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Ventilation Systems
Proper house ventilation replaces warm air with cool air, removes
odors and excess moisture, and reduces the level of heat and humidity
in the attic, basement, and crawl spaces.
To help you understand and improve your home's ventilation system,
heating and air conditioner specialists offer you the following information.
There are two types of ventilation:
- Passive ventilators – openings in walls and roof that allow heat to escape
- Mechanical ventilators – include whole-house fans, fans, attic fans, and exhaust fans
Attic Fans
Even though most attics have openings for passive ventilation,
they may still reach 140°F or higher on a hot day. This heat can
seep into living areas below, placing a larger burden on the air
conditioner. With an attic fan (also called a roof fan) you can
substantially reduce the temperature of the attic air.
Although attic fans are smaller than whole-house fans – and
move less air – they are still very effective ways to save
on cooling costs. By expelling hot attic air and pulling in cooler
outside air, an attic fan can reduce attic temperature by 20 percent
or more and room temperatures by as much as 10°F.
An attic fan works this way: a thermostat in the fan itself or
nearby in the attic turns the fan on at a preset temperature and
turns it off when the attic temperature returns to normal. An attic
fan can also be equipped with a humidity control and used during
the winter months to remove excess moisture from the attic, reducing
the possibility that damaging ice dams will form on the roof.
To work correctly, an attic fan should be mounted as high as possible
in a gable or roof surface.
Attic fan upkeep
- Clean and perform maintenance at the beginning of each cooling season.
- Work on the fan from the attic or remove the protective cover
and work on it from the roof.
- Clean the housing and fan blades.
- Clean the screens on the fan and on the attic vents.
- Tighten all screws and bolts, especially the setscrew securing
the blade assembly to the motor shaft.
- Lubricate the motor bearings (unless they're sealed) by pouring
oil in the oil cups.
Exhaust Fans
Installed in a wall or ceiling (or in a range hood), exhaust fans
remove moisture, heat, and odors from kitchens, bathrooms, basements,
and laundry rooms. They also help remove grease particles from kitchens.
How exhaust fans work
- A wall-mounted fan exhausts to the outside.
- A ceiling-mounted fan exhausts into the attic or through a duct
to the outside.
- A fan in a range hood may exhaust through a duct or can recirculate
the air through a charcoal filter without removing heat or moisture.
Caring for exhaust fans
- Once a year: Replace the pellets in a recirculating fan's charcoal filter.
- Once or twice a year: Clean the grill and fan blades.
- Every two months: Wash the grease filter in a range hood fan.
- Every six months: Wash the fan blades and housing.
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