I am trying to make sure I am understanding the research/studies behind using just the fan to help reduce energy to cool/heat home.

Nest has the option to set a schedule to run the fan in home to circulate the air, or for A/C it has an, "Airwave" option to get the room the thermostat is located to temperature, and then run the fan after to balance out the home temperature. I try to compensate this with balancing the registers in the summer using the dampers.

My HVAC system has an intake inlet on the exterior that almost looks like a bathroom exhaust fan exterior outlet, so it's a good size. My home is a new construction home, built 1.5 yrs ago. The house is sealed up pretty well, so I guess this is to make sure enough fresh air is coming in the home.

Now, will this type of HVAC system have the opposite effect of running just the fan trying to balance the air in the home? I imagine while trying to balance the air and bringing in outside air at the same time, it may just do the opposite and make the temperature go the opposite way even more, respective of what system is running (Furnace/AC).

I have a whole house humidifier that kicks on just the fan when more humidity is needed, but it's hooked up to the hot water line, so maybe that helps balance the temperature difference.

Is the outside air coming in enough to cause the heating/cooling system to kick on more? Or is that air usually minimal? Trying to understand the effects of just running the fan with this type of system has on temperature in the home.


  • It really helps to know what part of the country you live in. I am located in the NW, We use this design scenario to combat what we call sick building syndrome. It is a building code reg that stipulates that because the new homes today are required to be built so tight that a certain number of complete air change are required every 24-hour period. It is not connected to the design of the HVAC system. It is strictly an add-on that happens to use the HVAC system to execute. – Paul Logan Dec 8 '17 at 3:55
  • There is an electrically activated damper in that fresh air line. There also a timer located on the wall somewhere in the house that opens and closed that damper. When the timer activates that damper it also starts the blower assembly in the furnace. It is up to the home owner to decide how many minutes per day to operate the system. – Paul Logan Dec 8 '17 at 3:59
  • @PaulLogan Thanks for the info. I tested mine, when even just the fan is running the damper opens. I know because it is just a simple free hanging door on a pin with an L shaped end that displays where it is at. This one just seems to open mechanically from the suction of the fan regardless of what system is running. – eaglei22 Dec 8 '17 at 12:32
  • If that is true and if you live in a northern climate, I would say the system is inherently flawed. Fresh air is one thing. That is ridiculous. I would be stuffing that duct with fiberglass insulation. – Paul Logan Dec 9 '17 at 4:47

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