Wednesday, February 27, 2013

Ice Dams

Have you ever seen a home that has newer looking or different color shingles along the edge of their house?  This typically indicates that the homeowner has experienced severe problems from ice dams.

Yesterday, most of us in Michigan experienced a wet, sloppy snow storm.  Many home owners are likely to experience ice dams as a result.

An ice dam is a build up of ice and water that works its way under shingles. When snow from the peak melts (caused by warm spots in the attic), water slowly runs down the roof.  When the water hits a cold spot on the roof (usually at the eaves), the water refreezes. As more melting water hits the cold spot, it begins to "stack up" and eventually works its way underneath shingles and sheathing.

The cause of the problem is either inadequate insulation, ventilation, or both. How to reduce the chances of ice dams:

1. If your attic space is unfinished (not used as a living space), the goal is to have the temperature inside the attic close to the outside temperature. To accomplish this you need:
    a. sufficient insulation between the floor joists of the attic;
    b. soffit or fascia vents;
    c. roof or ridge vents;
    d. all sources of heat loss, such as bathroom or kitchen vents, heating ducts, or heat pumps, well insulated to minimize loss of heat from them to the attic space.

Doing all the above allows cold outside air to come in at the bottom of your roof and escape through the top of the roof taking along any heat lost to the attic space.
If you have all the ingredients and are still experiencing a problem:
    a. inspect the insulation in the floor to insure it's not jammed against the end of the roof to close off circulation from the soffit vents; if it is, then pull the insulation away from the roof edge to allow air to circulate;
    b. inspect soffit vents to see that they are open and not painted shut. Sometimes vinyl soffit vents are installed over solid wood soffits making the vinyl vents useless. If so, remove vinyl soffits and drill 2-or-3" openings through the solid wood soffits every 12-to-18" respectively;
    c. check roof vents. Properly installed “ridge vents” are typically preferred over “can vents”.
    d. close any open gable vents. Air can short circuit by coming in gable vents rather than by coming in the soffit vents.

2. If your attic space is used as a living area and you have soffit and roof vents, fixing the ice dam problem can be expensive. You need to allow air to flow between the roof and the insulation. The ceiling and insulation must be removed, special ducting panels must be installed between each rafter, then the insulation and ceiling can be re-installed. 

3. Homes in Michigan should have an ice shield barrier installed along the roof edge. Existing shingles must be removed along the roof edge. The barrier is 36" in width.  Oftentimes more than one course of ice and water shield is needed. The shield is like a pool liner and doesn't allow water to seep through it.

Can owning a metal roof system help with the ice dam problem?  Yes it can.  In short, snow doesn't stay up on a metal roof as easily as it does on a granulated asphalt roof.  No snow on the roof to melt, no ice dam.  In fact, with metal roofing, we often have to strive for the opposite effect - keeping snow on the roof!  Since snow comes off of the roof so effectively, we often want to install "snow guards" along the eave edge of the roof especially along walkways and above doorways to minimize avalanching snow.  At Metal Roofs of Michigan, we specialize in addressing all the issues that a roof in Michigan faces and strive to provide you with a beautiful, long lasting roof that is free from those pesky ice dams.