Sit with us at the table as we ask two experts how we consumers can benefit from passive solar design. Their answers to OurHouse questions are a bit more involved than coffee conversation.
Host: Tish Leizens, Publisher & Editor
Dr. William Makofske, Professor
Professor of Physics, Emeritus, Ramapo College, N.J. and an active member of Sustainable Warwick in New York. Dr. Makofske has designed his own near-zero net energy house in Warwick that has been on the National Solar Tour for the past several years.
Richard Pedranti, Architect
LEED (Leadership in Energy and Environmental Design) accredited professional and member of the U.S. Green Building Council. Pedranti, a native of Pike County in Pennsylvania, owns a firm under his name and is a licensed architect in the tristate area.
OH: What is passive solar design?
Richard Pedranti: Passive solar design is using the energy from sunlight to control the thermal comfort of the built environment without the use of energy-consuming mechanical components like pumps and fans. The design relies on the positioning of building elements and spaces to accept and manage the solar radiation provided by the sun.
Dr. William Makofske: The use of south windows, greenhouses, sunspaces, clerestories or other passive collectors to gain solar heat for a dwelling in the winter. More broadly, it should incorporate good design that provides useful daylight and heat to spaces that are used during the day.
OH: What is passive solar design?
Richard Pedranti: Passive solar design is using the energy from sunlight to control the thermal comfort of the built environment without the use of energy-consuming mechanical components like pumps and fans. The design relies on the positioning of building elements and spaces to accept and manage the solar radiation provided by the sun.
Dr. William Makofske: The use of south windows, greenhouses, sunspaces, clerestories or other passive collectors to gain solar heat for a dwelling in the winter. More broadly, it should incorporate good design that provides useful daylight and heat to spaces that are used during the day.
OH: How can you apply a passive solar design on a new home?
RP: The fundamental concepts in designing a new passive solar home include: orienting the building to face the equator, extending the building dimension along the east/west axis, sizing the windows to face the midday sun in the winter and be shaded in the summer, minimizing windows on other sides—especially western windows, including correctly-sized, latitude-specific overhangs, or shading elements, and using the appropriate amount and type of insulation. The precise amount of equator-facing glass should be based on careful consideration of latitude, altitude, and climatic conditions.
WM: The long side of the home should be oriented south, and daytime lived-in rooms should get most of the heat and daylight. It is best to apportion the amount of window to the size of the room to avoid overheating. A general rule of thumb is to have the total glass area between 8 percent to 12 percent of the total floor area of the house.
If the glass area is less than 10 percent, you don’t have to worry about overheating. If it is between 10 percent to 12 percent then you must have an additional way of storing excess heat. Heat is normally absorbed well by tile or concrete floor.
OH: What about on existing homes?
RP: Strategies include the use of landscaping that screens unwanted summer sun yet allows for winter sun, retrofitting existing windows with window coverings, either manual or motorized, and adding more insulation to the exterior envelope of the building.
WM: You should first weatherize your house to minimize your heat loss. You then can add windows to the south side if appropriate. Add a greenhouse or sunspace, which often use small fans to increase warm air movement into the house during the peak collection hours. Another approach is to consider adding solar air collectors to the south side of the house. These will cycle warm air into the house on sunny days but not lose extra energy from the house at night.
OH: How does passive solar design benefit the consumer?
RP: Most importantly, the use of passive solar design increases thermal comfort without the need to use nonrenewable natural resources such as oil and gas. Therefore, it saves the homeowner money. Another benefit is the increase in the use of natural light to daylight the interior. Increased day lighting results in more pleasing indoor environment and reduces the need for artificial lighting. The reduction in artificial lighting reduces the electrical load. Carefully considering the placement of operable windows in passive solar design can also provide for natural ventilation of the indoor spaces in the summer months.
WM: For a new house, passive solar is often a no-cost option when you build. You don’t use more windows; you just put more on the south side, and less on the other sides. A simple rule of thumb is that each square foot of south window will gain about 100,000 BTUs over the heating season, replacing a gallon of oil burned at 70 percent efficiency. Two hundred square feet of south window will save that many gallons of oil every year over the lifetime of the house. On a sunny day, a well-designed passive solar house can heat adequately all day, and provide enough nighttime stored heat to get to the next day. For existing homes, oil reduction will be similar, but there will be extra cost to retrofit the passive solar feature.
For more information on this topic, email our resource guests directly.
Dr. William Makofske at makofske@warwick.net.
Richard Pedranti at richard@richardpedranti.com.
If you want OurHouse to discuss other topics in this educational forum,
email Tish Leizens at tish@ourhousepublications.com.
