User Manual

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4.3.2. Factor-based calculation procedure of the BACS impact on the
energy performance of buildings (BACS factor method)
General
The BACS factor method described here has been established to allow a simple calculation of the
impact of building automation, control and management functions on the building’s energy
performance. The following figure illustrates how to use this approach.
Remarks
Arrows (( ) illustrate only the calculation process and do not represent energy and/or mass flows
1) Delivered energy is the total energy, expressed per energy carrier (gas, oil, electricity etc.)
a) Thermal energy = overall energy use for heating, DHW, cooling, and ventilation
b) Electricity energy = overall energy use for auxiliary equipment and lighting
c) Specific energy use for heating, DHW or cooling
d) Specific energy use for auxiliary equipment or lighting
The BAC factor method gives a rough estimation of the impact of BACS and TBM functions on
thermal and electric energy demand of the building according to the efficiency classes A, B, C and D.
The BACS factor method is specially appropriated to the early design stage of a building because
there is no special information needed about any specific control and automation function just the
recent (if it is an existing building) or reference building automation class and the classification of the
building as expected or predefined.
Simplified calculation method
The BACS efficiency factors were obtained by performing dynamic pre-calculations for different
building types. Thereby each building type is characterized by a significant user profile of occupancy
and internal heat gains due to people and equipment, respectively. The BAC efficiency classes A, B,
C and D were represented by different levels of control accuracy and control quality.