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whole house fan

Post in 'The Green Room' started by amellefson, Jan 30, 2011.

  1. amellefson

    amellefson Member

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    I would like to buy and install a whole house fan this spring. It will make a nice alternative to running the A/C. Broan used to make a cheap one, but not any more. I have not looked since last year but I think they were in the 400 to 600 dollar range. Does anyone have any tips on shopping, I like the motorized insulated doors on some.

    Tony

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  2. maverick06

    maverick06 Minister of Fire

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    I went through this process last year. I had a attic fan growing up and wanted one with this house.

    What fan you want depends on a lot of factors
    1) What size house you have, this will dictate how large of a fan is needed
    2) attic ventilation, You need enough to support the fan. It you have a ridge vent, chances are you are ok.

    Other things to consider, Belt drive fans cost more money, but are usually quieter than direct drive fans.

    I have A 30" fan, I was limited to that diameter due to the width of the hallway I have.
    http://www.acehardwareoutlet.com/ProductDetails.aspx?SKU=55288
    The picture isnt quite right, its actually a 4 bladed fan, not a 6 as shown.

    As far as insulation, I build a foam box that goes overtop of it, in the attic, its plenty of insulation.

    For more reading, I suggest an unbiased site, the EPA: http://www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic=12357

    They recommend 30 to 60 air changes per hour. (Square feet______ x room height______) x 30 or 60/ 60 = cfm required _________.

    A word of caution, there are a few companies that sell fans that offer lots of insulation, such as Tamarack. They sell small fans that sit between the joists. Be careful with fans like that. The HV1000 fan costs over double the amount mine does, and moves only 20% the air! Thats a ripoff, just so you don't have the cut the joists. Dont do that, you will regret it, it does not nearly pull enough air to cool you, unless you have one per room!

    I love the fan, its lifealteringly good!

    You wont regret the decision (unless you dont like having the windows open!)
  3. GT26

    GT26 New Member

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    pacific NW
    When I remodeled I installed a central " plumbed" system. Panasonic I think.
    Its in the attic and has a hose to each room, then across each room is a filtered switchable intake.
    The main unit exhaust-es out the eaves with one way vent.
    At the time it was installed to meet code.
    It does a good job of bringing in fresh air, however it really doesn't cool unless we run it at night. Then it does a good job of cooling.
    If I could do it again I would bring the make up air in through earth tubes and a air handler.
  4. jimbom

    jimbom Combustion Analyzer

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    I don't want any unnecessary penetrations in my ceilings. And, I am cheap so we have a recycled fan. It is a forward-curved blade centrifugal fan that may have come from a furnace. We run it from late spring through mid fall. It sits on the floor and exhausts at a window that I can close for the summer. Mine has a 1/4 HP electric 115 volt, 5.2 amp motor. I put it on a timer to turn it off after a couple of hours. Somebody gave me this one, but you can pick one up for $25 or free from discarded furnaces.
  5. phatfarmerbob

    phatfarmerbob New Member

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    hudson valley ny
    I have a whole house fan in my cape cod ... its so great in the spring and fall ,,, even those cooler summer nights .. sometimes ill run it early in the am to cool the house down before turning on the AC, if all the door and windows are shut and i turn it on and open one window it will blow an amazing amount of air through that window ,,really neat thing to have in the house
  6. amellefson

    amellefson Member

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    This looks like great first hand advise. I will have to check it out in a day or two. Got to cut wood like crazy tomorrow before the snow flies. Luckily I have time until spring.

    Tony
  7. maverick06

    maverick06 Minister of Fire

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    No problem Tony, drop my a PM if you have any questions as i am not that good at going back to threads I posted on.
  8. mikeyny

    mikeyny Feeling the Heat

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    Some whole house fans can pull the exhaust fumes out of a gas fired hot water heater and distribute co throughout the house, be sure to have enough incoming air channels so this does not happen. Believe it or not, it happens quite often.
    Mike
  9. phatfarmerbob

    phatfarmerbob New Member

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    Very good observation the first time i turned it on the spring we got our house i didnt open any windows first and the cold fireplace gave my living room a nice coating of ash dust. needless to say i now clean the fireplace out before i start running the fan,,, i also usually have some windows open because thats kinda the point of the fan
  10. amellefson

    amellefson Member

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    I planned on always opening a couple windows but never thought of those possibilities. Thanks guys.
  11. semipro

    semipro Minister of Fire

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    Once you get it going you might need to find a way to hold bedroom doors open. They'll slam shut with a vengeance if you don't.

    I've installed whole house fans in several of our house and would strongly recommend getting a belt driven one. They seem to be much quieter than the direct drive units and don't vibrate your house as much.
  12. pyper

    pyper New Member

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  13. Indiana

    Indiana Feeling the Heat

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    I've been using one for 35 years. We love it. Saves us from using the A/C Untill July.
  14. Don2222

    Don2222 Minister of Fire

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    Hello

    I just did some testing on my whole house fan.

    It is 88 degrees F outside in shade and 94 Degrees F in the Sun and the attic is 109.0 degrees F.

    After running the Fan on High for approx 3 mins the temp in the attic went down to 93.2 Degrees F

    It is 85 Degrees inside!

    How is your fan working these days??

    Attached Files:

  15. laynes69

    laynes69 Minister of Fire

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    We have debated getting a whole house fan due to the temperatures upstairs being brutal during the summer. But after insulation and air sealing the attic we may not need one. Currently it's 87 degrees outside and sunny. It's 78 in the home and actually it's cooler upstairs than down. I account the downstairs as having some air loss issues. We also have 42 windows which we keep our curtains closed. At night then we run a couple box fans in the windows. For us insulation made things better.
  16. Don2222

    Don2222 Minister of Fire

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    Hello laynes69

    My house is a walkout split and completely above ground. I added alot of insulation and air sealing in the attic plus the radiant heat shield over the rafters!

    What type is yours? Is the basement below grade?

    How much insulation do you have in the walls?
  17. laynes69

    laynes69 Minister of Fire

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    Our house is an old Victorian around 150+ years old. It does have a basement which is underground. It 2400 sq.ft. with 10' ceilings.
    Some of the walls have urea-formaldehyde which has shrunk some but is around 8" thick. The rest of the walls are fiberglass. We had a blower door test done on the home and rated it as drafty as a barn. There's still more work to be done, but even with the heat outside I measured the ceilings upstairs at 79 which are warmer then the base of the rooms. We put in 14" of cellulose in the attic, which only had 3" last year. So far I'm happy with the results. With the number of windows we have next year we will invest in some insulated drapes. If we left the curtains open the heat gain would climb through the roof. Don, how much insulation do you have in the attic? From the photo of the fan it looks like there is very little. I would think that alot of heat will enter the living space from the attic. I think we installed around an R50.
  18. Don2222

    Don2222 Minister of Fire

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    Hello laynes69

    That pic shows the original New Ownens Corning R7 Fiberglass Building Insulations!!! On the paper back the stamping in big black letters is "ECONOMY" So in 1962 when the house was built they had R7 economy insulation!! LOL

    So I ripped it all out, rolled it up and hauled it all to the dump!!! Then I put down R4 Reflectix foil to air seal all the holes and to provide not only a radiant heat barrier to hold in the winter heat below but the polypropylene cover is also a moisture barrier. So then I added 2x2s to the 2x4 studs to make 2x6s and laid in R19 Faced Fiberglass and then crisscrossed it with R30 unfaced fiberglass for a total of R53 !! That saved 100 gallons of oil or 1 ton of wood pellets!!

    Attached Files:

  19. laynes69

    laynes69 Minister of Fire

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    Very nice! I'm sure it saved a ton. I had to go in and hand dig out every overhang where the previous jacka##es filled with cellulose. The overhangs were 2 feet deep so it wasn't fun. I then laid a floor protecting product across the joists to create a baffle. Our attic was 110 today with 90 and full sun outside, so my efforts have paid off. It's nice saving some green!
  20. DaveH9

    DaveH9 Member

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    NW CT
    we used a whole house fan for years, but now never use it. We found that it brought in too much moisture. It stirred up fiberglass dust from the attic, and expelled it into the area around the home, then sucked it into the windows. Not good. I installed a thermostatically controlled gable end fan that cools the attic, combined with ceiling fans we hardly ever need to use the small window AC. I am going to take out the whole house fan and put in a skylight. In the skylight channel I want to install a vent with a blower that will be ducted out side, providing ventilation with out disturbing the attic air.
  21. woodgeek

    woodgeek Minister of Fire

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    Dude--I thought the bubble wrap stuff only worked with an air space (or two)--did the stuff you buried have one? How did you seal it to the joists to achieve airsealing? Seems like the perimeter of your bubble wrap is WAY longer than just sealing the top plates of the framing and your penetrations....
  22. Don2222

    Don2222 Minister of Fire

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    Burying the foil worked fine because it is in the attic floor. That is the only place it works good like that. I know most professional installers put the foil over the insulation in the floor but that is because it is already there. Too much work to take it out. The best way to do it is to put it under the insulation. This way, any radiant heat in the living space below is bounced right back to keep it warm in the winter. Then the insulation keeps the rest of the heat in. I think it is not as efficient to put the foil on top and let the radiant heat travel thru the insulation and then bounce back thru the insulation! That does not make much sense!

    According to the info in the link below, I save 50-60% of the heat loss in the winter time not even counting the insulation!!!
    See >> http://www.greenatticpros.com/content/what-is-a-radiant-barrier

    As far as air sealing, I filled the wire holes with spray foam and then added an extra piece of foil over the interior wood wall top plate. Then rolled out the roll of foil. Then added the R19 fiberglass. So no air escaping!
  23. woodgeek

    woodgeek Minister of Fire

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    I'm really not trying to bug you Don, but I respectfully disagree that radiant insulation works the way you suggest. Without an airspace, any temp differential that arises between the foil and the surface underneath gets killed by conduction. A very thin film of air is an good conductor of heat--the temp of the foil and the drywall will be the same. If you doubt, why don't we just insulate our attics with 10 layers of foil (maybe a mm thick stack) and just skip the FG? Of course foils stacks are used in cryogenic applications, but all the air is evacuated out in between the foils.

    Did you use any sealant on the top plates, or just lay the extra foil across the top?
  24. Don2222

    Don2222 Minister of Fire

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    Hi Woodgeek

    I agree with you in theory that if it was a thin layer of foil buried under the insulation that it would not do anything. However in reality that is not the case. The foil is bumpy and in 2 layers with an air space in the middle. The Reflectix foil is also encased in polypropylene. So the plastic was really needed for the moisture barrier which of course is needed right on top of the wall board. Also I disagree that convection is taking place because it is more like the case of the heat nipples mounted on top of every electric water heater. Water heaters are plumbed with copper tubing which conducts heat very well. Heat nipples are made out of aluminum so no heat is conducted thru them. So in the case of wallboard and the foil, it is wallboard with a layer of polypropylene on top and layer of bumpy foil with an air space and another layer of foil and another layer of polypropylene on top of that. Then a paper backed layer of 6" Fiberglass crisscrossed with another 9" of fiberglass! If I took a temp measurement you would see the difference. Maybe I will sometime in the winter when I have a chance.

    No nothing else but two extra layers of foil and plastic over the top plate. However one layer of plastic will still air seal it!

    Attached Files:

  25. woodgeek

    woodgeek Minister of Fire

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    You're killing me man--the thermal conductivity of Aluminum is ~60% that of Copper, making it one of the best thermal conductors known (popular for CPU heatsinks). The nipples you describe are to block convection of the water inside the pipe, which is actually much more effective at carrying heat than conduction through a Copper or Aluminum pipe wall. This is achieved by the floating or sinking balls trapped inside the nipple.

    I also think it would be cool to measure the temps on both sides of your buried reflectix, come winter. Without an airspace, it is supposed to add about R-1, so you should get 1-2 degrees drop.

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