & hence further reducing conduction to the rooms below.

    95% of the heat transfer from the roof to the inside of the house is based on infra red radiant conduction, so this approach seems to have merit. Walls & windows are another issue altogether. My question here is has anyone used this material and does it meet the claims made for it? Their products are called radiant barriers as shown here : http://radiantbarrier.com .

    Has anyone used this and if so what do you think of it?

    Any help on this would be greatly appreciated.

    Ken

  2. #2
    Join Date
    Jun 2007
    Posts
    9

    Default Re: Solar powered attic vent fan by Solatube?

    I have put one of these in over an addition that I had built, I was having problems with heat build up and having a hip roof with a small ridge vent was not enough. The Fan was easy to install and has really done the job. Just cut a 14 inch hole in the roof removed a few shingles slid the fan in place and replace the shingle. It has been working a year now. No Problems

  3. #3
    Join Date
    Mar 2009
    Posts
    8

    Default Re: Solar powered attic vent fan by Solatube?

    That radiant heat shield is nothing new. Most insulation manufacturers make it as well. The use of the foil backing on either rolled insulation or on 4x8 rigid board insulation used on exterior walls before the bricks, stucco etc. is put up is mainly useful as a moisture and wind barrier. I'm not sure about all that radiant heat mamma jamma seeing as sun rays actually never directly shine on the aluminum shielding. AS for an attic i think just adding a layer of R19-36 rolled insulation with the plain paper backing would do the job. Most of the foil backed stuff is being used in place of black board on exterior walls and between the studs on the perimeter as well.

  4. #4
    Join Date
    May 2009
    Location
    Corpus Christi metro area
    Posts
    28

    Default Re: Solar powered attic vent fan by Solatube?

    Thanks for the replies guys.

    Glad to hear the fan actually performs as claimed. It makes it a little easier to swallow the $500 price tag for a unit installed by them where the install process is warrantied too.

    Black thumb, I too am a little unsure of the infrared barrier, even though their description of the heat flow process seems plausible.

    A brief review of basic heat transfer modes in plain English can be found here: http://www.bluffton.edu/~bergerd/NSC_111/thermo1.html but it does not satisfy the question of the manufacturers claim that 95% of all heat transferred from a roof surface is done by radiant heat flow since it is the least efficient mode of heat transfer.

    Just like cops, Thermodynamics professors are never around when you need one.

    Ken

  5. #5
    Join Date
    Aug 2007
    Posts
    6,940

    Default Re: Solar powered attic vent fan by Solatube?

    I don't have experience with this particular solar fan, however I am familiar with their standard solar lighting and can say without a doubt that Solatube is better than the competition. My suspicion is that their excellence would also extend to this new venting system as well.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  6. #6
    Join Date
    May 2009
    Location
    Corpus Christi metro area
    Posts
    28

    Default Re: Solar powered attic vent fan by Solatube?

    Love your tag line!

  7. #7
    Join Date
    Aug 2007
    Posts
    6,940

    Default Re: Solar powered attic vent fan by Solatube?

    Thanks.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

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