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Here in Calgary, it is vital to vent your roof correctly. With cold, moist winters and hot, dry summers, the difference between the temperature outside our homes and inside can be drastic. The bigger the difference, the more our homes need to inhale and exhale properly.
When we're bundled up inside against the cold Canadian winter, we are breathing out moist air, with such daily activities as cooking with water and taking hot showers. All that moisture needs to go somewhere. As it makes its way up to the attic, it requires a little help in getting up and out. Otherwise, the moisture can cause mould and mildew, dampening insulation.
Besides removing moisture, a well-designed ventilation system will keep warm air from building up in the wrong places.
For instance, when a snowy roof has an attic of warm, static air under it, ice dams can build up. Warm air gets stuck near the eaves and melts the snow above. Nighttime temperatures drop and the melted snow becomes ice. This chunk of ice can damage roofing, tear gutters and even fall on people below. Leaks spring up when backed up water can't flow off the roof. Getting that warm air moving up and out is the key.
Considering our unique weather in Calgary, here are the top 5 applications which fit our climate best.
Because of their design, you will barely know these exist just by looking for them on rooftops. A roof-long narrow gap is cut in the sheathing of the roof. Roofers then install a cap that leaves a space under it which is sufficient to allow air to vent out. They are installed at the highest point in the roof, as this is the optimal place to allow hot air out. And, due to its length, it allows a tremendous amount of air out.
These require expert installation, creating a long horizontal cut in the peak of the roof's sheathing. And, they function well with soffit vents, but do require more skill to install.
Great care must be taken to install the correct type so that it won't be affected by snow on the roof. There are types of ridge caps that can be rendered useless if covered in snow. Whalley Roofing carries the correct ridge cap vent systems that account for snow buildup.
By far the most common vent is the static, or box, vent. Easily recognizable by their rectangular (usually), and low-profile shape, they are usually made of plastic. They work in a way that is similar to ridge cap vents by letting the hot air to rise, as it always will, and providing an escape route. But instead of one long penetration at the ridge line, many smaller holes are cut where they will be most convenient.
Due to their passive nature, it can be difficult to get adequate air exchange in a severe climate like that found in Calgary. It takes numerous vents to get adequate airflow. This is not an area where it's a good idea to skimp. Furthermore, be sure your vents come with secure screens to keep bugs and debris out.
You may see these near the peak of residential roofs. They have a bulbous, almost mushroom-like shape and spin like crazy at the slightest breeze.
Even on a calm day, there is usually a bit of wind at the roof level. Turbine vents, or “whirlybirds” take the smallest of breezes and get a nice spin going. This spinning action creates a suction effect that draws warm air up and out of the attic space. Because this air is typically hotter than the outside temperature, it is already looking for an escape route.
By adding a bit of “oomph” to this process, the turbine vent boosts the process of sucking in outside air through gable vents and forcing it out into the atmosphere.
Turbines can develop a squeak over the years. This is easily solved with a bit of lubricant every few years. Installation should be left to the professionals. Shingles have to be altered and worked around. Leaks can develop without proper fit and sealant. Finally, they require wind. Without wind, there can be no ventilation. Another consideration is durability when you live in a region prone to hail damage, as their performance can be impacted by damage like the image above.
This type of vent looks like an upside-down pie pan, aluminum mixing bowl, or UFO. It covers a motor which sucks air out. It's usually silver. Furthermore, it will dependably move air out of the attic. These are wired in to your home's electrical system, using a small motorized fan to pull the air up and out.
Because they are wired in to the house's electrical system, they require more skilled expertise to install and cost more money, both for supplies and labour. The wires and motors can fail unexpectedly, rendering them useless until a technician can repair them. Moreover, if the power goes out, so goes your ventilation. Finally, studies have shown that power vents can actually suck cool air out of an air-conditioned home and help move hot air in. As such, these actually do need to be calibrated and monitored.
If you see a pizza box sized solar panel on a roof, you might be looking at a solar attic fan. Solar-powered attic fans function the same as power vents, except they use a small solar panel to power the fan that pulls moist, hot air out of the attic space.
As with all solar applications, you require the sun to shine to make these work. With over 300 days of sun per year, this is of little concern to folks in Calgary. However, they can get dirty and require occasional cleaning. Finally, they can be difficult to control, and might pull out too much air or not enough.
With so many options, it's well worth it to get a local experienced roofing contractor to walk you through all the alternatives. Always ask your roofing contractor which type of attic ventilation they intend to use and why. Get them to explain it to you. A professional roofing contractor will have an explanation, as that factors in your home's orientation, roof design, snow load and pitch can influence what course of action to take. Whalley roofing has been making those expert decisions for 25+ years in Calgary. And, because we do roof snow removal, we can combine services to keep your home buttoned up and protected, regardless of what any Arctic blasts bring your way. We know the weather, and we know what works here.