Attic Fan Installation -- remove bug screen?

Question

Hi,

I plan to install an attic fan in the gable of my roof. Currently there is a screen on the gable vent to keep bugs/bird/bats out I assume. Can I have the fan blow through the screen or do I need to remove the screen? If I do remove it, how do I keep out bugs/birds/bats?

Thanks!

Answer 1

I would suggest putting some automatic louvers in place of the gable vent.  This way the louvers open when the fan comes on and shut when the fan goes off.  The bugs won't come through the fan.  Box the fan in so the air does not blow back in the attic.

Dave

Answer 2

You can leave the screen in place; it's not going to affect the air circulation.

Have you considered a solar roof top fan. They work much better; are more efficient and you completely reduce the chance for an attic fire.

It's a bit more involved then just hooking up a gable fan but in the long run (and short run) it will work much better.  It's a steep upfront cost but the solar is going to give you the best results.

Answer 3

leave the screen, the fan will work fine

Answer 4

While "gable" fans are cheap and easy to pick up they don't always fit the triangle shape of the existing fixed louvers backed by a screen to keep the bugs out of your attic.  You will necessarily be doing some reshaping of the opening to eliminate blowback (air coming back around the fan)  In installations I typically had to create a box that the fan (round) mounted into that then attached to the different shape of the gable end (triangle).  The final opening (sq in or sq cm.)must be greator than the opening of the fan.(pi x r sq. in in. or cm.) This increase is to make up for the drag of the screen and the usual fixed exterior louvers.

You can't eliminate the screen because you will get animals coming in when the fan is off.  If the screen is clean it is not a problem.  When installing fans like this I have always mounted them on a board and put the board on hinges.  After the fan is operated for a season the screen will begin to plug up with lint, insulation, dust or dirt.  The available open space will become increasingly restricted and the screen will have to be cleaned.  The hinges make that easy. (simply screwed shut at the other end)

Roof mounted exhaust fans require less work to install properly, have a bigger spaced screen on them, but are installed from the outside (on the roof).

Remember that the fan is only a part of the ventilation "system."  Adaquate incoming air (free air) must be provided for and what is usually available is severely inadaquate.  Look on the box that came with your fan for required incoming air.  

In one case, to provide adaquate incoming air I purchased two gable fans (so the cfm was matched) and reversed one to blow the air in.  To keep bugs and weather out I had to also install a motorized damper (outside of the incoming air fan.)  Both fans (and the motorized damper) were turned on by the same attic thermostat.  This system was very good at keeping the attic cool where I could not make a big enough opening for adaquate free air.  (slate roof and no soffits)

Answer 5

It's been a few years since I worked with attic fans but first I would consult the manufacturers instillation instructions. If the instructions do not specify I would be left to believe that the screen would not cause any problems. If you are still concerned you could install a somewhat coarser screen. Unless the manufacturer instructs you ro remove the screen I would leave it!