Two types of sunspaces are defined according to the degree of
integration with the rest of the building. One type is the attached
sunspace, whose north wall is common with adjoining rooms and 30-feet wide
in the east-west direction. The other type is the semi-enclosed sunspace
that has three common walls, the north, the east, and the west. The
semi-enclosed sunspaces are 24-feet wide (east-west) and 12-feet deep
(north-south). The north common wall is 9-feet high in all reference
One geometrical shape of the attached sunspace and two of the
semi-enclosed sunspace are treated. The attached sunspace has a single
plane of glazing on the south wall, tilted up from the horizontal by 50
degrees. The two semi-enclosed geometries are: (1) a single, vertical
plane of glazing on the south wall, and (2) a single 50-degree tilted
plane of glazing on the south wall. These three geometrical
configurations are illustrated in figure 27.
The reference designs include two types of common wall between the
sunspace and the adjacent building. One is lightweight and insulated,
corresponding to a frame wall with a thermal resistance of R-20; and one is
uninsulated 12-inch thick high density concrete as used in the direct gain
designs. In the lightweight wall configuration, there is a row of water
containers in the sunspace for thermal storage. The row extends the full
east-west width of the sunspace. The containers are twice as high as they
are deep. The water volume is 1 ft3/ft2 of common wall area. The
containers are on the sunspace floor immediately adjacent to the common wall
through the sunspace air.
Both wall configurations include thermocirculation vents in the common
wall whose areas total 6 percent of the north wall area. The vent centers
are separated by a height of 8 feet. There is no reverse thermocirculation.
For each geometry and wall configuration, movable insulation may or may
not be applied at night to the sunspace glazing. When used, the night
insulation has a thermal resistance of R-9 and is in place from 5:30 p.m. to
7:30 p.m. solar time. The end walls of the sunspace are insulated to R-20
and have no glazing.
The sunspace floor is a 6-inch thick slab of masonry material with a
thermal conductivity of 0.5 Btu/deg.F-ft-hr and a volumetric heat capacity
of 30 Btu/ft3. There is conduction through underlying soil to a fixed
temperature deep in the earth and through perimeter insulation to the
The surfaces of the common wall on the sunspace side have solar
absorptance of 0.7 if they are lightweight and 0.8 if they are masonry. The
water containers have a solar absorptance of 0.9. The sunspace floor has a
solar absorptance of 0.8. The other surfaces (ceiling and end walls) have
solar absorptance of 0.3.
A sunspace infiltration rate of 0.5 air changes per hour is assumed in
all reference designs. Auxiliary heating prevents the sunspace temperature
from falling below 45deg.F and ventilation is assumed to limit the maximum
sunspace temperature to 95deg.F if possible.