Hot Weather Window Tips

Adapted from Real Goods Solar Living Source Book,edited by Doug Pratt and executive editor John Schaeffer.

The main source of heat gain through windows in the warmer months is from sunlight. Here are some tips for handling the sun that will help keep your house cool.

• Install white window shades or mini-blinds. It’s a simple, old-fashioned practice. Mini-blinds can reduce solar heat gain by 40-50 percent.
  
• Close south and west-facing curtains. Do this during the day for any window that lets direct sunlight in. Keep these windows closed, too.
  
• Install awnings
  Another good, old-fashioned solution is to install awnings. Awnings work best on south-facing windows where there’s insufficient roof overhang to provide shade. Canvas awnings are more expensive than shades, but they stop the heat on the outside of your building, and they don’t obstruct the view.
  
• Hang tightly-woven screens or bamboo shades outside the window during the summer. They’ll reduce your view, but are inexpensive and stop 60 percent to 80 percent of the sun’s heat from getting to the window.
  
• Plant trees or build a trellis
  Deciduous (leaf-bearing) trees planted to the south or particularly to the
  west of your building provide valuable shade. One mature shade tree can
  provide as much cooling as five air conditioners (although they’re a bit
  difficult to transplant at that stage, so the sooner you plant the better).
  
• Deciduous trees block summer sun, but drop their leaves to allow half or
  more
  of the winter sun’s energy to warm you on clear winter days.
  
• Apply low-e films
  Low-e films are thin metal coatings allow the shortwave
  radiation of solar energy to pass in, but block most of the long-wave
  thermal energy trying to get back out. Low-e films block most solar heat
  gain while transmitting most visible light.
  (see shop for supplies, below)
  
• Exotic Infills
  The other new technology commonly found in new windows is exotic infills.
  Instead of filling the space between panes with air, many windows are now
  available with argon, or krypton, exotic gas infills that have lower
  conductivity than air, and boost R-values. These inert gases occur naturally
  in the atmosphere, and are harmless even if the window breaks.