Window Basics and Tips for Improving Light and Heat

So, what are some window basics and tips worth remembering? For starters, how windows interact with hot and cold temperatures and humidity can definitely help in making the right design and purchasing decisions. There are four types of heat loss through ALL windows:

  • Air leaks directly in and out from gaps along the edges (infiltration).
  • Heat passes through the window glass (conduction).
  • Heat energy flows from a warm object toward any cooler object nearby until equilibrium is achieved (radiation). This can cause up to 65 percent of the heat loss from your home.
  • Because heat rises and cool air sinks due to different relative densities, the cold air at the interior surface of an icy windowpane flows toward the floor, sucking more air behind it toward the window (convection). This movement eventually causes the overall room temperature to drop. This is why it's so important to cut off the flow of air in the vicinity of the window, e.g., create air gaps. [source: Brighthub] This is the same principal as an entry way air-lock).

Window Basics and Tips for Improving Light and Heat
If you have a passive solar home(or you are considering incorporating) passive solar strategies in your "greenovation", review these general tips and guidelines to improve passive light and heat in your home:

  • Southern or south-eastern exposure with properly-sized windows extend your natural daylight and admit solar heat which can be stored in solar thermal collectors or thermal mass (such as gravel, concrete slab, water column, or phase change walls) during the day and released at night.
  • Southern windows should be kept clean to admit the most amount of light.
  • In higher latitudes, properly sized overhangs extending from the roof over the home can reduce the seasonal heating and cooling admitted through windows (caused by the sun's changing angle). Among the many advantages of overhangs are the ability to admit the sun's light during the winter months when the sun's path is lower in the sky and prevent overheating in the summer, when the sun's angle is higher in the sky.
  • To avoid air leakage, install tight-fitting, preferably insulated window shades or curtains on drafty windows. (make sure your windows are weatherized first).
  • Close your curtains at night to prevent heat loss and open them during the day. Make sure your window treatments create a seal that "separates" the window from the interior of the house.

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