It is estimated that 9 out of 10 homes in North America do not have proper attic ventilation. In the summer,
an improperly ventilated attic can cause heat to build in excess of 160°F. This superheated air eventually
penetrates the ceiling insulation into the living area below.
Types of damage that can result include:
A properly ventilated attic can help reduce the load on your air conditioner by moving
- Premature aging of your roofing system (“fried” shingles)
- Warping, cracking, or breaking down of wood framing
- Damage to siding, exterior or interior paint, and wallpaper
- Higher energy costs
the superheated air out of your attic before it builds up and causes damage.
In the winter, various household appliances, bathtubs, showers, and cooking vapors can contribute to
excess moisture build-up. Improperly ventilated attics will allow this moisture to collect and cling to the
underside of the roof. There, it will condense and fall, soaking the attic insulation and reducing its efficiency.
Additional structural damage can include:
- Roof deck warping and rotting of the wood frame
- Mildew growth
- Buckling of shingles and felt
Proper Attic Ventilation systems allow a continuous flow of outside air through the attic, protecting the
efficiency of the insulation and helping to lower temperatures in the living space. It consists of a balance
between air intake (at your eaves or soffits) and air exhaust (at or near your roof ridge). The FHA (Federal
Housing Administration) recommends a minimum of at least 1 square foot of attic ventilation (both intake and
exhaust) for every 300 square feet of attic space. This amount is generally divided equally between intake
and exhaust ventilation to insure proper air flow through the attic.
Calculating Your Ventilation Requirements:
Remember: Always have a balanced ventilation system. In no case should the amount of exhaust ventilation
- Step 1: Calculate attic square footage
- Step 2: Calculate NFA (Net Free Area) needed by using by dividing attic square footage by 300
- Step 3: Split the amount of NFA needed equally between the intake and the exhaust
- Step 4: Calculate # of vents by dividing by area of vent (ie: (the SSB960 has 60 square inches of NFA)
exceed the amount of intake ventilation.
Note that in municipalities such as Laguna Beach, that are considered Fire Zones, soffit venting is not
allowed. As such, the intake and exhaust must both be on the roof; one is simply higher and the other lower
on the roof.