proper ventilation on roof

Properly spaced and installed vents by Archer Roofing will prevent heat trapping in attic.

warped and lifted shingles

Lack of ventilation has lead to shingles warping and lifting due to heat intensity

Published by Pawel Matonog

It might seem ironic, but the fact that modern homes are much better built these days, using advanced insulation materials and methods, has lead to more condensation formation and heat trapping if there is inadequate ventilation on the roof. Because most homes are now air ‘tight’, they allow minimal infiltration of outside air. These super insulated homes have greater energy efficiency, but because the colder, drier air is kept out, the indoor air holds greater amounts of moisture, leading to a variety of structural problems. If proper attic ventilation systems have not been correctly sized and positioned on a roof to provide constant air flow, a modern home will have heat build-up and condensation in the attic.

Poor ventilation causes heat build-up in the hot summer months of up to 60°C on a 30°C summer day. If the unventilated attic has heavy insulation, this heat will stay there most of the night, slowly making its way to the home’s interior. An

Rotting roof decking due to condensation

Archer Roofing removing rotting roof decking due to condensation

overheated attic combined with moisture will eventually lead to a rotting roof decking, wet insulation, blistering, distortion and the curling of roofing shingles.  In the winter, warm, moist air will rise through the ceiling area into the attic, especially though electrical and plumbing fixtures. In the cool attic, this moist air will condense on the cold rafters, and roofingsurfaces, dripping onto the insulation, reducing its effectiveness and possibly seeping through the ceiling below. As well, condensation can soak through the attic side of the deck, causing swelling of the deck, waviness and buckling of both the deck and shingles.  Ultimately, the water can rot the roof deck, destroying its load capacity and its nail holding capability, as seen on many Toronto roofs by Archer Roofing staff.

inadequate ventilation and condensation buildup on skylight

Condensation buildup on skylight and snow melting in freezing temperatures due to inadequate ventilation

Lastly, this built up attic heat in the winter leads to the creation of ice dams, which is the melting of snow on a roof, even in freezing temperatures. Then the flow of melting snow refreezes at the eaves and gutters. This freeze/thaw cycle results in a pool of water that can back up under roof shingles and behind fascia boards, soaking roof decking, wall sheathing, damaging exterior and interior walls, which leads to peeling paint and ruined ceilings. Soaked lumber and building materials lead to wood rot, mold and structural damage of a home.

skylight rotting deck board

Rotting deck board beside skylight due to lack of ice and water shield installation

Effective attic ventilation provides year-round benefits by creating cooler attics in the summer and drier attics in the winter. This ventilation is a crucial factor in protecting against damage to roof materials and structure, helping to reduce energy consumption and preventing ice dams. Not only is the life of your roofing shingles greatly extended, but also your home is protected against the serious nature of structural decay from condensation.

new wood roof deck

Replaced rotting deck board can once again bear loads and nails

It is also important to note that ventilation alone isn’t a complete solution either. It must be used with a waterproofing shingle underlayment and adequate insulation in the home. Archer Roofing installs a quality underlayment by CertainTeed in key areas of the roof to prevent water from penetrating to the roof sheath. Our company understands and follows the National Building Code for adequate ventilation, which is also required to validate the shingles manufacturer warranty. In all cases of roof replacement, Toronto’s best roofing contractor, Archer Roofing, follows the most stringent applicable building codes. Call us for a free inspection of your roof at 416-427-2437.

proper ventilation on roof

Properly spaced and installed vents by Archer Roofing in Toronto