Page 356 - Handbook of Energy Engineering Calculations

Devices, by V. and A. Olgyay, available from Princeton University Press.
Passive solar-heating systems should be considered only for tightly
constructed, well-insulated buildings. The cost of a passive system is
generally higher than that of insulating and weatherstrip-ping a building. A
building that has a relatively small heat load will require a smaller collection

and storage system and so will have a lower construction cost. The cost-
effectiveness of a passive solar-heating system is inversely related to the heat
losses of the building. Systems which have a smaller ratio of collector area to

floor area are generally more efficient.
Significant decreases in the size of the collector can be achieved by placing
movable insulation over the collector at night. This is especially
recommended for extremely cold climates in more northern latitudes. If night
insulation is used, cal culate heat loss for the uninsulated collector for 8 hours

with the daytime average temperature and for the insulated collector for 16
hours with the nighttime average temperature.
2
Table 8 is based on a heat loss of 8 Btu/(day · ft ) of floor area per °F
2
[W/(m · K)]. Total building heat loss will increase with the increase in the
ratio of collector to floor area because of the larger areas of glazing.
However, it is assumed that this increase in heat loss will be offset by

providing higher insulation values in noncollector surfaces. The tabulated
values correspond to a residence with a compact plan, 8-ft-high ceilings, R-
30 roof insulation, R-19 wall insulation, R-10 perimeter insulation, double
glazing, and one air change per hour. It is provided for estimating purposes

only. If the structure under consideration differs, the ratio of collector area to
floor area, g, can be estimated for heat-loss calculations by using g = h(65 –
2
2
t )/i , where h = estimated heat loss, Btu/(day · ft · °F) [W/(m · K)].
T
L
o
Passive solar heating is nonpolluting and is environmentally attractive.
Other than the pollution (air, stream, and soil) possibly created in
manufacturing the components of a passive solar heating system, this method
of space heating is highly desirable from an environmental standpoint.
Solar heating does not provide carbon dioxide, as does the combustion of
coal, gas, oil, and wood. Thus, there is no accumulation of carbon dioxide in
the atmosphere from solar heating. It is the accumulated carbon dioxide in the

earth’s atmosphere that traps heat from the sun’s rays and earth reradiation
that leads to global warming.