Here in Minnesota we can get a lot of snow. It doesn’t happen every year, but when it does, it causes ice dams on many homes. There are a considerable number of causes and numerous solutions. We’ll start out by explaining how ice dams form and the principles behind it. We will then go into what we will do to stop them.

The ideal conditions for ice dams are lots of snow and not too cold of temperatures. It has to be below freezing to form ice dams, but the colder it gets the slower the ice dams form. What happens is that the outside edge of the roof is cold, either due to an over hang or just the fact that it is more exposed to the outside air temperature. The snow further up the roof is melted due to some source of heat. Not a big surprise since right below this portion of the roof we like to keep our homes at a livable temperature. This melted snow flows down the path of least resistance and when it hits the edge of the roof it freezes. Over the period of a couple of hours, days or weeks this melting snow starts to build to eventually form the ice dams. Dam is an ideal word for it since it ends up big enough to stop the water completely. Shingles are engineered to defend against water flowing down the roof, but, the ice dam, which just formed, is puddling the water behind it and pushing it back up the roof. That is where the Problems begin.

Since the ice dams form from liquefying snow on the roof when the temperatures are below freezing we need to discuss how the heat is transferred to the roof. We will start with a discussion on the 3 methods of heat transfer: convection, conductance, and radiation.

Convection is generally considered the most effective type of heat transfer. This is when air is allowed to flow freely from within the house to the attic. In your house, it can occur if there are air leaks into the attic or any cavity that’s exposed to the roof deck. The solution to this is to seal up any cracks, hatches, electrical outlets or other methods of air movement. The attic is separate from the heated area, so most air movement is stopped, but even a bit of flow can mean large heat loss to the attic and roof.

Conductance is the next most effective kind of heat transfer. This occurs when heat is allowed to flow through materials such as plaster, sheetrock, metal, wood, and insulation. All materials allow some amount of heat to flow through. Metals allow the most heat to be transferred and insulation is meant to allow the least amount of heat transfer. Your best shot to combat conductive heat transfer is to add more, or better, insulation. Occasionally other stuff in the attic conduct heat. These things might include heating ducts or plumbing stacks. They may require some added insulation around them as well.

Radiant heat flow is the least effective. When you’re talking about heat from your home it’s not as significant of a factor compared with the other two forms. Nevertheless where radiant heat is an issue is when the snow is not distributed evenly over the house. If some of the roofing is exposed on a sunny day, its darker color will absorb more heat from the sun and melt the snow that way. This is usually caused by the elements and there is little that may be done to protect against it.

So when it comes to stopping ice dams from being a problem, the solutions are what are referred to as the big three: venting, insulating and waterproofing.

Venting keeps the attic near to the outside air temperature. What this does is keep the snow from melting at times when the temperature is one or two degrees below freezing. If the snow isn’t permitted to melt and flow down to the edge to freeze again, we have prevented the ice dam from forming. This is effective because it uses convection, the most effective form of heat flow, to keep the attic close to the outside air temperature.

Insulating keeps the heat from passing thru the building materials. Currently, spray foam insulation is considered the best insulation. There are 2 main reasons for that. First, for its thickness it out performs other materials. 2nd, when installed, it forms an airtight seal, stopping almost all air from getting into the attic. There are still many benefits to going with other kinds of insulation such as fiberglass. Actually, many people spray a couple inches of foam and cover it with an acceptable quantity of fiberglass insulation. These foam options can be pricey, nonetheless , just adding some insulation to your home may help forestall ice dams.

If your roof was redone it the last 20 years, or so , you have some kind of ice specific waterproofing. This is often in the shape of a membrane which is laid down along the outside edge of your home and up the valleys. This membrane is designed to glue itself to the decking and around each nail that is put through it. It does a good job at stopping water, regardless of whether ice dams form. Nevertheless many folks with ice dams can tell you it’s less than perfect.

Ice dams form during specific winter conditions and are not completely avertable. To mitigate the potential negative outcomes, contact a professional roofer to discuss your options. We are here to help.

Les Jones Roofing

Les Jones Roofing provides the highest quality roofing services in the Minneapolis, St Paul and greater Twin City Area as well as Across the state of Minnesota and Wisconsin.Roofing MN is a passion for us.

categories: Roofing,Minnesota,Roofers,Ice Dams,Cold Weather,Home Imporvement,Home service,Home repair