Attic Fan Negative Pressure

This can create a potentially hazardous condition.

Attic fan negative pressure.

You also need to think about the openings from dryer vents sewer vents and almost most importantly. Due to positive pressure air in the attic is pushed out through the vents or gables. Additional vents are required to draw in fresh air as the hot air is exhausted. A thermostat is used to automatically turn the fan off and on while sometimes a manual switch is used.

Attic fans can create a negative pressure condition in your home causing vented appliances to backdraft. I have advised him that generally speaking attic fans are a bad idea which he has come to terms with. 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. 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.

This backdraft can bring dangerous and toxic fumes into your home like carbon monoxide an odorless and deadly gas. We ve talked about the importance of insulation for an energy efficient home. On the other hand attic fans simply force hot air out of the attic. 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.

The point of having an attic fan is to lessen the load on your ac system saving you money. 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. Negative air pressure occurs when the pressure inside your home is lower than the pressure outside. What is negative air pressure.

Fresh air in the home is a good thing. 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. However over insulating may restrict fresh air from entering the home. Lloyd your exhaust fan wall cap may well be the entry port for the furnace exhaust.

Windows are not the only openings in your home. My father is interested in removing heat from his attic to try to keep the upstairs of his house somewhat cooler. Simultaneously negative pressure is created in the living area which helps to draw cooler air in through the windows. Your chimney and furnace flue vents.

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.