Energy is a limited resource; at least in the forms we are now using to produce it. Gas, petroleum, oil, and coal are very expensive, quickly running out, and costly to the environment. We need to look at alternative sources of energy to heat our homes and water, and to run our appliances. Given the sun’s incredible output of solar rays, why not harness this abundantly free resource rather than strip our land of an already limited commodity?What is passive solar heating?
Passive solar technologies convert sunlight into usable heat, cause air movement for ventilation or cooling, or store heat for future use, without the assistance of other energy sources. The term passive indicates that no additional mechanical equipment is used. All solar gains are brought in through windows and minimum use is made of pumps or fans to distribute heat or effect cooling. Technologies that use a significant amount of conventional energy to power pumps or fans are classified as active solar technologies.Advantages of passive solar heating
Passive solar systems have little to no operating costs, low maintenance costs, emit no greenhouse gases, and save energy. Solar energy is a renewable resource and, unlike fossil fuels, is available just about everywhere on earth. Solar energy is free, immune to rising energy prices, and can be used in many ways – to provide heat, lighting, mechanical power and electricity.Disadvantages of passive solar heating
Overheating presents one of the biggest challenges, but this can be controlled by careful planning and construction. For example, roof overhangs can be used to provide shading of the windows during the hot summer months.
Another way to control overheating and extend warm conditions is the use of heavy mass materials in the walls and floors. Quarry tile or stone on floors in a mortar bed, and one Wythe of brick or double layers of gypsum board on walls, will absorb solar radiation, smooth out the peaks of solar gain, and slowly radiate heat back into the room when the sun is gone.How to harness passive solar heating
Choose windows with a higher or even positive energy rating. Place windows predominantly on the south side and as few windows as possible on the east and west sides of a building to prevent overheating. High performance windows, with insulated frames, multiple glazing, low-e coatings, insulating glass spacers and inert gas fills, can reduce heat loss by 50 to 75 per cent.
High efficiency windows, together with R-2000 levels of insulation and air-tight construction, allow passive solar heating to cover a large proportion of heating needs. With the heat contained, often a simple ceiling fan or a forced air furnace fan is all that is required for heat distribution. Up to 25 per cent of a building’s heating requirement can be gained with passive solar techniques.
Some solar homes use a centrally located masonry wood heater to store heat. The bricks and stones surrounding the firebox absorb the solar gain or heat from short but intense firings and slowly radiate it into the room.
You can build your own passive solar heating device. All you need is a relatively small collection of aluminum cans painted black and drilled with some holes, stacked, and then put in a box. Air coming out of the box is fifteen degrees warmer than air going into the box. You are then free to direct such warm air to anywhere it’s needed. And with just a little bit more work, this exact same design could be a passive water heater.
The Middle East and Japan have been utilizing the sun’s energy for years. Used commonly in Israel, a dude shemesh (sun water heater) is a simple contraption where water from a tank is pumped into pipes coated with a black collecting surface. The black panels of the dude attract sunlight and become hot. The pipes transfer this heat over to the water, which runs back into the water tank. A half-hour pulse of electricity is all that is needed to heat the tank for a shower or doing the dishes.
Whether you build one yourself or hire professionals to install the needed equipment, passive solar heating is an option that is available to all of us. A passive solar heating design guide can be obtained from The Canadian Mortgage and Housing Corporation (CMHC) at www.cmhc.ca.