house vent | Insulation/Energy/Building Envelope Q&A | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

Q&A Forums

Author	Comments
jay cronin Posted: Sep 14, 2008 03:27 PM	house vent I built a house for a customer and the whole house has open cell foam insulation. They want to install a house fan so the don't use the a/c as much. Foam is in the rafters. any ideas how to do this?
Jim Coler Posted: Sep 14, 2008 06:43 PM	This can be done the same way you would with a normal whole house fan, except in the winter time, you want to have a sealed and insulated cover for the fan hole. You can put the fan through the roof or through the side gable end wall - which ever is more convenient. The gable end wall might be more efficient since you won't have summer roof heat potentially coming back into through the hole. Theoretically, this would not happen since warm air rises, but different wind currents may contribute to it. Again, just plan ahead on how you plan to seal it up and insulate it in the winter. You should also use an automatic opener for the vent louvers to minimize the warm air that gets drawn in during the daytime. Just keep in mind that as you cut a hole in the attic (wall or roof) you open up the risk of increasing the air movement through the house if you can't seal it sufficiently.
Rob Granger Posted: Sep 14, 2008 08:42 PM	jjmelt, Why did the homeonwers want a house with spray foam insulation if they are just going to go backwards by putting a whole house fan in? The house is going to be very efficiently heated or cooled because of the spray foam, therefore the cost to cool same will be minmal. I am against the thought of putting in a whole house fan. Besides the above arguement, I have yet to see a fan unit that seals well so air will infiltrate whether in the summer or winter. Also bringing in fresh air on such a level will also bring in pollens and pollutants. Look at all sides carefully before you decide. Good Luck....
jay cronin Posted: Sep 14, 2008 08:56 PM	thanks for the reply The reason i didn't do it when I built the house is because i couldn't find a fan that would seal up tight. I have used a fan that seals nice on other houses but couldn't figure a way to get it vented outside without comprimising the tightness of the house. They would like to only use the fan when its not that hot. The fan is cheaper to run then the a/c
William Gibson Posted: Sep 17, 2008 06:58 AM	I'd try and deter them away from the idea of a whole house fan. There is nothing good about the units except the thought of saving electricity in the summer time. You also need to think of the fact that the whole house fan can also draw CO up through the home from combustion appliances in the basement.
Jim Coler Posted: Sep 18, 2008 07:41 AM	My suggestion would be to have them put a big fan in a second floor window in the evening and nighttime with windows downstairs open to pull in the cool air and exhaust the warmer air from the daytime. Another option would be geothermal heating system which is 300-500% efficient and is like free AC. The downfall here is the upfront cost.

Author

Comments

jay cronin

Posted: Sep 14, 2008 03:27 PM

house vent

I built a house for a customer and the whole house has open cell foam insulation. They want to install a house fan so the don't use the a/c as much. Foam is in the rafters. any ideas how to do this?

Jim Coler

Posted: Sep 14, 2008 06:43 PM

This can be done the same way you would with a normal whole house fan, except in the winter time, you want to have a sealed and insulated cover for the fan hole. You can put the fan through the roof or through the side gable end wall - which ever is more convenient. The gable end wall might be more efficient since you won't have summer roof heat potentially coming back into through the hole. Theoretically, this would not happen since warm air rises, but different wind currents may contribute to it. Again, just plan ahead on how you plan to seal it up and insulate it in the winter. You should also use an automatic opener for the vent louvers to minimize the warm air that gets drawn in during the daytime.

Just keep in mind that as you cut a hole in the attic (wall or roof) you open up the risk of increasing the air movement through the house if you can't seal it sufficiently.

Rob Granger

Posted: Sep 14, 2008 08:42 PM

jjmelt,
Why did the homeonwers want a house with spray foam insulation if they are just going to go backwards by putting a whole house fan in? The house is going to be very efficiently heated or cooled because of the spray foam, therefore the cost to cool same will be minmal. I am against the thought of putting in a whole house fan. Besides the above arguement, I have yet to see a fan unit that seals well so air will infiltrate whether in the summer or winter. Also bringing in fresh air on such a level will also bring in pollens and pollutants. Look at all sides carefully before you decide. Good Luck....

jay cronin

Posted: Sep 14, 2008 08:56 PM

thanks for the reply
The reason i didn't do it when I built the house is because i couldn't find a fan that would seal up tight. I have used a fan that seals nice on other houses but couldn't figure a way to get it vented outside without comprimising the tightness of the house.
They would like to only use the fan when its not that hot. The fan is cheaper to run then the a/c

William Gibson

Posted: Sep 17, 2008 06:58 AM

I'd try and deter them away from the idea of a whole house fan. There is nothing good about the units except the thought of saving electricity in the summer time.

You also need to think of the fact that the whole house fan can also draw CO up through the home from combustion appliances in the basement.

Jim Coler

Posted: Sep 18, 2008 07:41 AM

My suggestion would be to have them put a big fan in a second floor window in the evening and nighttime with windows downstairs open to pull in the cool air and exhaust the warmer air from the daytime.

Another option would be geothermal heating system which is 300-500% efficient and is like free AC. The downfall here is the upfront cost.

You need to login to reply to this topic. Please click here to login.