Best Practices Attic Ventilation

Ridge soffit vents importance of balanced roof ventilation.

Best practices attic ventilation.

Warm air that escapes living space also carries moisture that will condense on rafters or roof sheathing. For the best results place roof ventilation near the roof s peak and soffit vents in the eaves. For both attics and cathedral ceilings roof ventilation works best when it is balanced between high and low to take advantage of natural convection figure 2 55 at left. The international residential code irc provision for attic ventilation requires a ratio of one square foot of net free open ventilation area for every 150 to 300 square feet of attic square footage.

Do not use mechanical means electric attic fans. Venting a homes attic is a very important best building practices will say 50 at the ridge and 50 at the soffits unobstructed. 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. Best practices for attic venting pressurize the attic more ventilation at the soffits than at the ridge will allow the attic to be slightly pressurized irc 2012 requirements reflect this approach for best results provide 50 to 75 of ventilation space at the soffits 60 40 is the optimal split best practices for attic venting.

As a certified licensed home inspector it is not correct to say too much ventilation is bad for an attic unless rain moisture is getting in. If you see dampness or frost you need better roof ventilation and some attic vents.