Friday, December 9, 2016

Heat lost through the windows!

Today in class we calculated how much heat was lost from windows due to conduction. This made me curious and I wanted to apply it to one of my dad's projects (he builds houses). This particular project is a "bunk house" for a family country home and has a lot of windows. These are the plans for the east side of the bunk house:

(SK Design Group; Pittsfield, MA)

The area for the "F" windows, after converting to meters is 3.2 meters squared, for "H" is 0.84 meters squared, "L" is 1.8 meters squared, and "R" is .94 meters squared. For simplicity, we are assuming the windows are solid glass with thickness .0191 meters.

Plugging these values into the equation for conduction (Q/t=kA ((T1-T2)/l), and adding all of the windows' totals together, I calculated that the east side of the bunk house loses about 16,700 Watts.  Since there are four sides to a house, assuming this is constant, we can say that the house loses roughly 66,800 Watts from windows and glass doors.

These windows aren't actually made of solid glass, however. They are double paned with a 13 mm "airspace" in between the glass panes to trap the heat inside. This prevents both conduction and convection. In the airspace, this particular project has argon gas in it, which is heavier than air and provides better insulation. It also helps soundproof, prevents frost, and can sometimes block UV rays. Some cons are that the gas eventually dissipates (at an unknown rate) and if there isn't a tight seal and the gas leaks out, you will never know. This gas isn't toxic and doesn't have an odor, but you could be losing your insulation without even knowing it.

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