Comfort temperature: Flawed status in the CIBSE Guide

It is shown qualitatively and quantitatively that it is invalid to place the room comfort temperature tc on the conductance ΣAh 2 as is done in the model for room heat exchange in the 1986 CIBSE Guide. It is noted that the global value of comfort temperature Tc in a room is a low-conductance combination of the room air and radiant temperature while the temperature index T i combining these measures in relation to bulk heat transfer is a high conductance construct; T and T i cannot be represented simultaneously in a thermal circuit. Thus the Guide's use of segments of ΣAh a and the factors F 1 and F 2 in the expression for the room heat Qt are not logically sustainable.