Having recently gone through a stint of VERY cold weather, including some snow, ice, and sleet, I noticed several homes and businesses that need additional insulation. How can I tell from the outside? Take a look at these two different roofs.
Notice the stripes? That is where the rafters are keeping attic warmth from escaping through the roof. Where there is no rafter, the snow melts more easily, revealing the tell-tale stripes.
Take a look at this second roof. This picture was taken about 10 minutes later.
No stripes showing on this home. It probably has the proper amount of insulation in the attic area. How much is enough? The US Department of Energy can give you specific insulation recommendations based on your zip code, heating source, and whether your home is new or existing.
While we’re at it, did you notice in the first picture, that the snow was thicker at the bottom and sides of the eaves? That’s because there is no warmth in an overhang.
This is a cross section of a typical house. Notice how the insulation only goes out to the exterior walls. When snow falls on a home (such as the first one) and begins to melt from the heat lost through an inadequately insulated attic, the moisture drains down the shingles and into the gutters. Sometimes, though, an ice dam can form on the overhang portion of the roof and cause substantial problems. Here is a picture of what happens with a roof ice dam:
In this unfortunate situation, rain water or melting snow hits the much colder section of the overhand and because the gutter is ALSO full, an ice dam forms. Subsequent water draining down the roof hits the ice dam and begins backing up under the shingles where it can eventually rot the framing materials and/or cause a leaky roof. Then it’s compounded by wet insulation lying next to your home’s framing members.
What can you do to prevent ice dams?
First, make sure you have the correct amount of insulation. Second, keep your gutters clean. Third, if possible, install a bituminous membrane on your roofing deck that will keep any water from penetrating your roof framing. These membranes are usually three feet wide and have a seriously sticky backing. They seal around any nails that go through them and are called Ice and Water Shield or Ice Dam Preventer. In colder climates, it’s a regular practice to install this membrane on new construction, but if you live in an older home, it may not be there.
Photo credits – ME!