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How Energy Flows Through Windows
Radiation:
| Energy moves through windows in both directions: into the house and out. Radiative energy transfer occurs in several ways. Sunlight (short wavelength radiation) is transmitted directly through most windows. And radiant heat (infrared) is absorbed by glass and then reradiated. |
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Convection:
| Air rises against the warmer glass surface and falls along the cooler surface in the space between the panes. These convection currents of air transfer the heat from one pane to the other. |
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Conduction:
| Heat conducts from the warmer to the cooler side of a window as each molecule excites its neighbor, passing the energy along. Conduction occurs through the glass, the window frames, and even the air as inert-gas fill between the layers. |
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Infiltration:
| The tighter the window and the better the weather stripping, the lower the air leakage that occurs through windows. |
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