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Sun Spaces

Homeowners with a sunspace frequently cite it as their favorite room of the house. Sunspaces provide light, warmth, aesthetics, and a healthy environment for plants and people. Sunspaces can also save money on home heating costs. In fact, well-designed sunspaces can provide up to 60% of a home’s winter heating requirements.

Elements of Sunspaces

Sunspaces contain the following elements:

Glass panels, or "glazing," permit light to enter a room, but prevent infrared heat from escaping. This process warms the interior space.
Thermal mass, such as masonry or water, absorbs heat and releases it into the room during extended cloudy weather or at night.
Insulation in ceilings, walls and windows retard heat loss at night and during cold weather.
Climate control features such as operable windows, vents, and fans keep the sunspace from overheating and move warm air to other parts of the house.

Design Considerations

When designing a sunspace, there are several important factors that must be taken into consideration. Your planned primary use of the sunspace will influence some planning decisions:

[bulletlistA sunspace must face south. Due south is ideal, but 30 degrees east or west of south is acceptable. If the south side of the house faces the street, the sunspace must be integrated into the house to avoid a "tacked-on" look.

The sunspace must receive direct sunlight between the hours of 10:00 a.m. and 3:00 p.m. Any object over 10 feet tall within 15 feet of the south glazing is likely to block solar gain.

If the primary function of the room is to provide heat, you can maximize heat gain by using sloped glazing, few plants, little thermal mass, and insulated, unglazed end walls. However, compared to vertical glazing, sloped glazing loses more heat at night, can be covered with snow in the winter, and can cause overheating in warmer weather. Vertical glazing can maximize heat gain in winter, and yields less heat gain in the summer. A well-designed overhang may be needed to shade the glazing in the summer.

If the space is to be used as a greenhouse, remember that plants require lots of light, fresh air, water, and protection from extreme temperatures. Plants consume energy that would otherwise be available as heat. Plants require overhead glazing, which complicates construction, and glazed end walls, which are net heat losers.

As most homeowners wish to use their sunspaces year-round as living areas, the rooms should be designed to have minimum glare and moderate humidity. Carefully sized thermal mass materials will improve comfort levels by stabilizing temperature extremes.

Adapted from: "Sunspace Basics," by the US Department of Energy’s Energy Efficiency and Renewable Energy Network (EREN). There is other good information on sunspaces on the EREN website. In addition, see the North Carolina Solar Center (http://www.ncsc.ncsu.edu/fact/21sunspc.html) for a comprehensive overview of sunspace design.