The lifespan and efficiency of a roof can be directly impacted by how it is – or isn’t – ventilated. Whether for cold or more temperate climates, designing and incorporating proper ventilation into any structure is key to ensuring a roof’s maximum possible lifespan and highest cooling efficiencies.
Ventilation has become such a vital industry issue that, in 2008, the Asphalt Roofing Manufacturers Association (ARMA) and six key industry roofing ventilation companies joined together to form the Roof Assembly Ventilation Coalition. Its goal: to advance developments in roofing ventilation and to educate contractors, specifiers, builders, architects, engineers, building code officials, municipalities, and the public about the benefits and importance of proper steep-slope roof ventilation.
While perhaps seeming counter-intuitive at first thought, repeated examples prove that in cold, snowy climates, ineffective ventilation can significantly increase moisture related problems inside the living space and attic. In a ventilation-poor structure, water vapor generated through the most routine of activities such as bathing, cooking, cleaning and hand-drying clothes indoors can eventually reach the cold underside of a roof deck and condense. Left unaddressed, this moisture can cause serious damage to the attic space and even the living space below, such as rotting of the wood deck and wetting of insulation, plaster and drywall,
Ice dams — and the serious damage they can cause — can also stem from inadequate ventilation. Typically, these dams are found at the roof eaves and are formed by the continual thawing and freezing of melting snow or backing up of frozen slush in gutters. Warm air rises to the deck’s underside causing snow to melt down the slope of the roof. Upon reaching the eaves or overhangs, the melted snow can refreeze and force water under the roof, damaging a home’s ceilings, walls and insulation. These dams can also easily harm the roof’s edge, tear off gutters, and perpetuate damage from the ongoing freeze-thaw cycle.
Proper ventilation helps prevent ice damming by encouraging a consistent temperature from the eave to the ridgeline. Proper levels of attic insulation based on geographic climate zone and water proofing shingle underlayment can help eliminate or minimize the damage caused by the formation of ice dams as well.