Do you have a giant sheet of ice on your roof waiting to wreck havoc on your home? The last few Winters here in Toronto have been a mix of warm days and freezing days, the perfect storm for ice dam formation. Ice dams can not only damage the outside of your house, they do a lot of damage inside as well.
When snow falls on rocks and trees it comes in contact with something perhaps even a little colder and does not melt. It builds up until a combination of gravity and weight causes it to slip loose, and fall harmlessly to the ground. If on the other hand it falls on something warmer then it melts, and either dams (freezes again before it drips off) or runs off as water depending on the gradient.
How Do Ice Dams Form?
Here in Toronto, we go to great expense to warm their homes in Winter and that’s perfectly understandable. Unfortunately heat rises and despite best efforts at ceiling insulation some heat is inevitably transferred to the attic. This can be a result of inadequate insulation, or gaps caused by pipes and trapdoors. With the best will in the world, nature will always have a way, meaning that your attic will inevitably be a little warmer than the winter air outside.
This temperature difference causes the snow to gradually melt and travel down the roof. When it reaches the eaves that are at ambient temperature it freezes again, and gradually forms into a ridge. Above, the snow keeps on melting and adding to the pile of ice. As this grows in size the melt water becomes a dam pooling on the roof. Ice dams are a roofer’s worst nightmare come true.
This is because roof coverings work on the assumption that water will run off before it has time to seek out crevices and work it’s way under the shingles. This problem is surprisingly common on most roof surfaces except corrugated sheet metal. It’s worst of all on flat roofs and shingles.
Ice damming on roofs inevitably finds its way into the roof space below. There, it drips quietly onto insulation and accumulates on ceilings. If the leak is serious this can lead to minor flooding and damage to ceilings, carpets and upholstery. If the problem is minor then the attic becomes dank and starts smelling of mold.
The mold spores find their way past cracks through which the heat transfer happens. As they do so, they find themselves in an almost perfect habitat where they can procreate to their hearts content.
Tackling to Root Cause of Ice Dams
Ice dams exist because of differences between ambient and attic temperatures. Your wisest first point of call is to inspect your attic insulation because it’s pointless generating heat to melt the snow above and cause these problems. You may require expert advice because the problem’s probably lurking in an almost inaccessible place.
Your second line of defense is to improve ventilation through your roof so you constantly exchange the warmer air for cold. Point being, keep the attic as cold as the air outside. This can be effective in the case of steep roofs with gable ends. If you have a badly pitched roof covered with tiles or shingles you could be up for expensive alterations.
Have questions about ventilation and air quality inside your home? We’re happy to answer and questions, you can contact us here.