What’s the first thing that jumps out at you when you look at the house below?
Since I was called to inspect it, first thought was damn, that’s a lot of glass. Second, with a size of 7,000 sq. / ft., that’s a lot to heat up.
Windows and doors are the greatest source of wasted energy in your home. They experience the most heat transfer. That’s because heat always diffuses from warm to cold areas. In the winter, warm air from inside your home is trying to escape through your windows. Increased energy efficiency is usually one of the main reasons homeowners replace their old windows and non-insulated doors.
Most popular windows are casement and double hung. Do you know which one has the best seal?
A double hung window has two movable sashes which move independently within a window frame. With casement windows, there’s no track to slide up and down on, which means that casement windows can have a tighter seal when cranked shut and locked than double hung windows can. A tighter seal means a slightly higher energy efficiency rating. Here is an example of how I implement thermal imaging for comparison of heat transfer during my inspections.
The blue shadow on the perimeter of the casement window is cold air leaking in, which implies energy (heat) loss.
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In comparison, the double hung Fig 2 illustrates energy loss between the two window sashes as well as along the perimeter. The outside temperature at the time this photo was taken was 5°F.
As you can see the casement window performs slightly better than the double hung windows in terms of energy savings because of their tighter seal. Nevertheless, both windows still contribute to energy loss. Possible solutions are window treatments (i.e., honeycomb blinds).
Check out my finding on the honeycomb blinds installed in my house. That day these photos were taken the outside temperature was 3 degrees. In figure 3b we can see the cold trying to make its way in..
Surface temperature on the blinds is 64.8° room temperature is 68° fig 3. Glass surface temperature in figure 4 is 35.2 ° a 29.6° difference from the surface temperature of the blinds.
Exterior surface temperature seen in figure 5 is -5.6° I think we can agree that’s cold.
In figure 6 we have dual double hung windows behind one large honeycomb blind.
Frost buildup seen in figure 7 is trapped between window and honeycomb blinds as seen in figure 8.
Conclusion: To be effective, window treatments must trap air between the shade or blind and the window glass. The blinds create two layers of insulation, interrupting the convection reducing energy loss. First layer is dead air trapped between the window and the interior blind surface. The second layer is air locked into the honeycomb blind itself. Last the blind is reflecting the heat back into the room. End result less heat loss, reducing my energy consumption.
Full disclosure, I must admit I know nothing of window treatments; my wife purchased these honeycomb blinds. Never heard of them or knew they existed prior to her purchasing them. My only goal is to reducing my energy costs. I can only tell you firsthand they have improved the heating and cooling efficiency in my home. While researching this article I came across double air pocket honeycomb blinds offering even more insulation. If you have low quality windows and can’t afford replacements this may be a solution to help reduce energy costs. Keep in mind even if you do replace the windows in the future these blinds will still help in reducing energy costs. Do the research and see if this may work for you.
One final tip, go through your home and make sure all windows are properly locked and closed for the winter. As a home inspector I find very few homes that the windows are completely sealed.
