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Yesterday, on a walk around my neighborhood, I noticed that some of the houses had almost now snow on the roofs, while my house was covered in snow. So I took these photos of the north side of my and my neighbor’s house, and sent them to my kids on the blog to try to explain the difference. So what can you do with this? (WCYDWT)

1. January 13, 2011 7:51 pm

This question is a good one to ask. Good lead-in to an inquiry lesson.

If by neighbor you mean next door, then probably not a function of amount of exposure to the sun and angle of the sun’s rays on the roof.

Could be a function of the extent of the insulation in the attic of each house, your’s has less insulation so that the differential between the temperature in your attic closely approximates the outside temperature that would prevent melting. Whereas, more insulation in the attic of your neighbor might mean the temperature differential is greater. Warmer inside by even 4-5 degrees might account for more melting.

Any trees that are blocking the suns rays in your yard versus their yard. Hard to tell from the pictures.

Others?

Bob

• January 13, 2011 10:23 pm

Since my wife is an expert on green building, and we had our house air sealed and insulated over the holiday, I think I have the answer. Our attic is exposed to the elements, but it is fully air sealed and insulated from the first floor. Thus our roof stays pretty close to the ambient air temperature, assuming the snow/ice is nearly 100% reflective.

My neighbor likely isn’t married to an energy efficiency expert who insists on R-gazillion insulation and encapusulated crawlspaces, and so there is more leakage of hot air from the house to the attic, raising the temperature of the roof, melting the ice, and costing \$\$. Also, this process has a negative feedback, as ice melts, roof absorbs more sunlight, heating more, and melting more ice.

Our house is a 1920’s bungalow, and before we undertook this project, it “recycled” air with the outdoors every hour. I can’t begin to describe how much more comfortable the house is now.