User Manual

103
BACS efficiency factors
The impact of BACS functions from an energy class on a building's energy demand is established
with the aid of BACS efficiency factors. The BACS efficiency factor for all building models is in
the reference class C = 1 (energy demand = 100 %):
BAC efficiency factor = energy demand BAC
planned class
/ energy demand BAC
Class C
BACS efficiency factors for all building models are published in the table from EN 15232.
Energy savings from BACS functions
Energy demand for BACS efficiency class C must be known (calculated using the detailed calculation
method, measures or possibly estimated) to establish energy savings from BACS functions for a
BACS efficiency class:
Energy demand BAC
planned class
= energy demand BAC
class C
* BAC efficiency factor
planned class.
Savings = 100 * energy demand BAC
class C
(1 – BAC efficiency factor
planned class
) [%]
Benefits and limits of the simplified method
The simplified method allows you to determine the impact of BACS and TBM on the energy efficiency
of a number of buildings to a satisfactory degree without costly calculations.
As a rule, BACS efficiency factors can be used on two basic types:
· Relative to unknown energy demand in class C
BACS efficiency factors are scalable. You determine the energy demand for a building in a given
energy efficiency class in relationship to the energy demand of a building in energy efficiency
class C.
This allows for a sufficiently accurate determination of energy savings in [%] versus class C
· Relative to known energy consumption in class C
When annual absolute energy demand for a building in class C is known (e.g. energy
consumption was recorded or measured over three years of operation, or the planner calculated
or possibly estimated the energy demand), you can easily and sufficiently determine the absolute
energy savings (e.g. in [kWh]) for a building in a certain energy efficiency class in relationship to
a building in energy efficiency class C.
You can also calculate savings from energy costs and the payback period for updating BAC by
applying current costs per [kWh].
Application of the simplified method is limited to BAC efficiency classes A, B, C and D. A more finely
graded classification of the BAC functions is not possible using this method.