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Passive Heating and Cooling
A house in Michigan can generate 75% of the energy needed for heating in a given year
by passive means alone! By paying attention to natural energy flows, a homeowner can
significantly downsize HVAC equipment, and obtain free solar energy to heat their house, These
are the major methods used to passively heat a house:
- Orientation and siting of a house for maximum South-side glazing combined with large overhangs on the roof of the house. In the winter, the sun has a lower angle and will warm the interior surfaces of the house (hopefully with good quality, low-e windows), while in the summer, the overhangs will shade the windows from solar gain.
- Minimal North side glazing - this will keep insulation R-values higher on the North side where windows offer no energy gain, but do allow heat to be transferred more efficiently.
- Winter heating becomes much more effective with high mass surfaces that absorb the sun's energy during the day and radiate it into the house at night. Installation of interior concrete subfloors (suitable for radiant heat systems) or Trombe Walls are effective for soaking up solar energy.
- We achieve passive cooling by installing or retaining trees strategically on the lot, usually on the East, West, and North sides. Since solar gain can have a great effect from the East and West during the summer with no way to protect window with overhangs, the decidous trees can effectively shade the house from heat gain. Likewise, Northern evergreen tree placement can shield the house from cold winter winds, decreasing the heating loads.
- Once proper shading is in place, techniques such as whole house fans and other air flow management systems can take advantage of natural cooling to significantly reduce air conditioner use.
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