Extreme Snow Conditions & Your Home

18 July 2023by Sandy Hill

What to Watch For

The heavy snowfalls that Ottawa has been receiving are just about over but some of the potential problems for homeowners are just about to begin.

Dry light snow and high wind conditions in Ottawa have presented some unusual problems not seen for many years.

One of these is a much higher incidence of snow entering through roof vents and accumulating in attic spaces where it eventually melts.

The ‘mushroom’ vent that has been commonly used for more than 40 years has been pushed beyond its design limits this year.

In response, some builders may switch to a new ‘chimney’ style roof vent that has begun to appear recently although roofers caution that even this design cannot be seen as a guarantee in preventing snow penetration under all conditions.

Unfortunately, there is no way for Ottawa builders, renovation companies or home owners to completely prevent this problem but if it does occur, the wet insulation should be removed as soon as possible and replaced.

Home owners who have experienced a significant problem this year should also give consideration to having their ‘mushroom’ vents replaced with ‘chimney’ vents in case this year’s extreme conditions are repeated at some future date.

The next problem resulting from this year’s heavy snow falls will likely be widespread reporting of ice-damming. This is a problem that can occur at any time but is most common in late winter where roofs are covered with a thick layer of snow and daytime temperatures begin to rise above zero.

The problem can be further exacerbated when the roof vents are covered in snow.

This prevents air from flowing through the attic and allows the temperature to rise to the point where the layer of snow in contact with the shingles begins to melt.

Water runs down the roof until it reaches the area just beyond the home’s exterior wall. At this point the roof temperature is much colder and the water freezes. As the process continues a thick layer of ice is formed that finally ‘dams’ the water from flowing down the roof and it begins to pool and back up under the shingles.

As the water is forced further up under the shingles it begins to penetrate the roof decking through nail holes and other small openings and drips down onto the ceiling insulation. In extreme cases there is enough water to penetrate the ceiling drywall and cause considerable damage.

Home owners should visually check their roof to make sure that all of the roof vents, including plumbing stacks are open and not covered with snow. If they are not open, the snow should be removed as soon as possible. Home owners who have experienced ice-damming in the past should consider having any snow removed from the lowest 3 feet of their roof.

While checking the roof vents it would also be worthwhile to quickly assess a few other important issues that could cause problems.

One of these could be basement window wells that are full of snow to the point where the window is no longer visible. Under these conditions, a fast melt, heavy or freezing rain may expose basement windows to extremes they are not designed for and they will begin to leak. In some cases it is worth removing the snow from window wells.

In older homes the furnaces were typically vented through the roof.

New natural gas and hi-efficiency furnaces, appliances and air handling equipment are now commonly vented out the side of the building not very far off the ground. In most winters this is not an issue but the depth of snow this year could completely block the vent and prevent the appliance from operating.

Similarly, fireplaces are no longer always vented above the roof. Gas fireplaces can have vents within 16 “of the ground if the unit is located in a basement and even a ground floor fireplace vent may vent close to the ground.

They say that “an ounce of prevention is worth a pound of cure” and given this year’s extreme weather conditions we believe it would be worthwhile to take 10 minutes to conduct the inspections described above because it could save thousands of dollars in damage and / or service calls.

Sandy Hill Construction

Phone: 613-832-1717

Address: Sandy Hill Construction Ltd.
35 G Robinson Ave.
Ottawa ON, K1N 8N8

Sandy Hill Construction