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MN Renovator · 06-21-12, 05:18 PM

That's a gable fan and isn't designed to be installed as a whole house fan. Whole house fans are different because they are designed to be installed on the ceiling and have louvers that shut when the fan is off to block air from rising to the attic when its off. Cheap ones don't shut and seal that well and aren't insulated. Ones that IMHO you really need to avoid having a sieve installed on your ceiling that lets air flow, especially warm air leaving the house in the winter are well sealed and have insulated panels that shut over the unit, or something similar to that, when its off. Those gable fans will not flow that much CFM if you are putting any type of resistance against their air flow, the CFM is essentially free flow CFM assuming that there is a good opening inlet that isn't restrictive. Attaching ductwork to these will cut your CFM and likely also raise the energy usage at the same time.

Good whole house fans that will actually save you money are expensive. Since getting a good insulated one that seals well are not cheap, I just went with using 4 box fans off of a guy on Craigslist for dirt cheap. I open the lower level window with two box fans blowing in on the downstairs shady side of the house and two open on the shady side upstairs and open the hot/sunny side upstairs window. This way you get the cooler air from downstairs replaced and pushed upstairs while being replenished with cool air and you get the full crossflow upstairs. Depending on your house configuration this might bring good airflow throughout your house, it works very well for mine. FYI, Newer Lasko and pretty much any other 20" box fan use about 100 watts at full speed. I disassembled one and was surprised to find that they are actually PSC motors now, which is more efficient than the shaded pole motor that I would expect in a cheap fan. I've tried just cross-flowing the upstairs but it didn't work as well and getting the entire house to move air. It might be more efficient to move air with two fans with one in each of the windows instead of two in each window but for me that means I need to put up plastic to prevent the air from backflowing out instead of turning the house into a duct.

The reason I'm suggesting this is that I had a whole house fan in the house I grew up in and two box fans pulling air into a room with an open door will move about the same amount of air through an open doorway as a whole house fan does, without the expense of getting one that won't cost you more in infiltration and lack of insulation.

06-21-12, 05:18 PM	#2
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	That's a gable fan and isn't designed to be installed as a whole house fan. Whole house fans are different because they are designed to be installed on the ceiling and have louvers that shut when the fan is off to block air from rising to the attic when its off. Cheap ones don't shut and seal that well and aren't insulated. Ones that IMHO you really need to avoid having a sieve installed on your ceiling that lets air flow, especially warm air leaving the house in the winter are well sealed and have insulated panels that shut over the unit, or something similar to that, when its off. Those gable fans will not flow that much CFM if you are putting any type of resistance against their air flow, the CFM is essentially free flow CFM assuming that there is a good opening inlet that isn't restrictive. Attaching ductwork to these will cut your CFM and likely also raise the energy usage at the same time. Good whole house fans that will actually save you money are expensive. Since getting a good insulated one that seals well are not cheap, I just went with using 4 box fans off of a guy on Craigslist for dirt cheap. I open the lower level window with two box fans blowing in on the downstairs shady side of the house and two open on the shady side upstairs and open the hot/sunny side upstairs window. This way you get the cooler air from downstairs replaced and pushed upstairs while being replenished with cool air and you get the full crossflow upstairs. Depending on your house configuration this might bring good airflow throughout your house, it works very well for mine. FYI, Newer Lasko and pretty much any other 20" box fan use about 100 watts at full speed. I disassembled one and was surprised to find that they are actually PSC motors now, which is more efficient than the shaded pole motor that I would expect in a cheap fan. I've tried just cross-flowing the upstairs but it didn't work as well and getting the entire house to move air. It might be more efficient to move air with two fans with one in each of the windows instead of two in each window but for me that means I need to put up plastic to prevent the air from backflowing out instead of turning the house into a duct. The reason I'm suggesting this is that I had a whole house fan in the house I grew up in and two box fans pulling air into a room with an open door will move about the same amount of air through an open doorway as a whole house fan does, without the expense of getting one that won't cost you more in infiltration and lack of insulation.