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Blocked Proper Vents Causing Ice Dams
With winter quickly approaching I thought it was time to discuss one of the problems that causes ice dams. Ice dams cause significant amounts of damage each year and most of them can be avoided if you understand the root cause. The following information should help you understand some of the causes of ice dams.
Proper Vents
Proper vents are used to ensure proper ventilation from house ventilated eaves up to the ridge vent. Proper vents are typically made of styrofoam and come in many different shapes and sizes. The one shown in the picture is fairly representative of the ones sold today. The proper vent creates adequate air flow from the eaves up past the insulation material.
Blocked Proper Vents
Yesterday I went and looked at a house that’s having trouble with ice dams. The house is only a year old and the owner is quite frustrated at the poor performance. He asked that I come take a look at the house and see if I could identify any deficiencies that might be causing the ice dams.
Sure enough when I visited the house I was surprised to see a rather significant ice dam along the eave on the north side of the house. So I ended up going into the attic to inspect the insulation and ventilation. It only took me a minute to diagnose the problem that’s causing the ice dams.
The proper vent that was used during construction appears to be a very flimsy / cheap version that actually collapsed when the insulation was installed. Apparently the insulation crew stuffed the insulation so tight against the proper vent that the air flow was cut off. Basically this caused a very limited amount of air flow and thus the ice dams.
This is a perfect example of cheap materials and poor construction techniques creating a very serious problem. The house is just barely a year old and they have ice dams causing water damage. So if you’re having trouble with ice dams on a well insulated house it’s likely to be a lack of proper ventilation that’s causing the problem.
I had a similar problem. I hired someone to add blown fiberglass insulation into my attic and they sprayed it all over, including into my proper vents! Big problem. Luckily I caught it in time and had it fixed before it became catastrophic.
Good post! Our house was so prone to ice damming that after only 10 years the roof was completely shot and the previous owner has leaks in every room. But it wasn’t because of the venting it was the lack of attic insulation. There was only 4-6″ of blown in insulation in the attic! We fixed that right away and added two layers of R-19 batt.
Very good information in this article.
About two weeks ago I was in an attic of a home that was re insulated last year buy another contractor with blown cellulose insulation.
They did not install any proper vents thus blocking the air flow from the soffit.
Inadequate ventilation can lead to ice dams as well as premature shingle failure. Something so inexpensive and easy can create thousands of dollars of damage if not done properly.