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ABB i-bus® KNX
Heating, Ventilation and Air Conditioning –
Influencing Variables on Room Climate

Influencing Variables on Room Temperature Influencing Variables on Air Quality

Internal and external factors have an effect on the thermal The indoor climate in living and working areas has a scien-
conditions in a room or a building. As an external factor the tifically proven impact on health, job performance and
solar radiation is important for the indoor temperature – well-being of people. A suitable indicator for determina-
particularly with regard to modern architecture with glass tion of the room air quality is the CO 2 concentration. In ad-
fronts. Besides this, the room temperature is strongly af- dition the values for room temperature and air humidity
fected by the exchange of thermal energy through windows must be controlled to meet the requirements for a com-
and walls as well as the loss of thermal energy through open fortable room climate.
doors and windows.
Studies have shown, that high CO 2 concentration in the air in-
Depending on the intensity, all this interactions influence fluences the well-being as well as the performance and
also the energy efficiency of a building and have therefore to learning ability of people. Besides the normal CO 2 concen-
be optimised. tration in the air, human respiration is an important factor
Internal thermal inputs from lighting, devices or persons increasing the CO 2 concentration in a room. Therefore it is
have also an influence on the room climate. By planning a important to measure the CO 2 concentration in rooms where
heating, ventilation or air conditioning system all this inter- many persons are present (schools, conference rooms, open-
nal and external factors have to be considered. plan offices). Monitoring of thresholds enables fans to be
switched via ABB i-bus® KNX allowing automatic control of
the CO 2 concentration and sufficient supply of fresh air.

Loss of thermal energy Exchange of thermal energy
through open doors through windows and walls
Thermal input from
CO 2 14
sun, lighting, persons
and devices