Snowy Roofs Have a Story to Tell About Energy Efficiency

Posted on Tuesday Feb 05, 2013

Have you ever looked at rooftops after a snowfall and noticed that some hold the snow and others do not and that some homes have icicles hanging from rooflines and others do not?  Although a steeply pitched roof may cause snow to drop from a rooftop, when snow melts on rooftops it is because the house is not well insulated. If a house has poor insulation the snow will melt faster because more heat is escaping through the roof. On a cold day, heat from within your home will rise to the attic. If the attic does not block that heat from leaving, it will escape through the roof causing the snow to melt. If a house is well insulated the snow will remain because there is no escaping heat to melt it.

Sealing and insulating the "envelope" or "shell" of your home — its outer walls, ceiling, windows, doors, and floors — is often the most cost effective way to improve energy efficiency and comfort. The U.S. EPA and the U.S. Department of Energy estimate that a homeowner can save up to 20% on heating and cooling costs (or up to 10% on their total annual energy bill) by sealing and insulating.

You can use a snowy day to see if your house is properly insulated. A picture is worth a thousand words and these neighboring houses facing the same direction tell the story very well.

House 1.pngThis is House #1 after a light snow. Notice how the snow appears as small white stripes running up and down the roof showing where each roof rafter is located. This home has very poor attic insulation and likely no insulation between the rafters. Consequently, the heat from the house has risen through the attic and melted almost all of the snow off the roof. The wooden roof rafters provide a minimal amount of insulation and stop the flow of heat allowing a small amount of snow to cling to the roof. This same photograph shows the opposite situation on the porch roof above the front door and the roof overhangs.  They still have a full coating of snow because there is no heat flowing through those locations, just cold outside air. (Click on images for larger view)

House 2.pngHouse # 2 is a bit better and may be moderately insulated in the attic. You can still see where the rafters are located but there is more snow clinging to the roof. The insulation in this house is well distributed but there is not enough of it. We can conclude that there is still enough heat escaping from the house to melt much of the snow on this rooftop.

House 3.pngHouse #3 has a roof full of snow. There is no heat source to melt the snow and we know that this home is holding its heat. This is what a well-insulated home looks like and what your roof should resemble on a snowy day.

Here are two simple tips to seal and insulate your home: seal air leaks throughout the home to stop drafts; and add insulation to block heat loss in winter and heat gain in summer. Learn about more helpful tips from Energy Star on making your home more energy efficient here>>>. ENERGY STAR is a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy helping us all save money and protect the environment through energy efficient products and practices. 

Story by: Beth Baxter