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  1. #1
    Join Date
    Oct 2009
    Location
    Lake Zurich, IL
    Posts
    60

    Possible to closeup wholehouse fan by installing Powered Attic Fan?

    Please at least read this first post.

    It doesn't appear that this specific situation (especially no possiblity for soffit vents) has been addressed before.


    My wife and I moved into a two-story 1969 frame home in Chicago suburbs that has:
    - NO Soffit vents and house style PROHIBITS creating them. (The roof line cuts into the second floor and creates a "cove" on second floor rooms.)
    - Approx 1300 sq feet attic space.
    - The original whole house fan (which nicely cools off the second floor in 15-20 min on the hottest week day evenings after coming home from work when opening basement windows -- concrete basement floor dehumidifies the air). To try to minimize winter heat loss, I made a plywood box with removable lid that is insulated by the blow-in insulation on the sides and fiberglass matt on the top.
    - about 9" of original fiberglass batt in attic PLUS 18" of new blow-in insulation.
    - Large N-S gable vents totaling approximately 6+ square feet.
    - new asphalt roof, but it has a cheapo ridge vent consisting of what looks like a big brillo pad.
    - New Lennox furnance and A/C.
    - three wood fireplaces (one with a new wood insert). The other two will be sealed soon.


    MY IDEA I'm seeking feedback on:
    - Installing a power attic vent to cool off attic with the hopes of permanently closing up the Whole House Fan.

    Given the existing 6+ square feet gable vents and in ability to install soffit vents, this appears to be one of those rare times when a Powered Attic Vent may help to minimize A/C usage.


    P.S. All the duct work in the house (90% plus behind walls/floors) appears to be leaky.

    P.S.S. This is our first house. Had I known what I know now about HVAC, building envelope, etc, we wouldn't have bought the house.

  2. #2
    Join Date
    Oct 2009
    Location
    Los Angeles
    Posts
    38
    The powered attic fan will likely increase cooling costs unless you did a very good job sealing the attic floor before blowing in the new insulation (or if you blew in something like foam that seals on its own).

    If the attic floor is well sealed, consider a good (20-30 W) solar fan, which will run on sunny days and will not use additional electricity to operate.

  3. #3
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    why do you want to permanently close up the whole house fan? You've indicated you like the way it cools your home on even the hottest days?
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  4. #4
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,223
    Quote Originally Posted by tipsrfine View Post
    why do you want to permanently close up the whole house fan? You've indicated you like the way it cools your home on even the hottest days?
    Setting yourself up for another beating from Ted?

  5. #5
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    What if the attic never got too hot, or too cold, in the first place?

    That can happen if the attic is sealed and insulated at the roof deck.

    You could then open windows upstairs and run ceiling fans and possibly be comfortable on evenings when outdoor air humidity levels are not too high. In winter the sealed, insulated attic will take a healthy bite out of your heating costs.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  6. #6
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    Quote Originally Posted by chuckcrj View Post
    Setting yourself up for another beating from Ted?
    I'm setting myself up for a good Ted beat-down. I'm not done with my whole house fan research, but I've been accumulating a good number of scientific articles in support of my idea. I already know there are climates where it's a slam-dunk, but I'm not done making it work in Missouri by any means. Ted's not the kind of guy you go after when you're "weak in the ammo", so I have much research left to do.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  7. #7
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,763
    :-)

    Get a dartboard. List a bunch of guesses on slips of paper. Get a blindfold. Play "hokey pokey" in the background and get on with the poke n hope.

    Or you could get an audit and comprehensive home assessment which will list your homes deficiencies, cost of correcting, and estimated energy savings for same.

    Measure, model, diagnose. The scientific way to increased comfort and lower bills. Every house is different, and a 5 minute diagnoses wouldnt make me confident im getting a thoughtful solution. Little more up front effort and less exciting, if blindfold darts and "hope this works" is exciting.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  8. #8
    Join Date
    Apr 2010
    Location
    southern california
    Posts
    535
    Since your attic is already short on ventilation, your best choice would be to insulate below the rafters with foam insulation. Turn your attic space into a non ventilated space and seal the outer envelope.

  9. #9
    Join Date
    Oct 2009
    Location
    Lake Zurich, IL
    Posts
    60
    Quote Originally Posted by tipsrfine View Post
    why do you want to permanently close up the whole house fan? You've indicated you like the way it cools your home on even the hottest days?
    Yes, the whole house fan works great... would never have thought about having one unless the house came with it.

    I'd like to reduce the winter heat loss through the WHF by closing it up. My current thinking is that if I installed an attic fan, it would cool the attic and reduce the summertime radiant heat to the second floor.

    As for sealing the attic deck, that cost to remove/dispose insulation and replace was uneconomical (the cost of a used SUV). Besides, at that point, we were liking the wholehouse fan, so the logic at that time was why bother spend thousands of dollars sealing the attic deck only to leave a big whole in the ceiling where the 40yr old whole house fan was located?

    I don't believe an attic fan is going to suck air from the second floor since I have > 6 sq ft of gable vents that are original to the house like the whole house fan. 6+ sq ft is more than enough for a powered attic fan.

    I understand that line of thinking though... most homes don't have huge gable vents like mine which lead to PAV sucking air through the attic deck and burning PAV motors out after a couple of years.


    Like I said, knowing what I know now, I would have not bought this house.


    I suspect the $99 PAV with thermostat on sale locally is worth the gamble. I can always turn it off or turn up the PAV stat so it goes on very little. I figure a high estimate of 10 hrs/day for 90 days is $0.60 day or about $54 year in electric. If this does work, then the $54 is offset to a small degree by not running the WHF.

    Solar PAV is a good idea... a comparable size solar PAV is $529 -- probably a 7-8 year payback which is what the new Lennox 95% furn payback is after federal rebates and the $2600 credit my wife's employer gave us for putting in a high efficiency furnace and reducing our carbon footprint.


    I'm beginning to think TedKidd's advice was spot on: Get a dartboard.

  10. #10
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    Quote Originally Posted by ChicagoJim View Post
    Yes, the whole house fan works great... would never have thought about having one unless the house came with it.

    I'd like to reduce the winter heat loss through the WHF by closing it up. My current thinking is that if I installed an attic fan, it would cool the attic and reduce the summertime radiant heat to the second floor.

    As for sealing the attic deck, that cost to remove/dispose insulation and replace was uneconomical (the cost of a used SUV). Besides, at that point, we were liking the wholehouse fan, so the logic at that time was why bother spend thousands of dollars sealing the attic deck only to leave a big whole in the ceiling where the 40yr old whole house fan was located?

    I don't believe an attic fan is going to suck air from the second floor since I have > 6 sq ft of gable vents that are original to the house like the whole house fan. 6+ sq ft is more than enough for a powered attic fan.

    I understand that line of thinking though... most homes don't have huge gable vents like mine which lead to PAV sucking air through the attic deck and burning PAV motors out after a couple of years.


    Like I said, knowing what I know now, I would have not bought this house.


    I suspect the $99 PAV with thermostat on sale locally is worth the gamble. I can always turn it off or turn up the PAV stat so it goes on very little. I figure a high estimate of 10 hrs/day for 90 days is $0.60 day or about $54 year in electric. If this does work, then the $54 is offset to a small degree by not running the WHF.

    Solar PAV is a good idea... a comparable size solar PAV is $529 -- probably a 7-8 year payback which is what the new Lennox 95% furn payback is after federal rebates and the $2600 credit my wife's employer gave us for putting in a high efficiency furnace and reducing our carbon footprint.


    I'm beginning to think TedKidd's advice was spot on: Get a dartboard.
    While not specifically condoning the use of a WHF (I'm still researching on that topic) I would say that they do make -or you can make- insulated covers for them so that there is not heat loss through them in winter. Tamarack sells new attic fans that can be installed where your existing WHF is and it has insulated automatic covers that open only when you use it.
    I have to go out right now, but if you would like, maybe I can help you find an economical, yet sound approach, to weatherize your home.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  11. #11
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    Attic deck is not roof deck. Insulating at the roof deck greatly reduces heat gain and heat loss in the attic, essentially turning that space into heated and cooled space comparable to what you have in the house.

    Yes, it's a little pricey. What Ted is saying is to develop a longer term outlook if you plan to stay in that house more than just a few years. 99 bucks seems like an outright steal compared to the used SUV cost for insulation, but what price is your comfort to be at? That attic fan is only useful for a portion of the year, whereas insulation in the right spots and installed correctly works year round without consuming one watt of electricity after installation.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  12. #12
    Join Date
    Oct 2009
    Location
    Lake Zurich, IL
    Posts
    60
    Shophound - Thanks for the reply. I understood your point -- I was just still mulling it over.

    My attic deck comment was in response to Aholleman who recommended sealing the attic floor, not your roof deck comment.

  13. #13
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,763
    Why is it unconditioned attic temperatures that everyone seems to focus on? This is NOT focusing on the problem.

    The problem is perception. You have a lasagna in the oven and it's dinnertime. You don't want to burn your hands taking it to the table. Do you focus on how to get the handles cool enough to touch them?

    NO, YOU FOCUS ON KEEPING "DISTANCE" BETWEEN YOUR HANDS AND THE HEAT! You insulate between the handles and your hands.

    YOU MAKE CONDITIONS SUCH THAT THE TEMPERATURE OF THE HANDLES IS IRRELEVANT. Do this with your house, and surprising problems and comfort issues you didn't associate with your attic "problem" go away also. (Gee mom, lasagna's cold again... etc.)

    This starts by spending time to get a basic picture of building science concepts. Stack effect, reverse stack, airflow for energy replacement, how loads don't always stay evenly distributed... Then you get an audit to understand how these are working in YOUR home.

    So, do you want to continue looking at one aspect of your home as the problem, and try to solve it by cooling the handles on the pan? Or are you ready to look at this as a system of interconnected systems problem? Take a step back and look at the bigger picture?

    Make attic temperatures irrelevant. An audit will help you understand how to bring your whole home into balance.

    To add to SH' post, you don't mull over whether to have surgery before even having diagnostics done. Don't assume you know a cure for a disease you assume you have. Get an audit, understand your home's deficiencies, and what correcting them takes.


    ...or, if you have no care for money, comfort, or our mounting environmental and political troubles around this energy issue, throw spitballs at the wall and hope one sticks. But don't be disappointed when you experience little improvement and higher energy bills.
    Last edited by tedkidd; 05-10-2011 at 12:52 PM. Reason: Internet went down, couple responses jumped in...
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

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