Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 417

for roof and intermediate ceiling slabs. Pipes are spaced at 15 cm (6 in.),
center-to-center, following the flute spacing of the deck.
Fig. 7.51 Cross-section of the raised floor and the hydronic radiant slab
The ceiling slab temperature is controlled by regulating the valve open
timebasedonthetemperaturedifferencebetweentheroomheating/cooling
setpoint and the actual sensed room temperature using a
pulse-width-modulation control (essentially proportional control). The
open time is linearly related to the temperature difference - 20 min for 2 °C
temperature difference, and zero minutes for zero temperature difference.
Occupants are allowed to modify the programmed setpoint by ±0.5 °C -
these are the only two values provided on the thermostat of each thermal
zone ( Figure 7.53 ) .
In heating mode, the supply hot water temperature to the ceiling slab is
regulatedatabout40.5°C(105°F)bymixingreturnhotwaterwithhotwater
supplied from the boiler. The boiler supply temperature ranges between 42
and 58 °C.