Balanced Attic Ventilation

The unbalanced attic consisted of a mix of ridge vents and electric power fans without intake ventilation.

Balanced attic ventilation. The balanced approach helps to optimize air exchange between the attic and the outdoors and allows for effective management of temperature and moisture inside the attic. Figure courtesy of the nrca. Another way to get balanced ventilation is to use the exhaust fans with controls and also install a supply fan. Figure 1 a balanced system.

Balance is the key. You can do this with a bath fan installed to blow air into the home or you can use a fan made specially for this task. In cold weather ventilation helps remove moist air from the attic that has migrated from the occupied living space reducing the risk of condensation in the attic. An under roof cathedral ceiling or attic ventilation system to help the building in any way needs to be properly designed and installed with adequate intake venting at the eaves outlet venting at the ridge and with careful sealing of air leaks from the occupied space into the attic or roof cavity to avoid heat losses or increases in both moisture movement into the roof cavity and increased heating or cooling costs.

That said air resistance and interference such as vent grates reduces the area of true ventilation. Several purposes of an attic ventilation system are to provide added comfort to help protect against damage to materials and structure and to help reduce energy consumption during all four seasons of the year. In other words the entire vent opening doesn t count as vented space. Determine net free ventilating area nfva sq.

The most common method is the static method. They have two basic models. Calculations for a balanced ventilation system for proper ventilation the amount of under eave or soffit ventilation must equal or be greater than the amount of ventilation at the ridge. The importance of balanced attic ventilation improved ventilation can enhance your roof s performance and your home s air quality many homeowners overlook the importance of proper ventilation when constructing a roof or overseeing a roof repair.

This method relies on convection which is a mode of heat transfer that is caused by the tendency of warmer air to rise. Of attic floor space required minimum square feet ft of nfva 300 ft ft required nfva 300. There are two methods used to ventilate attics. The balanced attic consisted of electric power fans repositioned for maximum efficiency and air vent s new edge vent a shingle over intake vent.