Solar Shades: Cheap Passive Heaters

One can reduce one's heating bills and CO2 sinning by installing inexpensive solar shades. The porch windows were equipped with five pull-down shades that generated quite an amount of heat.

Being a nerd, time and temperatures were kept for a period to document benefits. Not only was the air temperature measured but small thermometers attached to the back of the shades indicated the temperature that the reached, normally 110 degrees or more. The total surface area of the shades was about 140 square feet (5x7x4). Needless to say, understanding the thermodynamics of this temperature and surface, a hot porch should not be surprising.

The following are some roughly listed results. Normally, on a sunny day, by 10am the porch/house door was opened to share the passively generated heat with the house. The porch temperature has reached 80 degrees (which this person finds uncomfortable, especially when wearing de rigor winter long-johns!)

Normally, most of this sunlight energy goes into breaking down molecules that make up the colors and furnishing of our rooms. Interestingly, the optimal heat transformation of radio energy is the bedrock of quantum physics: black body radiation (e=hf).

  1. 0712?? Outside 38 degrees, shades at 110, temp at 65 degrees
  2. 071231 Temp outside 45, porch 70 degrees ... front door of house open with thermostat set at 49 degrees ... house temp ... Cannot stand next to shade, feels like lying on a beach on a hot, cloudless day.
  3. When the sun shifts past the shades, the temperature drops to the outside temperature.
  4. 080101 Propping open the front room door causes the porch temperature to drop ten degrees from 70 to 60 as inside cooler air (themometer set at 49 degrees) comes out at the bottom with warmer air going in at top.
  5. 080104@12:00 39 degrees w/65 porch
  6. 080125@11:00 32 degrees w/70 porch
  7. An hourly recording of temperature changes.
    time out in difference
    08:30 35 38


    09:00 38 49


    09:30 38 54


    10:00 41 61


    10:30 42 64


    11:00 42 67


    11:30 44 68


Using cheap roll up shades painted flat black (total cost for five shades and paint was $25 in 2007). Here they are drying in the basement. Took about two hours to paint using a roller and a quart of paint (in lower right hand corner of picture). Use spray paint only if you want to spend a lot of time and money.

These are the two shades on  the south side of porch. Three face the east.

Shades are also present on several south- and west-facing windows on both mainfloor and basement.