Passive solar design must be integrated into a project at the beginning of the design process. It can be incorporated into remodels in the form of room additions with a southern exposure or into a new construction project. It works in all climates to both heat the home in the winter as well as keep it cool in the summer. It is so effective that we have had clients that have not turned their furnace on since we built their homes thirty years ago! It was used by the Greeks, Romans and hundreds of cultures over thousands of years.
Passive solar is not mysterious. It is simply the proper use of the building’s orientation, glazing, thermal mass, insulation, shading and natural ventilation which must be planned during the design stage. Careful attention is paid to the summer and winter sun paths and roofline overhangs to allow sunlight to heat the home’s interior thermal mass in the winter and prevent overheating in the summer. Calculations are performed to verify the amount of mass and glazing needed to heat and cool the home through a typical season. To prevent overheating in the summer, the thermal mass in the home helps keep the interior temperatures cool. This works more effectively that you might imagine. We have even had people comment on how well the “air-conditioning” was working to keep the home below 78 degrees when it was 98 degrees outside – except there was no air-conditioning. The house just stays that cool!
With passive solar design, attention is also paid to prevailing winds and natural convection that facilitate this cooling effect in the summer. By insulating beyond code requirements, heat loss or gain is minimized and stable interior temperatures are achieved with minimal back-up heating or cooling. When heating and cooling is required, the systems can be downsized significantly, and they are rarely used.
Surprisingly, passive solar design adds only marginally to the cost of construction. While it may add to the total cost of construction (depending on design features and site conditions), it can save the homeowner enormously in energy costs. Generally, the homeowner that incorporates passive solar design into their project will recoup the full investment within a few years and they will continue to enjoy the energy savings for the life of the building! If a passive solar design saves you the typical $2,000 per year in energy costs, this amounts to a savings of $100,000 over fifty years without accounting for projected increases in energy costs!
Minimum Ventilation Requirements (MVR), established by ASHRAE and BPI, require that a home has a minimum ventilation of .35 air-changes per hour. Most homes are so leaky that they achieve this standard without any ventilation. Because we build a tighter building envelope to minimize heat losses, we must also pay close attention to meeting this minimum ventilation requirement. During extremely hot or cool days, people tend to close all of the windows to minimize thermal losses. During such weather, a device called a heat recovery ventilator or HRV can be used to assure minimum ventilation requirements are met without the usual heat loss. An HRV is simply a balanced ventilator that pumps air out of the house at the same rate that it pumps air in, but it uses a heat exchanger to preheat or cool the incoming air with the outgoing exhaust air – a great way to get fresh air without heat loss or gain.
Ventilation can also be achieved passively by the use of carefully placed openings such as skylights and windows, which create a passive chimney or convection effect, allowing you to use nighttime cooling during the hot summer months to cool your mass.
For more information, please contact Turko Semmes at email@example.com.