The Importance of Attic Ventilation

A properly vented attic can save you money-and add life to your new roof.

BY TED MICHELSEN

An extremely important but often misunderstood part of good home design is attic ventilation. Proper attic ventilation can save homeowners energy, extend the life of their roofing materials and reduce moisture problems like mold, mildew and some other types of water damage.

Since 1942, the Federal Housing Administration (FHA) has had minimum attic ventilation requirements, and the building codes have included attic ventilation for almost as long.

So why do we even need to worry about attic ventilation?

Unfortunately, some homebuilders have promoted non-ventilated attics to save pennies.

RSI Magazine's 2005 State of the Industry Report shows that 90% of residential roofing contractors say that they check attic ventilation before reroofing. And when they do, 56% say the existing attic ventilation is inadequate.

So, if you're currently contemplating a new roof, there is a greater than 50% chance that your attic is poorly ventilated. This wastes money, energy, and can lead to premature roof failure, water damage and possibly, mold growth.

Why ventilate?

By ventilating the attic space we accomplish two things. Once, we move hot air out of the attic during the summer (temperatures up to 160 degress F) and keep the attic temperature down (105 degrees F), which will extend the life of roofing materials and keep the house cooler. Two, we move moisture that has come from inside the house out of the attic before it can condense, cause mold or other damage.....

Summer months

During the summer, we have high air temperatures and long hours of sunlight, which causes the roof surface to become hot. This heat is then transferred to the attic. If the attic is not ventilated the attic temperature can easily reach 160 degrees F, while a properly vented attic will reach about 105 degress F.

Even with insulation, the heat in the attic will flow down into the house, because heat does not follow gravity but rather flows from hot locations to colder locations. The rate of heat flow is related to the temperature difference. Thus if the house temperature was 80 degrees F, a vented attic would only move about 1/3 the amount of heat into the house as a non-vented attic. For example, a 2,000 square foot house in Phoenix, AZ could save about $125 per year in energy costs between a vented and non-vented attic.

Added to the increased energy cost is shortened life of the air conditioner unit due to additional operational hours.

The added heat in the non-vented attic will cause the roofing materials to get hotter as well. Heat causes increased aging rates for organic materials like wood and asphalt, thus shorting their life. This problem is well recognized by the asphalt shingle industry, and many manufacturers do not cover shingle damage due to non-vented attics in their warranties.....

Fixing ventilation issues

If your house does not have any ventilation, it can be added relatively easily. First, install the appropriate amount of soffit venting for your house. Make sure that the attic insultion does not block the airflow of the soffit vent. Since installing ridge vents or static vents require major roofing work, which sould be done by a roofing professional, it may be easier to install a powered vent near the ridge, as typically only one hole is needed.

If you are experiencing some of the problems discussed above and you have attic vents, it is possible that the attic insulation was incorrectly installed so that it either covers the soffit vents or blocks the air flow from the soffit vent to the attic.

If this is the case, removing or pulling back the insulation from the eave and soffit areas will solve the problem. Either, the homeowner or a professional insulation contractor can do this work.

There are cardboard or foam attic rafter vents that fit between the rafters and prevent the insulation from blocking the air flow from the soffit vents.

In summary, attic ventilation is important for a long lasting house in the U.S., especially when air conditioning is used.