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States. Large areas of radiant surface can be used to offset large losses of bodily radiant heat, as
in the case of large areas of cold glass on a winter day, or when users are both scantily clothed
and sedentary. In summer, such panels can help offset radiant gain from electric lights or large
glass areas. The ceiling is often favored for the panel location, because it is uncluttered by the
furniture, tackboards, and other items that cover floors and walls. At the 56-story Commerzbank
in Frankfurt, Germany, chilled ceilings serve all office floors in conjunction with the ventilation
system.
Green on the Grand (Fig. 10.60) is a 23,465-ft2 (2180-m2) two-story office complex in
Kitchener, Ontario. Its design combines a very highly insulated envelope, daylighting, water
conservation, a gas absorption (non-CFC, non-HCFC) chiller/heater with a heat rejection pond, a
separate IAQ system, and heat recovery of exhaust air. It also features a dedicated air system for
ventilation and a hydronic system for heating and cooling. The hydronic system uses fan-coils
for the entryways and radiant panels on ceilings of office spaces. (The conditioned air in this
example is provided by the ventilating system.) Fan-coils are better able to handle the extremes
of entryway heat losses and gains. The radiant panels in the offices are used for both heating and
cooling, but are sized to meet cooling loads and cover 30% of the ceiling area. Tenants were
given their choice of two designs: steel panels suspended below a drywall ceiling (painted to
match the ceiling color) or extruded aluminum panels fit into a suspended ceiling system. To
prevent condensation on these radiant panels during cooling, the ventilation air is dehumidified.
The ventilation system supplies low on the walls and exhausts high on the walls, a form
of displacement ventilation. There are two rates of fresh air: 20 cfm (10 L/s) per person, and
(when economizer cycles operate or when more fresh air or more cooling is required) 40 cfm (20
L/s) per person. The exhaust air then flows through two heat exchangers: the first reheats fresh
air that has been greatly cooled for dehumidification; the second preconditions the incoming
fresh air at the point of entry. The latter heat exchanger is a rotary-wheel ERV capable of
transferring both heat and moisture.
Several approaches to the radiant cooling (and heating) panel, independent of a
dehumidified air supply, are shown in Fig. 10.61. These approaches assume a minimal
floor/ceiling thickness, which could contribute either to reducing the floor-to-floor height or to
greater ceiling height (for daylight penetration or displacement ventilation). If a raised floor is
used above these concrete slabs, even higher percentage heat gains come from the ceiling.
Fig. 10.61 Approaches to radiant cooling systems. (a) Concrete core system: water is
circulated through plastic tubes embedded in the concrete floor/ceiling slab. (b) With
carpet, pad, and insulation on the floor, most of the heat radiates to the ceiling. (c) Panel
system, usually using aluminum facing, connected to metal tubes. (d) Panel system has the
highest percentage of heat to the ceiling. (e) Cooling grid made of capillary tubes embedded
in ceiling plaster (or in gypsum board or mounted on ceiling panels). This is the most even
surface temperature distribution. (f) Again, a high percentage of the heat is radiated to the
cooled ceiling, depending on the use of insulation below the carpet and pad. (From Center
for Building Science News, Fall 1994. Lawrence Berkeley Laboratory, CA.)
Radiant cooled floors are sometimes used, as in the Bleshman Regional Day School (Fig.
10.62). The designers of this school for the handicapped recognized that the majority of its users
would spend much of their time quite close to the floor and that the colder air near the floor