Proper Ventilation for a Healthy Roof


For proper functioning, your roof needs adequate ventilation. Like us, a roof needs to breathe in order to remain in good health. Roof ventilation isn’t typically done by a mechanical or electrical ventilation system, but rather by a chimney-like system – where air flows naturally due to temperature differences found in the attic.

Good ventilation prevents your roof from overheating in the summer and from deteriorating prematurely. It also avoids more serious problems from occurring, such as mold, rot and water infiltration. By reading the following paragraphs, you’ll discover the secrets of good roof ventilation and how to ensure yours is adequate.

How does roof ventilation work?

Roof ventilation consists in letting air flow through an intake (normally through the soffit) and exhaust (an evacuation valve) system. There are two methods to create an airflow in your roof: mechanical – which requires a power source – and natural.

The “natural” method is used most often. The soffit’s air intake combined with the wind outdoors, helps the air circulate naturally. As heat rises, the hot air that makes its way to the attic can exit through the exhaust valve on the roof, which then creates a suction (i.e. air intake) effect with the soffits. Regardless of the system used on your home or building, they allow air to flow through the roof – optimizing your insulation’s efficiency. It also helps reduce the average temperature of the roof itself. 

snow on shingles

The benefits of good roof ventilation

Why is it important to ensure our roof is well ventilated?

To extend the roofing material’s lifespan

When a significant amount of ice accumulates around your roof’s edges and gutters, it’s essentially an ice dam that’s forming. Ice dams occur when the heat within your attic – combined with that of the sun – melt the snow and ice on your roof. Then, the water trickles down the roof and freezes at the edges. It might seem harmless, but, beware. This ice build-up can easily make its way under your roofing materials and damage your roof, your attic, and even the inside of the walls of your home or building.

A well-ventilated roof is easy to spot during winter months; there is always snow on the roof, but not an ice cube in sight! Ventilation also helps the roof during the hot summer months. The roof’s temperature can double when the temperature outside rises. This heat build-up can damage your roofing from the inside out and deteriorate it at a rate of up to 2 times faster. A ventilated roof will allow hot air to escape and help prevent having to undergo a premature roof renovation.

toit de bardeaux en hiver

To prevent mold, water damage or structural damage

Even the best-built houses lose humidity in the attic. In winter, warm, humid air can create condensation (as seen in windows) inside a poorly ventilated roof. This condensation freezes on contact with the roof’s cold walls and can result in ice accumulation inside the attic. In the spring, as it gets warmer, this ice melts, resulting in water that can damage the insulation inside the roof, or even make its way inside the building’s walls. When the water doesn’t dry quickly, fungi and mold can easily develop. Over time, damage can become quite substantial and will require costly decontamination processes.

To reduce energy costs

Many of us use an air conditioner in summer. Seeing as heat rises, a well-ventilated roof allows heat to make its way out, reducing the workload of your air conditioner. An air conditioner that works less, means a lower energy bill! 

How to evaluate the adequacy of your roof’s ventilation

From the outside

Ice accumulation on the edge of your roof in winter and overheating conditions inside the house during summer months may be signs of inadequate roof ventilation. Unfortunately, if these problems aren’t resolved quickly, they’ll accelerate the roofing’s deterioration and they’re likely to promote water infiltration, especially during thawing periods.

icicles on a roof

From the inside

If you have water pockets on the walls or damp walls when spring comes around, these are possible signs that condensation has accumulated in your attic during the winter. Take note of your ceiling’s condition as well and keep an eye out for water or humidity.

From inside the attic

If you can easily access your attic, you should definitely go check it out after a few consecutively excessive cold winter nights. It’ll be well worth it. The humidity levels within your attic can come from inside your home as well as outside your home. Although a vapour barrier is installed between your ceiling and your attic, they’re never perfectly waterproof. This means that some of the humidity within your attic is likely to have come from inside your house through little openings. It’s essentially water vapour that makes its way to your attic through pot lights and other potential openings. When you get in your attic, keep an eye out for ice accumulation, especially under gables – if your roof is of a rather complex shape –  as that’s where air has a harder time flowing. 

 When you check the condition of your attic, pay special attention to bathroom and kitchen vents that pass through the ceiling, around plumbing columns, chimney flues, and at the entrances to recessed wires and lights. Pay attention to any sign of moisture/humidity:

  • Stains
  • Mold
  • Flaking rot
  • Dark circles on wood and insulation
  • Rusty nails
  • Strong and abnormal odours
  • Blackened wood

Inadequate roof ventilation could cause excess humidity (as it cannot evacuate efficiently) and condensation on various parts of the roof.

Spring is when snow melts and birds start chirping again. But, it’s also the time of year when a roof inspection may be required. So why not take the opportunity to make sure your home is well protected? After all, your roof may need a breath of fresh air too!

My roof is clearly poorly ventilated, what should I do?

Unless you’re a roofing expert yourself, we suggest you hire a professional roofer to take care of your roof’s ventilation. You might not need to redo your entire roof, that’s why getting a proper evaluation done is necessary.

Adding roof ventilators

Simple air vents (often compared to turtle shells) installed at the top of your roof is often enough to deal with minor ventilation problems in more confined areas of the roof. However, keep in mind that, due to their low profile, they can easily be blocked by snow during the winter, all depending on their location. You can also replace these small vents with more robust valves known as Maximums. Be sure to properly calculate your roof’s area to install enough Maximums. Typical roofs will have at least two Maximums installed. 

roof ventilator

Unclog or replace your soffits

When going to the attic, make sure the soffits around your house are not clogged. It’s common for the insulation material to move a little and eventually block the air intake, especially if the air flow is insufficient. Over time, your soffits may also have been taken over by birds, or dead leaves may have made their way in there. A good cleaning might be all you need.

If your soffits are not ventilated, it may be wise to replace them with another model, one with air holes that will allow air to circulate properly.


Re-insulate your ceiling

It’s possible that your ceiling’s insulation is insufficient and that the heat that rises from your home is the cause of the condensation problems or extreme heat in your attic. Re-insulating your ceiling will allow you to keep the heat inside your home and save on your energy bill, all while extending your roof’s lifespan.

Our Renovation Advisors will gladly assist you in finding the right roofing companies for the job you need to be done! Call us or fill out our form to start getting free quotes today.

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