Throughout the ages, we have sought to improve the level of comfort offered by our surroundings. In colder regions, we have tried to heat our dwellings and in warmer climates, to cool them down because if we are not comfortable, we can neither work nor relax. But thermal comfort vital to our well being, is subject to three basic influences:
The human factor
our clothing and activity level and how long we remain in the same situation
radiation temperature and surrounding temperature
its temperature, velocity and humidity
Among these influences, the human factor is somewhat unpredictable. The others can be controlled in order to provide that much sought after feeling of well being.
Changing patterns in construction, working practises and internal occupancy levels have created
new parameters within which designers must operate.
Modern buildings for instance, generate far more heat than their predecessors of say, 50 years ago and there are several reasons for this:
Developments in building technology have also given rise to an increased use of glass - even when solar protective glazing is fitted, solar gains can be considerable.
Increasing numbers of occupants, each generating some 120W/h of heat, are routinely stuffed into office areas.
Computers, printers and photo copiers, all part of the modern offices scenario, also generate substantial heat loads.
Many modern shops could be adequately heated by their
lighting alone heat gains in the order of 15-25W/m² are not uncommon in Europe.
Introducing the outside air into a building also introduces its temperature something of a problem if it's 30ºC outside!