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Mother Nature's Free Heat Loss Analysis

We don’t get a lot of snow here in Atlanta, but when we do, Mother Nature provides us with a beautiful example of what winter looks like for our neighbors in the northern states.  But she also provides us with a perfect opportunity to investigate the signs of heat loss by simply looking at the roof.  To the average Joe that doesn’t sound like the greatest activity to perform when there’s snow on the ground. When you’re a building science geek, it’s almost as good as grabbing a sled (maybe).  After getting 4” of snow the other day, I took it upon myself to walk around my neighborhood and take photos of my neighbor’s roofs.  Besides realizing why the roofing companies stalk neighborhoods like mine like the paparazzi stalk celebs (there all quite complex, confusing at times, and subject to colossal failure), the patterns left in the snow on the roofs give me a great indicator as to the heat loss experienced by many of the homes.

For instance, in this first house, notice that there are several areas where the snow is uniform in appearance and then there are areas where there is no snow at all.  Did the snow just not fall on this part of the roof?  One of my neighbors pointed out that “Well that’s just the areas that the melted snow runs off”.  The only problem with that statement is that the temperature never made it above freezing and the skies were thick with clouds, so the sun didn’t cause the melting.  So where did the heat come from?  Remember the second law of thermodynamics stated simply says hot goes to cold.  So in this case the only possible source for heat is from the inside of the home.

After looking at several homes, you start to notice a pattern.  In this next photo, note that the melted areas are located along the side of the dormer and next to the foyer entry area.  Both of these spots are notorious knee wall areas.  Remember that knee walls are the vertical areas between conditioned (living) space and attic space.  They are often poorly insulated and never air sealed.  Combine the fact that hot air naturally rises and is trying to escape to the cold with an area that is consistently a weak point in the homes thermal and air barrier and you get what you see here.  In the northern parts of the country it causes a condition called ice damming.  While the icicles look pretty, they are not only dangerous but they cause water to back up under the roofline and all of a sudden you have water damage in the walls and ceilings of your home.

In this next photo, note that a large area to the left and above the room over the garage is completely free of snow.  No wonder this homeowner constantly complains about comfort issues in the bonus room.  To melt that much snow in that specific an area, you have to have a large amount of heat loss.  Keep in mind, areas that create large amounts of heat LOSS in the winter, also create large amounts of heat GAIN in the summer.  Addressing these areas not only increases the comfort in the home, but also reduces the cost of heating the home.  A house that’s more comfortable and costs less to live in, hmmmm, what a novel idea.


By way of comparison, let’s look at the next house.  Note that the snow coverage on the roof is fairly uniform all over.  I happen to know that this homeowner actually had air sealing performed in his attic prior to increasing the amount of insulation.  Because both the thermal and air barriers were addressed, there is very little heat loss.  Funny thing is you can tell there is a small area to the left of the bonus room window that is melting.  Again, a sign of heat loss from an area that was missed by the insulation contractor.

So if you want to have that pretty roof covered in a uniform blanket of snow (when it snows of course) you need to address both the thermal and air barriers in your home.  How do you do that?  Why by having an energy audit performed on your home of course.  Often these areas are not as obvious as you would think, and a certified energy auditing professional will know where to look and will be able to give you the proper direction you need to fix these problems.  Sure a proper audit is not free, but it will end up saving you a ton of money in the end.


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