Here’s how you can ensure your attic has proper ventilation
If you are looking for ways to reduce heat in your home by adding insulation, a radiant barrier or fans, hold off – there’s a better way.
Homeowners tend to think that by cooling down the attic, the whole house will become cooler, therefore requiring the air conditioner to run less, resulting in lower utility bills. Sounds good in theory.
In reality, they will be throwing away thousands of dollars in a misdirected effort to save electricity and reduce their bill.
The heat in the attic only affects 10% of the air conditioning bill in one month. Homeowners will never achieve a return on investment by adding thousands of dollars for remedies that will not work.
Assuming the attic is properly insulated to an R-38 and properly ventilated, there is nothing more economical to be done to the attic. Leave the attic alone.
An attic fan, be it solar or electric powered, creates a negative pressure in the attic. Power fans draw air through the attic by creating an airflow. They are effective yet don’t allow natural forces to ventilate the attic. Plus, it’s somewhat expensive to buy and install.
Operating power fans costs more than the fan’s benefit. Even fans that automatically turn on and off at selected temperatures are not worth the investment because the summer heat in the attic will cause the fan to run almost continually. So, what you are really will doing is increasing your demand for air conditioning.
There’s a better way – proper passive ventilation and properly installed R 38 insulation.
There are different kinds of vents to consider:
Louvers are covered openings that allow air to escape the attic. They are located on the gable (nonload-bearing) ends of the house and allow limited airflow. This system relies on wind direction to create airflow through the attic. When the wind blows perpendicular to the ridge, it circulates air around the louver, which acts as its own intake and exhaust vent. If the wind blows parallel to the ridge, the airflow pattern acts as a draft that moves in one louver and out the other.
These are a very common form of passive attic ventilation in Arizona. Dormer roof vents allow heat to escape from the vent itself and are important to properly cool attic space.
Ridge vents are mounted along the top of the ridge of the roof. They provide even and consistent exhaust ventilation. It is best to run a ridge vent the entire length of the attic. Caution: Some roofers cut costs by running only the length required by code. Rosie recommends running the vent from roof end to roof end for best results. A ridge vent won’t work well alone; adequate intake ventilation must accompany the ridge vents in order to maintain airflow.
A common method of ventilation, soffit vents, are located under the eaves, where they will have minimal exposure to rain and other weather conditions. Soffit vents on each side of the structure create equal ventilation on both sides. Soffit vents should not be your home’s only vents, though.
If they are, the air movement is restricted to the attic floor, and airflow does not pass over the roof sheathing. These vents are how your attic inhales the air it needs to exhale through the passive exhaust system you choose; louver, ridge, dormer, or turbine vents.
Also called whirly birds, turbine vents are wheels mounted near the ridge of the roof. They are usually installed two or three per roof. Most of the time, they act as exhaust vents, but air also can enter the attic through a turbine. Turbine vents are not a good option because they only exhaust small portions of the roof and allow rain to enter the attic.
Rosie’s Recommendation: Ridge vents accompanied with soffit vents will create the most effective attic ventilation for your home. The combined system will draw air from the soffits along the sheathing and exhaust it through the ridge vent.
Join Rosie on the House every Saturday morning from 8 a.m. to 11 a.m. on KTAR News 92.3 FM. If you’d like to send us questions or comments, email mailto:[email protected] Follow us on Twitter and “Like” us on Facebook. For more do-it-yourself tips, go to rosieonthehouse.com. An Arizona home building and remodeling industry expert since 1988, Rosie Romero is the host of the syndicated Saturday morning Rosie on the House radio program. Call 888-767-4348 with questions and comments.