The ASHRAE Task Group on Energy Requirements developed the general procedure referred to as the transfer function method (TFM). This approach is a method that simplifies the calculations, can provide the loads originating from various parts of the building, and can be used to determine the heating and cooling loads.
The method is based on a series of conduction transfer functions (CTFs) and a series of room transfer functions (RTFs). The CTFs are used for calculating wall or roof heat conduction; the RTFs are used for load elements that have radiant components, such as lights and appliances. These functions are response time series, which relate a current variable to past values of itself and other variables in periods of 1 h.
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