By Alex Madonik
Do you prefer warm or cool weather? Or are you more like Goldilocks, and like your weather 鈥榡ust right鈥�?
When it gets too hot or too cold outside, it鈥檚 time to find someplace more comfortable. Our houses are designed to keep heat in when it鈥檚 cold outside, and to keep heat out when it鈥檚 too hot. Heat is a form of energy, and it always transfers from a hotter place to a cooler place. This continuous transfer of heat is why it takes extra energy to keep a refrigerator cold, or to warm your house when it鈥檚 chilly outside. All that extra energy increases your environmental footprint.
We can save energy and stay more comfortable if we slow down heat transfer. The first step is to close windows and doors, because air carries heat with it. If it鈥檚 hot outside, and your window or wall feels warm, that means heat is still getting through. Any solid material can be a heat 鈥渃onductor.鈥� Metals are good at conducting heat, similar to how they conduct electricity.
To stop heat transfer, we need an insulator. The best insulator is a vacuum 鈥� in fact, that鈥檚 how a thermos works, by wrapping its contents inside a double wall, with the air in the middle removed. Having a vacuum is best, but air itself can also be a good insulator. We use insulating materials that trap air so it can鈥檛 move. Filling the hollow spaces in the walls of a building with a good听颈苍蝉耻濒补迟颈辞苍聽is a great way to keep the temperature inside 鈥榡ust right.鈥�
Heat is conducted through hollow walls much faster than when the wall space is filled with insulation. The more insulation, the better. This difference in the heat transfer rate is called the 鈥淩-factor.鈥� The higher the R-factor of a wall or window, the slower heat passes through it. A single pane of glass has an R-factor of 0.9. Feel the glass on a window when it鈥檚 cold outside, to know that an R-factor of 0.9 doesn鈥檛 do much to keep heat indoors. Heat will easily move out of a building into the cold outdoors. That doesn鈥檛 do much to keep houses comfortable. It鈥檚 better to have windows with聽two聽panes of glass, with a little space for air in between them, which improves the R-factor to 2. Triple-pane glass is even better! Most new buildings must have R30鈥揜60 insulation in ceilings, R15鈥揜21 in walls, and R13鈥揜30 in floors. The amount and type of insulation you have in your home depends on where you live and what the weather is like. 聽聽
Insulation can be improved by adding a layer of aluminum foil backing. This aluminum foil is bright and shiny, and can reflect heat radiation and keep it from passing through the insulation. This improves the R-factor.聽
Newer houses and apartment buildings are built with very good amounts of insulation. For older homes, that may not be true. One of the best things you can do for an older home is to add or upgrade the amount of insulation. Methods and materials for insulating homes are constantly improving. Perhaps one day you will discover a renewable insulation that is even more economical, safe, and efficient鈥� and make everyone鈥檚 footprint smaller!
Alex Madonik, Ph.D. is a Chemistry Instructor at Peralta Community College in Oakland, California.
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