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the room air and the slab, such as in a ventilated concrete slab (Braham,
2000), or in direct slab cooling using outdoor cool air (Chen, Athienitis, and
Galal, 2012). Further cooling reduction can be realized by installing exterior
shading for the north window to prevent unnecessary solar heat gain in the
early morning and late afternoon.
Shoulder Season
The shoulder season (e.g., around September) features mild exterior
temperatures and strong solar radiation on the façade resulting from
relatively low solar altitude angles. Cooling will dominate the space
conditioning energy consumption. Since cool outdoor air is available during
the nighttime for free cooling, the measures described in Section 7.4.3.3 on
summerdesigndayforcooling-dominatedclimatecaneffectivelyreducethe
cooling load and peak demands.
7.4.4 Alternative Design and Operation for Consideration
In addition to the design and operation techniques investigated earlier, here
are some others that could also be adopted.
7.4.4.1 Building-Integrated PV: Optimal use of Building Roof and
Façade
The current RSF design uses a low 10° roof slope (note that the latitude
is 39.7°, so an optimal roof slope would normally be around 40° for solar
energy collection), in part to reduce the cost associated with a high ceiling,
facilitate roof maintenance, and also use the ceiling for radiant cooling/
heating. One possibility in a new design is to optimize the south façade and
roof for solar energy collection. For example, using the current building
form and orientation, a 1 kW PV system on the façade would be expected
to generate about 995 kWh per year as compared to 1253 kWh for the same
could also be combined with heat recovery for solar air heating as described
next.
7.4.4.2 Building-Integrated PV/T and Transpired Collector with
Air-Source Heat Pump
The building roof and façades can be used as substrates for solar thermal
energy collecting systems (e.g., BIPV/T and transpired thermal solar
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