The attic, which is the part of the house that is directly under the roof, needs to be well ventilated with attic exhaust fans.

Since most attics are usually smaller enclosed spaces, unventilated attics are unsafe because pathogens in the air and harmful gases can be easily inhaled by the family members.  The attic in summer will also be very hot because it is directly under the roof.

To select an attic exhaust fan, the volume of the attic should to be determined so that the Cubic Feet per Minute (CFM) of the attic exhaust fan can be calculated.  The volume can be calculated by multiplying the length, width and height of the attic.  The volume is then divided by the value of Air Changes Per Hour (ACH).  The Home Ventilating Institute (HVI) recommends the value of 6 for attics.  Hence, if the volume of the attic is 2250 cubic feet, the attic exhaust fan should have a CFM of 375 or more.  But there is another consideration in attic exhaust fan choice – the roof type.  Roofing materials can store or emit varying degrees of heat.  The information about the roof type can be secured from the manufacturer.

It is also important to consider the static pressure brought about by the attic exhaust fan.  This can be calculated easily.  It is recommended that screw be used instead of nails because of the exhaust fan’s vibrations.

Installing an attic exhaust fan is easy and can be a do-it-yourself.  If the manuals are not clear, there are many resources on the internet for safe installation.