Using Passive Solar Design to Reduce Energy Bills


By Brett Reilly

Summer is over, the temperatures are dropping and there are fewer hours of sunlight in each day but even with fewer hours of sunlight it is still more than enough to heat a home and generate energy. Sunlight can be harnessed in the fall and winter to heat homes or any building. The sun will have fewer hours in the sky this time of year but it will be enough to generate substantial electricity through photovoltaic (PV) panels.

This technique of capturing heat from sunlight in the colder months of the year is called passive solar design. The idea has been used for a millennium and dates back to the ancient civilizations of the Aztec, Greek, and Chinese. The ancient Greek philosopher Aeschylus wrote: “Only primitives & barbarians lack knowledge of houses turned to face the Winter sun.”

Technically speaking passive solar design has five elements; aperture, absorber, thermal mass, distribution, and control. What this means is that direct sunlight enters a building through window glass (aperture); heats and stores the heat in parts of the building that are dark and solid like tile floors and granite countertops (absorber, thermal mass); the heat circulates (distribution); and extended eaves shade the aperture in the summer time (control).

For passive solar design to work the windows need to be facing south and cannot be shaded by trees or other buildings. A great example of passive solar design is the No Energy Bill model built by Tapa Homes, located in Milford. The back of the home features a wall of windows, two foot eaves, and no obstruction of the winter sun. The inside of the home has dark hardwood floors, dark granite countertops, and knee walls strategically placed to act as an absorber and thermal mass. The fans in each room control the heat by cooling in summer and moving the heat around the house in the winter.

The No Energy Bill model home has a 4 kilowatt array of PV solar panels that has produced more that 6,000 kilowatt hours in the last year. PV solar panels absorb solar radiation which is converted into electricity. The sun light can be direct or indirect; as long as the sun shines the panels will make electricity. Cloudy days and rainy days only reduce the amount of electricity produced; not stop it.

The combination of passive solar design, PV solar panels, and other efficiencies can drastically reduce electricity usage, lower and even reduce energy bills. Civilizations from thousands of years ago were able to keep their homes warm in the winter without electricity or burning fossil fuels like oil, propane, coal, or natural gas. They understood the power of the sun and the principles of passive solar design. It is very easy to incorporate these principles in today’s building design with little or no additional costs. The sun can also help energize our homes directly with the use of PV solar panels. Every year the cost of electricity goes up and the cost of PV solar panels go down. It will not be long before everyone can benefit from both of these great technologies.