Air changes per hour. This can be converted to litres per second and vice versa if you know the volume of your zone.


When air is being cooled, the dew point temperature is the minimum temperature the air can reach before moisture starts to precipitate out of the air and condensation can form.

At this temperature, the air is said to be saturated with water vapor.


Heating, Ventilation and Cooling


Thermal Response Factor

Sometimes known as weighting factors or z-transfer function coefficients, these values describe how the temperature of a space responds to a change in thermal energy. They are essential in Tas Systems for modelling HVAC systems, and are calculated by the Building Simulator.

Unmet Hour

An hour of the year during which the demand for heating/cooling/ventilation is not met. For example, the HVAC system may not have enough heating/cooling capacity to meet the demand for every hour of the year.

Weighting Factor

See thermal response factor