Solar Energy and Home Design

Many of our clients are interested in and ask us about energy conscious design of homes and “solar” design. Using the sun to make buildings more comfortable is a strategy dating back thousands of years. Making wise choices about where we build and how we build makes sense and is ecologically responsible.

Three terms we often use to refer to solar design are:

Solar tempered:

Spaces that take advantage if the sun's energy by their form, their orientation to the south, and the size and location of windows.

Passive solar:

Systems that collect, move, and store heat using natural heat-transfer mechanisms such as conduction and air convection currents. Design of homes that use passive solar energy includes appropriately sized south-facing windows and the thermal mass such as concrete.

Active solar:

A system using mechanical devices (pumps, fans, photovoltaic cells, etc.) that transfers collected heat to the storage medium or the end-use.

Below is a more extensive glossary of terms that you might encounter in energy conscious design discussions. We have found them in Brown. G.Z.: Sun, Wind, and Light - Architectural Design Strategies. New York: John Wiley & Sons, 1985. ISBN: 0-471-895067

Attached Sunspace:

A room that doubles as a solar collector; also called attached greenhouse, solarium. The term attached also implies a space that shares one common wall with the associated building.

Conductance:

A measure of the rate of heat flow between two surfaces, measured in BTU per hour per degrees Fahrenheit, per square foot of material that separates the two surfaces. (BTU per hr. per F° per sq. ft.).

Direct Gain:

The transmission of sunlight directly into the space to be heated, where it is converted to heat by absorption on the interior surfaces.

Direct Radiation:

The component of solar radiation that comes directly from the sun without being diffused or reflected.

Glare:

A very bright light or a high contrast of light making it uncomfortable or difficult to see.

Glazing:

Transparent or translucent materials, usually glass or plastic, used to cover an opening without impeding the admission of heat and light.

Heat Gain:

The gross amount of heat that is introduced into a space, whether from incoming radiation or from internal sources such as occupants, lights, and equipment.

Indirect Gain:

The transfer of solar heat into the space to be heated from a collector that is coupled to the space by an uninsulated, conductive, or convective medium; for example, thermal storage walls and roof ponds.

Insulation:

Low mass material with high thermal resistance used to slow the transfer of heat by conduction.

Internal Heat Gain:

Heat generated inside the building by sources other than the space-heating equipment, usually by appliances, lights, and people.

R-value:

A measure of the thermal resistance of a building element; the reciprocal of the U-value. See thermal resistance.

Solar Aperture:

That portion of the solar wall covered by glazing. The orientation of the opening should be within 30 degrees of south to be considered a solar aperture.

Solar Radiation:

Radiation emitted by the sun including infrared radiation, ultraviolet radiation, and visible light.

Thermal Radiation:

Energy transfer in the form of electromagnetic waves from a body by virtue of its temperature, including infrared radiation, ultraviolet radiation, and visible light.

Thermal Resistance:

A measure of the insulation value or resistance to heat conduction of building elements or materials; specifically, the reciprocal of the thermal conductance, also called R-value.

Thermal Storage Mass:

High density building elements such as masonry or water in containers, designed to absorb solar heat during the day for release later when heat is needed.

Trombe Wall*:

masonry thermal storage wall placed between the solar aperture and the heated space. Heat is transferred into the space by conduction through the masonry and, if vents are provided, by natural convection.

U-Value:

A measure of heat flow, specifically, the number of BTU's that flow through one square foot of building skin, in one hour, when there is a 1 degree difference in temperature between the inside and outside air, under steady state conditions. The U-value is the reciprocal of the resistance or R-value.

*Note: Do not try to figure out what it means. It is the last name of the Frenchman who first used the system in 1966.