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Importance of Roof ventilation System


Attic roof ventilation is an important element of a home’s design and construction. Without effective roof ventilation, excess heat and humidity can cause serious problems with costly consequences.Roof Ventilation is much more than steady, high volume of air movement. Proper ventilation requires an entire system of components, expertly designed to provide constant intake and exhaust of air.roofing-101-ventilationAny building, inhabited or uninhabited, must be provided with adequate roof ventilation so that it is not affected by the problems of condensation, mold and decay. Throughout the year, a non-ventilated building is more vulnerable to these types of problems.For example, in summer the heat generated creates a furnace and this directly affects the shingles as they are made of an oil-based material. On a +30-degree Celsius day, an attic can reach up to +60 degrees Celsius. This super-heating of the shingles dries their oils and causes the loss of the small stones, or granules, embedded in the asphalt to protect the roofing-101-iceshingles from UV-rays.In winter, the cool-room effect means both a colder home, which will require more heating and the formation of damaging condensation. This type of condensation can create mold, fungi and rotting roof timbers. Proper ventilation will allow the moisture to leave the attic and travel outside. If the attic is too warm during the winter, the precipitation frozen on your roof will melt, drip down to your gutters, and then re-freeze. This accumulation of ice can lead to water infiltration and damage your roof deck, creating health problem like mold.



Summer heat, trapped in the attic, creates a furnace effect, heating ceiling insulation, which then conducts heat through to the ceiling, and this heat is then radiated downward to persons and objects in the rooms below. This is why it is much warmer upstairs in the bedrooms than downstairs in the basement! Other problems that arise by this are the curling, or the bleeding of shingles, and the warping of the sheathing. An overheated attic, combined with moisture, can cause a number of problems, including damage to roof decking and roofing shingles, which can become distorted and deteriorate prematurely. Heat that’s absorbed in the attic can also radiate into the living space causing air conditioners, fans, refrigerators and other appliances to work harder. As a result, energy bills can increase.

Winter conditions bring a different type of problem. During the cold months of the year, the air inside the home is warmer and carries more water vapour than the colder, dryer air in the attic. Cooking, laundry, showers, humidifiers and other activities using water contribute to this condition. There is a strong natural force, termed “vapour pressure”, that causes water vapour to migrate from high-humidity air or materials to low-humidity air. First, the condensation can cause the deck to swell, resulting in waviness and buckling of both the deck and the shingles. Second, the water can rot the roof deck, destroying its ability to carry loads and its nail-holding capability. Third, severe condensation can drip onto the insulation, reducing its effectiveness and possibly seeping through to the ceiling below. Damp insulation causes wood rot, mold, and mildew, leading to poor indoor air quality in the rest of the home.

Another winter problem caused by poor ventilation is the formation of ice dams. Ice dams form in cooler climates during winter when heat collects in a poorly ventilated and/or inadequately insulated attic space. Built-up attic heat combines with the sun’s warmth to melt snow on the roof, even though outside temperatures may be below freezing. The flow of melting snow refreezes at the eaves and gutters. This freeze-thaw cycle can result in a pool of water that can back up under roof shingles and behind fascia boards, soak roof decking and wall sheathing, damage exterior and interior walls, peel paint and ruin ceilings. Current model building and energy codes include requirements aimed at reducing the chance of ice damming, which is more common in existing homes having less insulation that allows heat to escape through the attic and into the roof deck. For this reason, reroofing provides the perfect opportunity to reassess the roof and attic assembly and address any deficiencies while installing new roof coverings.


Recap of a what a good ventilation system will do:


  • Reduces heat build up during the summer and saves you money by reducing your air conditioning use.
  • Reducing energy costs in the winter.
  • Eliminates moisture that leads to black mold, mildew and wood rot.
  • Protects against the development of ice dams in winter
  • Extends the life of your shingles
  • Helps prevent premature roof failure
  • Protects the “R” value of your insulation