van de Ven Construction LLC
Custom Builders and Insulation Specialists
Call us: 802-291-0403
Common Misconceptions - Ice Dams & Roofing
“Water leaks caused by ice dams are solved by a good roof”
Oh, if I could just line up with a good roofer, I would have more work than I could handle. It happens all too frequently that I get a call from an extremely frustrated homeowner with leaks. He was certain that the ice dams and leaks would disappear now he got a new roof. In reality, I often remove the perfectly good new roof, remove the joke of an insulation package -if any- and after properly insulating the area, install another new roof.... UPDATE: We now do our own roofing, even have our own standing seam panel forming machine.
“Ice Dams are a Way of Life”
Ice dams are commonly formed as follows: snow melts on the roof. The water runs down the roof and somewhere lower on the roof reaches a colder zone. Often this is where the roof starts to cantilever beyond the exterior wall below. As it freezes, it starts to form a dam. Meanwhile more water travels down the roof and meets the dam. As it meets the dam, it forms a pond. As the water in the pond rises, it works its way through the roofing. Even standing seam roofing is not resistant to this problem. Only pond liner is, but very few roofers ever suggest this.
Solutions:
1. Easy, heat up the cantilevered section of the roof. This is cheaply done but not shown in the code book, because it takes enormous amounts of electricity.
2. Hire someone to shovel the roof. Don’t do this yourself. I know of one homeowner that is quite undertaking and he has now a pin in his leg.
3. Not that easy, but somewhat effective. Install a section of smooth roofing at the area where it cantilevers such that ice dams hopefully slide off before turning into a problem. Gutters make this solution less effective.
4. Prevent the snow from melting prematurely. A very well insulated house has a pack of snow on the roof, except that at the edges, where it overhangs the exterior walls, the snow is already gone. Miracle, the insulation works... Oh, and the remaining snow, it is also insulation, further reducing your heating bills (snow has an R value of about R1 per inch of thickness)
“Hot roofs perform worse than cold roofs”
Nice blanket statement. The answer should be safe too: “yes and no”. Truth is that in the days of Fiberglass insulation, the ventilated roof (AKA cold roof) was a necessity. The moisture allowed to bypass the pitiful airsealing would condensate on the underside of the roof deck. Then, as the sun came out, the temperature in the proper vent would rise and the airflow that resulted would carry the moisture away, quickly drying the plywood. So, in that building scenario, a propervent - with a correct soffit inlet and ridge vent - would work well, albeit at a very modest insulation level. However, with new insulation products and meticulous attention to detail in regards to airsealing, I would argue that a hot roof performs better than a cold roof, as there is no space taken up by the proper vent and all available space in the roof frame can be used for insulation. Note I am thinking of a spray foam or dense pack cellulose insulated roof system here.
“Foam messes with my roofing warranty”
Most roofing product manufacturers warranty their product. If it is installed in compliance with their guidelines, and If so, then only the product excluding labor, and If so, then only a pro-rated amount. So, I think we all have better things to do than to chase some half-baked warranty. Also, if shingles survive the summer sun in Arizona with an airspace below it, why wouldn’t they survive in Vermont?
Also, the air space does not keep them cool, because for the “stack effect” to work in the proper vents under the roofing, there has to be a temperature difference between the air in the proper vent and the air outside. You know what that means right? The vent doesn’t work until the roof is hot. Poof - no cold roof.
