Solar Attic Fans Pull Heat Pressure From Attics

Solar Attic Fans pull Heat from attics. Even in smaller print, everyone will agree to this.

But, how does a Solar Attic Fan pull heat from an attic?  We should look at the fan structure first. 

First, a fan is basically a pump, a pump that just pumps air.  If we had a water pump, we would see the water being drawn in and see the pressurized water exiting the pump outlet. You would clearly be able to see this , water being sucked in, and then being pushed out. What is not so clear to see is the pump increases the pressure as it compresses and then pushes the water out, leaving the pressure lower on the suction side.

That is how a pump works... it does not matter that the material is water or air.  The Solar Attic Fan doing the same thing in your attic. The solar attic fan pulls/pumps air thru the blades and creates a suction vortex behind the fan. The surrounding air now is drawn into the low pressure suction behind the fan, which can also be measured as a low pressure area.

This is why fans work. By creating the low pressure area behind the fan, other air moves in, which is now pushed thru the blades as well. Once the flow is started, the air pressure in the attic is now getting lower than the pressure outside of the attic. Outside air will now be pulled in thru the soffits, keeping the cooler air moving thru the attic.

Without the fan, the heat will increase the pressure in the attic to double or triple outside pressures. At these pressures, the heat will continue to increase, and begin to push straight thru objects in the attic. When the pressure reaches a certain point, the heat will actually penetrate the duct work as well.

It may surprise you to know that the AC unit will product cold air at at least 38-42 degrees. It just depends on the inlet air temperature coming into the unit. But when we measure the duct temp, we find that on average, the temp of the room vent is between 58 and 61 degrees. That is close to a 20 degree loss just in the ducts alone.

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