Northern Climate Roof Venting

These vents are static vents that are placed over holes in the roof close to the roof ridge.

Northern climate roof venting.

The minimum venting is one square meter of screened ventilation hole to every 150 square meters of floor space or one square foot per 150 square feet. In cold climates this is an advantage. Our field measurements and computer modeling show that without attic venting the temperature of the underside of the roof sheathing increases by 10 f 20 f. In a cold climate the primary purpose of ventilation is to maintain a cold roof temperature to avoid ice dams created by melting snow and to vent any moisture that moves from the conditioned living space to the attic.

Warming up to unvented roofs the underside of the roof sheathing is where the real benefits of not venting roof assemblies are found. But beyond that they make it easy for snow and ice to slide or melt off without causing any damage to the roof or seeping through any cracks. The intent of roof venting varies depending on climate but it is the same if you re venting the entire attic or if you re venting only the roof deck. They let moisture and hot air exit the attic but they aren t nearly as effective as other types of roof vents and homes generally need to have several of these units for the best results.

Just make sure that rain and snow cannot get in. In cold climates the primary purpose of attic or roof ventilation is to maintain a cold roof temperature to control ice dams created by melting snow and to vent moisture that moves from the conditioned space to the attic ventilation acts to bypass the vapour barrier created by most roof membranes. Unlike box vents which are square off ridge vents are usually much longer and thinner. If you have loose fill stop it from blowing around by covering it with fiberglass batts or tyvek.

Roof system recommendations those designing low slope residential roofs in northern climates ashrae zones 4 and above should consider the following design recommendations. The common solutions to this ice problem are to use a higher powered fan use a larger diameter shorter duct run and wrap the pipe with better duct insulation. In a cold climate the primary purpose of ventilation is to maintain a cold roof temperature to avoid ice dams created by melting snow and to vent any moisture that moves from the conditioned living space to the attic. The intent of roof venting varies depending on climate but it is the same if you re venting the entire attic or if you re venting only the roof deck.

A michael maines answers and gives advice on the question about bath fan venting for cold climates.