Though several of the indices can not be
represented easily with "off-the-shelf" equipment,
operative temperature is one that is within reach of all
projects. In our opinion for thermal comfort control, the most
suitable arrangement would be a
radiant based system controlled by
operative temperature in parallel with a
dedicated outdoor air system of which
humidity is just one element of the control strategy for
conditioning the air. Operative temperature
thermostats are commercially available or the value can
be presented by a matrix of embedded sensors for
measuring surface temperatures and integrated with the
dry bulb temperature for operative values.
Incidentally, one of the persistence
errors in literature when it comes to the graphical
method of thermal comfort using the
ASHRAE
Standard 55 psychrometric chart is taking the x-axis
as dry bulb temperature when in fact it is operative
temperature. There are circumstances where dry
bulb temperature equals operative temperature but this
(again in our opinion) only occurs in high performance
buildings or what we would classify as a
Type 4 structure and where the met rates, clo
values, humidity and air speeds fall within the
graphical comfort zone.
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