During the hot summer months we all start thinking of ways to reduce out electric bills. One of the biggest heat sources in our home is the attic. The attic load is much more than the walls and windows. I see people spending lots of money on new energy efficient windows and not investing in more attic insulation. In our area the Department of Energy recommends between R38 and R49 for the insulation in the attic. That is between 14 to 18 inches thick. This will help reduce the amount of heat that comes down from the hot attic. If you go up in your attic (your favorite place in the summer I am sure) and you can see the ceiling rafters above the insulation then you need more.
But insulation only keeps the attic heat from transferring into our homes, it will also help if we can get the attic cooler. An attic in the afternoon in the summer can be 120 to 140 degrees and some even hotter. Many people think that the way is to add powered attic fans to draw more air through the attic. In most cases this causes more problems than it helps. These powerful exhaust fans actually pull the conditioned air out of the house and into the attic. Yes this cools the attic down, but it actually costs more because you are loosing your conditioned air from the house to the attic. The air you loose to the attic is then drawn into the house from outside which causes your cooling bill to go up.
Another good option for keeping your attic cooler in the summer is Radiant Barrier. This is a coating material that is sprayed on the underside of your roof to reduce the heat that is radiated into your attic. For more info. Radiant Barrier
The “whirly-bird” vents that you see on many homes that spin with the wind to draw air out of the attic are not really made for our area. Once the wind gets over about 8 miles per hour the spinning actually hinders the airflow and decreases the amount of hot attic air that can escape. We very seldom have days that have lower than 8 mph winds. The other problem with these is the bearings go bad and they get very noisy.
The best ventilation is the continuous ridge vent. This is a vent that runs along the entire ridge of the roof. It is at the highest point in the attic so the hot air rises to go out it. You must make sure you have sufficient soffit vents to allow for free airflow. The problem with this is that unless you install it when you are installing a new roof or building your home it is not very practical to retrofit an existing house.
The standard “turtle-back” vents on the roof are the most common and are very effective when enough are installed. They can be added to an existing roof and allow for a lot of airflow when installed properly. They also require that there be enough soffit vents to allow for free airflow.
Another thing to check for is to make sure your vents are not restricted. I have seen many times where the soffit vents are completely plugged up either with insulation that was blown in the attic, or from dirt and rust from the airflow from outside. You need to check yours to make sure they are open and will allow the maximum amount of air to pass through them.
Actually the winter time is the best time to do anything in the attic, that is when it is cooler and almost bearable to be up there. The problem is that we have a tendency to not think about these things until we need them. A little thinking ahead can make the job a lot more bearable.