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  1. #1
    Join Date
    Apr 2001
    Posts
    52
    a few years back a roofer installed what I think is called an attic ventilator...motorized fan on roof that operates off thermostat. (I think he replaced a turbine that wasn't motorized but moved when the wind blew.)
    Now the motor had died.
    Should I replace this?
    I have read that sometimes these can create negative pressure in the house. I've also read that they don't help lower the temperature in the attic. Sorry if this isn't an HVAC question.
    Thanks.

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    U of Florida Studty determined ,at best you spend what it saves in operating it.

    Replace with a turbine ,or ignore .Next roof replacement,install ridge vent.

  3. #3
    Join Date
    Apr 2001
    Posts
    52
    Thanks very much.

  4. #4
    Join Date
    Apr 2001
    Posts
    52
    Do you recommend a particular turbine? Is the Attic Aire model by AirVent a reasonable one to use? Thanks

  5. #5
    Join Date
    Jun 2004
    Location
    Dallas
    Posts
    179
    IT depends on where you live and other factors.

    In Dallas, I had the static-type roof vents and I could NOT keep my house below 80 degrees in July and August running constantly. This was not a matter of efficiency, it was a matter of livability and sanity.

    I put in an electric roof vent and made sure that I had the required number of soffit vents to allow enough outside air into the attic so I would not have the negative pressure situation you mention.

    The vent plus solar screens cut my bill by more than 50% the next year. I really couldn't beleive how much it dropped. I was able to keep the house at a comfortable 77 degrees with normal cycling.

    Some people do it to increase efficiency, and then it is a toss-up, but some do it out of necessity. Just make sure you have adequate attic intake air.

  6. #6
    Join Date
    Apr 2001
    Posts
    52
    Thanks,
    I live in Houston so it's hot and humid. I don't know whether we have sufficient attic intake vents ). I'll try to check on that. We are able to keep the house cool enough, the plastic film on the windows helps a lot I think.
    It's just real hot in the attic.

  7. #7
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    ridge vents should NOT be installed on low sloping roofs -- water may be blown in!

    read info @ BUILDINGSCIENCE.com

    check your vent inlet screening -- regular window screen clogs fast with lint -- use 0.25 inch hardware cloth to keep out insects -- then overlay that with 0.5 inch to keep out squirrels --

    I reworked my bdrm attic pwr vent to be cord plug into elec outlet box, so can remove motor from roof -- which I just did to oil motor bearings last week after 5yr service. Unit is probably 20+yr old -- does good job.

    BTW the cheap units have flimsy fan blades & motor brackets -- I gave up after two for my attic over kit.



    [Edited by cem-bsee on 06-03-2005 at 03:38 PM]

  8. #8
    Join Date
    Jul 2004
    Posts
    253
    Originally posted by old yeller
    IT depends on where you live and other factors.

    In Dallas, I had the static-type roof vents and I could NOT keep my house below 80 degrees in July and August running constantly. This was not a matter of efficiency, it was a matter of livability and sanity.

    I put in an electric roof vent and made sure that I had the required number of soffit vents to allow enough outside air into the attic so I would not have the negative pressure situation you mention.

    The vent plus solar screens cut my bill by more than 50% the next year. I really couldn't beleive how much it dropped. I was able to keep the house at a comfortable 77 degrees with normal cycling.

    Some people do it to increase efficiency, and then it is a toss-up, but some do it out of necessity. Just make sure you have adequate attic intake air.
    Did you add the roof vent and solar screens at the same time? If so, then you dont know which one had the biggest impact?

  9. #9
    Join Date
    Aug 2003
    Posts
    626
    OldYeller--no matter how much sq. area of soffit/gable vents you have, you will still have a negative pressure in the attic. This will still pull airconditioned air from room below. Power vents don't save energy or lower cooling bills.

  10. #10
    Join Date
    Oct 2004
    Posts
    76
    Hi eve,

    I thought I'd add my input in the hopes that you might find it useful since I went through this exact same thing 1 month ago and live in the north TX area.

    I have 3 turbines on my house. I considered replacing all of them with solar powered attic fans. These types of fans are totally enclosed and the solar panel is what powers the fan, so there is no need to wire into your electrical system. Sounds great, but 2 big drawbacks for me:

    1. The cost per fan was at least $300!!
    2. Like you indicated, there is the possibility of the motor crapping out in a few years. What then? Buy another one? Shell out another $300??

    No thanks.

    I ultimately decided to simply replace the turbine with new ones. My old ones were at least 30 years old, made of galvanized steel, and those things weighed at least 7 pounds! They would only turn if the wind was around 15MPH. Absolutely terrible, plus they were rusted.


    When you replace yours, purchase aluminum turbines only. There are a couple of big reasons for this.

    1. Aluminum will not rust.
    2. Aluminum is much lighter than steel.
    3 Being that aluminum is lighter, the turbine will turn more often.
    4. Aluminum is generally a little cheaper.

    Attic Aire or Ventmatic are both good companies, but don't buy steel turbines. Place a special order if you have to but just make sure they are aluminum. My turbines now spin if there is just 2MPH worth of wind...they spin all the time now.

  11. #11
    Join Date
    Jun 2004
    Location
    Dallas
    Posts
    179
    Originally posted by tuccillo


    Did you add the roof vent and solar screens at the same time? If so, then you dont know which one had the biggest impact?

    OldYeller--no matter how much sq. area of soffit/gable vents you have, you will still have a negative pressure in the attic. This will still pull airconditioned air from room below. Power vents don't save energy or lower cooling bills.
    True, I don't know exactly what worked better- but I would still recommend them both in the right situation. I only had 5 west-facing windows in the whole house.

    Uktra- If you want to get picky, of course there is negatve pressure! There is always negative pressure whether it is from static vents, whirly-birds, or power vents. You will even have it from nothing more than a stack effect in the attic.

    You are obviously speaking your opinion regarding a different situation than the one I mentioned (did you read it?) I am speaking from PROOF and direct EXPERIENCE. I don't feel like digging up my 4 year old electric bills to show you my bills going from 275 in august to 135 in August the next year. Like I said, the house could not go below 80 degrees before, would stay comfortable at 77 with the attic fan afterwards. The solar screens helped, but I always had my blinds closed anyways. The attic temps went from 150+ to around 110.

    Now, if you would like to discuss an already optimal situation where someone wants to shave a few dollars off their already moderate cooling bill, I'm sure you are correct. But in my particular situation- you are wrong.

  12. #12
    Join Date
    Aug 2003
    Posts
    626
    Old Yeller--Unless you had an individual meter for your A/C, and you compute the average temps form one year to the next, bills going down don't mean the power vent saved you money. There were are too many other factors involved. So you can believe I am wrong but before you give advise to people,you had better have some research to back it up--which you don't.

  13. #13
    Join Date
    Apr 2001
    Posts
    52
    thanks everyone for your thoughts on this.

    thanks txnoob,
    regarding aluminum:
    someone on HVAC talk mentioned a company called LOMANCO
    http://www.lomanco.com/ProductPAGES/BEBBIB.html
    they're aluminum, and seem okay from their description.
    anyone have any experience with these?

    I put a thermostat in my attic today and if it was accurate it read 104 degrees F
    that seems okay
    but surely, as we approach August in Houston, that will go up perhaps up a lot.
    so
    perhaps it makes sense to get the turbine which I think means no electric power, just self propelled.
    That sounds great txnoob to have turbines that turn with just a 2 mph wind.

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