Ventilation is all about temperature control and consistency.
Cold climate attic venting.
A whole house fan is a fan that exhausts air from the home into the attic and out the attic vents.
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 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.
If you vent through a soffit where attic vents are often located the moisture will get sucked back up into the attic or roof venting.
Attic fans benefits types why use cold climate venting what is an attic fan.
In hot climates ventilation is just as important for the opposite reason.
Use rigid metal ducting aluminum or galvanized steel with lengthwise seams facing up and joints sealed with foil tape or duct mastic or rigid plastic pipe.
Unventing roof assemblies in most cold climates decreases the heating load by about 10.