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attic fans

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Ijust had a metal roof installed and i replaced a dura-blend vent system with a whole house fan and my contractor installed it on top of the metal and told me there is no other way to install it ,is this true?
Guest User

10/9/2005
There are many differant types of metal roof systems. Please advise on which type of system,where the fan was located on the roof, the size of the hole for the air and the type of mounting plate/flashing that came with it.
Allan Reid
Dura-Loc Roofing Systems, Inc.

10/12/2005
the roof is rib metal,screw down...the diameter for the whole is 141/2'mounted near the roofline with a aluminum mounting plate model asr-hp.....by airvent
Guest User

10/12/2005
Certainly power vents are not the preferred venting system as they tend to short circuit the are leaving dead zones. Make sure you have eave intake locations. Generally speaking for roof penetrations in vertical rib sheet roofing, one sheet is installed to the top of the hole, then with the hole cut the fan and flashing is installed with a second sheet installed from the centre of the hole to the ridge. Best if it is not located on a side lap. Ther are some surface mounting systems which use two rows of butyl tape sealant along the outside with the screws fastened down through the tape so the self seal. Care must be taken to allow the water from behind the vent to move arond and down with no ponding.
Allan Reid
Dura-Loc Roofing Systems, Inc.

10/13/2005
Here is a picture of the installation .
Guest User

10/14/2005
This is a weak detail and water could puddle behind the vent. Certainly it relies on sealant. I stand by my above comments and certainly a continuous rideg and balanced soffit ventilation works much better and elliminates leak potential.
Allan Reid
Dura-Loc Roofing Systems, Inc.

10/20/2005