Attic Fan Negative Pressure

This backdraft can bring dangerous and toxic fumes into your home like carbon monoxide an odorless and deadly gas.

Attic fan negative pressure.

If your home is operating under a negative pressure there s probably a pathway through that exhaust fan duct when the fan isn t running. Simultaneously negative pressure is created in the living area which helps to draw cooler air in through the windows. Due to positive pressure air in the attic is pushed out through the vents or gables. As the air leaves it creates negative pressure behind it sucking in cool air from below into the soffits and creating a self repeating ventilation process.

On the other hand attic fans simply force hot air out of the attic. Fresh air in the home is a good thing. We ve talked about the importance of insulation for an energy efficient home. I have advised him that generally speaking attic fans are a bad idea which he has come to terms with.

Attic fans can create a negative pressure condition in your home causing vented appliances to backdraft. What is negative air pressure. Additional vents are required to draw in fresh air as the hot air is exhausted. However over insulating may restrict fresh air from entering the home.

You also need to think about the openings from dryer vents sewer vents and almost most importantly. Negative air pressure occurs when the pressure inside your home is lower than the pressure outside. The negative pressure created by the attic fan causes carbon monoxide to feed back into your home rather than exhausting up through your chimney. A powered attic ventilator or attic fan is a ventilation fan which regulates the heat level of a building s attic by exhausting hot air.

My father is interested in removing heat from his attic to try to keep the upstairs of his house somewhat cooler. Even if your roof already has ridge vents and plenty of ventilation built in it s a good idea to install gable fans or roof fans to help blow hot humid air out of the attic. However with that understanding that creating negative pressure in the attic can cause all kinds of problems sucking out air from the conditioned space possible back drafting. Attic fans don t provide a cooling relief to the living area.

The point of having an attic fan is to lessen the load on your ac system saving you money. Your chimney and furnace flue vents. A thermostat is used to automatically turn the fan off and on while sometimes a manual switch is used. An attic fan can be gable mounted or roof mounted.

The negative pressure produced by the attic fan is relieved by any opening from the inside of your house to the outside such as opening windows.