Friday, March 1, 2013

Ice Damming

Can you see four inches of ice sitting on top of these gutters? 

Why does this happen on some houses and not others?

Can you see the snow is melted below the chimney and near the upper portion of the roof? 

Are there visible roof vents?  No.
Is there at soffit vent at the eave? No.
Is there a ridge vent? No.

We all know heat rises.  This rule of physics applies inside a house as well. 

The reason the snow melted on this house is that the shingles were heated from underneath even though the outside temps were well below 32 before this picture was taken.  The melting occurred from underneath. The water ran down the roof, and as it got out from above the heated area, froze and created a thick, heavy of layer of ice at the eave. 

This ice not only puts a lot of weight on a home's gutters, it can expand up under the shingles, and as it melts, find its way through the nail holes and create leaks in a ceiling or wall. 

The objective of a roof ventillaton system is to equalize temperatures underneath the roof with temperatures outside. 
As you can see from the illustration, there are several ways to vent your roof. 

Effective venting coupled with excellent insulation that keeps the heat inside the living space is the correct way to address a problem like ice damming. 

Another culprit that may create melting on your roof when temps are below freezing, even if you appear to have a well vented roof and proper insulation, is recessed lighting in the ceiling just below the attic.  The image below shows an infrared photo of a what a recessed light may look like in an attic.

These energy powerhouses can provide enough heat in an attic to raise the temperature under the shingles above 32 and melt the snow above them.

What can you do about this?  One idea is to change to a much cooler LED, or compact flourescent lit can.  Halogen bulbs have been the most common type of bulb in recessed lighting.  Try touching a halogen bulb after its been on for a few minutes.  They burn very hot.  Many can lights are equipped with high temperature shut off protection, so even if you can devise a way to prevent the heat from a halogen bulb from escaping into your attic, you have raised the risk of having your can lights shut themselves off because they get too hot.  LED bulbs burn at a fraction of the temperature of halogen bulbs and have become much more affordable than in the past.  They burn less energy and last many times longer than their halogen counterparts. 

Contact Integrated Home Inspections for more information on how you can alleviate ice damming at

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