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Attic Roof Fans

Attic Roof Fans

Click here if your attic roof fan no longer works.

First, some definitions:

  • Attic Roof fan:  Installed in the roof itself.  From the outside, it looks something like a mushroom.  Operates with an automatic thermostat.  It pulls outside air in through the gable vents, and any soffit vents or passive vents if they exist. 

  • Gable fan: Fan installed inside the attic against a gable vent at the side of the attic and operates with a thermostat.  Since you can only pull air through one vent, it isn't as big or able to do as much as a roof fan..

  • Whole house fan:  Large fan (48" in diameter) which pulls air through the house via open windows.  This has large louvers (48" x 48") in the ceiling of a hallway on the upper floor.  Operated with a switch.   These can't be used when you are using air conditioning.

From mid-spring until early fall, the sun beats down on the roof top and heats up the attic space.  It can get up to 130° F.  If this hot air is not cleared out, it will slowly saturate the beams, insulation, ceilings and walls. The large mass of hot air and the heated wood, insulation and sheet rock slowly transfers this heat to the top floor (or main floor of a ranch style house).  This is why the outside can be cooling off in the afternoon/evening but the house is still getting hotter and hotter inside.

The solution is to get rid of this high volume of hot air.  With a typical thermostat setting of 110° F, the roof fan turns on, pulls out the hot air out, replacing it with cooler air being pulled in through the vents.  A roof fan can pull air through the 2 gable vents and/or soffit vents on the roof overhang.  Even if it's 90° outside, that's a lot cooler than the 130° attic air.

Click here to see some photos of an attic roof fan installation.

Helpful hints:

  • A roof fan can only pull hot air out if there are vents to allow cooler air to be pulled in to replace it.  Proper ventilation is important.

  • A gable fan is usually much smaller since it can only pull from the one other vent.  It can only move 1/2 the amount air.

  • You want a high quality roof fan.  It will work hard, in hot temperatures and needs to be big enough to do the job.

    • There are some cheap roof fans that only last a few years.

    • A metal dome holds up better to weather, wind and ulta-violet rays far better than a plastic dome.

    • It can cost as much to replace a fan as to install one brand new.

    • Each year, we replace many other fan brands.  Some fans and models have longer warranties than others.

    • Larger homes with large volume attics (steep roofs) should have a larger roof fan.

  • Occasionally, a house can't use a roof fan.  Usually this is in expanded Cape Cod or certain contemporary homes where there is no significant attic air space to vent out.

Already have a fan?  If your attic fan has stopped working, it's either the motor or the thermostat; we can't know until we see it.  However, we can give an estimate for the following scenarios:

    1. Bad thermostat:   $265 to replace + tax

    2. Bad motor: if a replacement motor is available, $475 + tax to replace 

    3. Bad unit (motor, brackets, etc)  Replace the entire unit with a new fan with automatic thermostat and master Off-switch: $875 - $1175 depending on the size of the fan.

Note:  Replacements are taxable repairs, new installations are capital improvements which are not taxable.

Type of attic/house



Flow Capacity

Attic square footage

Regular attic of older homes  (pre-1985)


5 years material
3 years labor

1250 CFM

1400-1800 Square Feet

Large, high volume attics of newer homes with steep roofs


10 years material
5 years labor

1530 CFM

up to  2200 Square Feet

Give us a call or send an email so we can get things back working as soon as possible.