Roof Vents and Attic Insulation – How They Help

Roof vents and attic insulation can extend the life of your roof shingles by five, six or seven years, reduce your energy bills and save you money on repairs to rotting facia and roofing decks. Would you be curious to know how to do it?

Natural Resources Canada (NRC) discusses roof ventilation and attic insulation as a natural way to keep the summer heat from entering your home. Read more here.

There is a significant bonus to ensuring better ventilation and insulation in your attic, and that bonus is as big as your roof.


Roof vents and attic insulation go hand in hand to help extend your roof life in two ways; preventing ice damming and roof deck and shingle rot.

If all that is needed is roof vents and attic insulation, why are these processes so often done inadequately? Because it can be challenging to vent roofs with varied grades, valleys, dormers, hips, and skylights, and harder to create an air-tight attic space.


Crucial to a roof’s long life, proper venting and insulation can cost more money than some homeowners want to spend. This decision leaves your roof compromised.

Insulating an attic is an involved proposition. Pot light openings and holes for ducting, more often than not, are improperly insulated. Suppose air-tight seals are not made a priority. In that case, indoor heated air will escape into the attic in the winter and similarly, in the summer, your cooler air-conditioned air, although to a lesser extent, will be drawn out through the roof vents by the warm attic air.


How do roof vents and proper attic insulation prevent shingle degradation from ice damming?

Attic insulation and roof ventilation keep your roof cold during the winter. If attic heat transfers through your roof deck and your shingles to the snow accumulated on your roof, that snow will melt. The melted snow refreezes, forcing shingles apart (water expands when frozen), making them susceptible to lifting, curling and drying, which degrades the shingle.

Thawed and refrozen snow can become deep and heavy, leading to eave trough loosening, and facia rot from the constant moisture.


How do vents and insulation prevent roof deck and shingle rot?

Roof vents cannot stop attic condensation from occurring. Sometimes, there is more moisture that can be expelled through venting alone. That excess attic heat and moisture will transfer to the roof deck, eventually rotting it and, in turn, the shingles.

Not only does the roof deck’s wetness transfer to the shingles, but their glue strip degrades when they stay wet, allowing them to loosen and eventually blow off.

Granules on the shingle face add a layer of protection, preventing the shingle from drying out in the summer. Constant shingle moisture causes the bond between the granules and the shingle face to deteriorate.


Beauty often comes at a cost.

Architecturally interesting roof planes challenge future re-shingling, venting and insulation upkeep. Keeping your roof simple can mean less worry, but that does not stop most of us from wanting what looks most appealing. Forest City Roofing of London, ON, is here to help.


Good-to-know information about vents:

The Building Science Corporation has published an extensive article here to help explain proper venting and attic insulation.


Electric exhaust roof fans:

They can be so strong that they draw more air from inside your home (like your expensively cooled AC air)

Soffit vents:

Soffit vents are the preferred form of natural in-take venting. They draw cooler outdoor air into the attic to help modulate the temperature.

At the same time, soffit vents aid the cross-breeze within your attic; the cool air comes in from the soffit below, the warm air leaves out the top through the ridge venting, capped roof vents and gable end vents.

If insulation gets in that path, all the good intentions of venting stay in the attic.

Never let your painter paint shut the small holes of a soffit vent.

Revolving roof vents:

Revolving roof vents will not create a suction force that draws in air, which is good to know since capped roof vents, as shown in the diagram here, are a sufficient style of the vent to use.


See the diagram below, courtesy of Natural Resources Canada, that shows the basics for cross-ventilation of your attic from end to end and top to bottom.



Diagram of various Roof Vents


  1. Soffit venting (brings in cool air for your attic and is a key component of ‘cross ventilation)
  2. Gable end vent (sends out warm air)
  3. Ridge venting (sends out warm air and is a key component of ‘cross ventilation)
  4. Capped roof vent (sends out warm air)


Forest City Roofing has been assisting owners of roofs of all kinds for almost thirty years. We will help you determine whether your roof is suffering from a lack of improper venting or insulation. Call us at (519) 659 6937 or visit our blog to read more informative roofing articles.

We service your roofing, venting, or eave trough concerns in the London area.

May 20, 2021

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