Understanding Heat Transfer
Have you ever been outside in 50 degree air, yet comfortably warm when the sun is shining brightly on you? Or have you ever felt chilly, even when the air temperature was 70 degrees? If so, you have experienced heat transfer through radiation, and it is not related to air temperature. Radiation is the primary way our bodies experience temperature in our homes.
“Heat rises”. We’ve all been told that for years, and most of us have probably repeated it at one point or the other. But did you know that it is wrong? The second law of thermodynamics states that heat moves from hot to less hot. True enough, warmer air that rises, while cooler air sinks. We will take this up a little later. For now, consider what the second law means for our comfort in our homes.
In winter, the coldest thing in the house is typically the windows, with the walls being a close second. Even if you have an Energy Star rated window, it can perform as low as R-3.1! That is hardly impressive. That feeling of being cold is heat moving OUT of our bodies, and being radiated to a colder surface.