Passive solar is a building design approach that incorporates certain materials into the roof, walls and floors that collect solar energy to heat a home in the winter, cool it in the summer, and heat water year-round. It’s called passive because it requires no electric devices or mechanical devices to operate and performs various functions.
This is not about collecting solar energy through dedicated solar panels to generate electricity. It’s about temperature management. In its simplest form it involves the use of windows with a southern exposure that simply allow the sunlight to enter the home in winter, and are shaded with blinds or window shades in the summer. Many people take advantage of that sunlight by installing special, thermal tiles in their floors to absorb the heat during the day, and release it slowly during the night. There are also wall panels that perform the same function. Certain types of floor tiles and wall boards collect the heat.
You have to be able to shade windows in summer. Otherwise, you can get something referred to as passive/aggressive solar heating. The result is a house that is too hot during the day, especially in summer. You want that “Goldilocks” factor, where the temperature is just right. Shades and shading can help you manage variable heat and sunlight conditions.
Hot Water Heating With Solar
A rooftop set-up for hot water heating involves a series of tubes encased in a black box on the roof and covered with a sheet of glass or plastic. The sunlight enters the black box through the glass and heats the interior to allow the enclosed water to heat.
Often, there is a tank above the arrangement that allows the hot water to rise into the tank, and the water is drawn by gravity down into the house. The temperature varies depending on the amount of sunlight and the ambient temperature outside, but the water can range from hot to warm with no effort, other than pumping cold water up into the tank.
Southern Exposure Is Necessary
The key to successful use of passive solar is the orientation of the home, its windows and the rooftop solar water heater. An unobstructed, southern exposure is ideal for heating, in addition to generous windows both in size and number.
It’s not just about staying hot in the winter, but also about staying cool in the summer. There’s one simple solution: trees. Trees have leaves in the summer to shade a home, and they lose their leaves in the winter if you live in a temperate zone. The result is that sun passes through the bare branches of trees in winter, and is blocked by the leaves of summer.
There are also ceramics that absorb cooler temperatures at night and continue to cool during the day. It’s the old thermos joke: “How do it know?” Many solar tiles have this characteristic.
There are some simple and remarkable DIY projects and even new technologies that allow you to cook a variety of meals with solar power. The critical success factor is bright, direct sunlight focused directly into the solar oven. Once again, these are passive solar approaches that require nothing more than direct sunlight to effectively function.
Insulate, Insulate, Insulate
Any passive solar heating set-up assumes that you are going to collect and release heat. What’s essential is to contain the heat in a properly insulated structure. It’ s easy to get complacent, especially if you have a high-efficiency wood-burning stove blasting out the heat. But passive solar is different. The heat that is collected and stored will vary depending on cloud cover and time of year. Unfortunately, winter months have the shortest duration of sunlight when we need it most.
As a result, high-efficiency insulation is critical. This is especially true around door frames, windows and electrical outlets facing the outside. The idea is to trap and collect heat, and insulation will give you a better chance to do that.
Have you heated your home with passive heat? What advice would you add? Share it in the section below: