Building Science Attic Ventilation

The amount of cooling provided by a well ventilated roof exposed to the sun is very small.

Building science attic ventilation.

Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. Intake vents located at the lowest part of the roof under the eaves allow cool. In modern home construction attic ventilation is used to improve indoor air quality increase energy efficiency through natural cooling and prolong the life of building materials through moisture management. Air from the house would exit the top of the house enter the attic and be removed from the attic by thermal buoyancy and wind.

Code requirements the international building code. And because vented attics aren t insulated they get very hot in summer and very cold in winter. In mixed climates ventilation serves either role depending on the season. Lowering the temperature in the attic can help reduce air conditioning energy costs and roof deck temperature optimize the service life of a roof covering and minimize ice damming.

There s been so much stuff said about roofs that you sometimes lose perspective. Typically building codes include minimum requirements applicable to attic ventilation. In a hot climate the primary purpose of ventilation is to expel solar heated hot air from the attic or roof to reduce the building s cooling load and to relieve the strain on air conditioning systems. Proper attic ventilation can be an impor tant performance consideration when design ing and installing steep slope roof systems.

The roofing industry also has practical guide lines for attic ventilation. By creating a path for air to move structural vents are supposed to prevent the buildup of moisture in an attic. In hot climates the primary purpose of attic or roof ventilation is to expel solar heated hot air from the attic to lessen the building cooling load. Purchase ventilation books covering related topics such as indoor air quality mechanical ventilation written to help contractors with their building process.

But a vocal group of building scientists says that in hot and humid climates vents will likely draw moisture into the house. Joseph lstiburek talks about the not so controversial ways to maximize the efficiency and airflow of your roof and attic.