Division (2) Global costs for buildings and building elements shall be calculated by summing the different types of costs and applying to these the discount rate by means of a discount factor so as to express them in terms of value in the starting year, plus the discounted residual value as follows:

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C_{g} (τ) = C_{I} \underset{j}{+ Σ} [Σ_{i =1}^{τ} (C_{a,i} (j) \times R_{d} (i)) - V_{f,τ} (j)]

where:

means the calculation period

C_g(τ)

means global cost (referred to starting year τ ₀) over the calculation period

C_I

means initial investment costs for measure or set of measures j

C_a,I (j)

means annual cost during year i for measure or set of measures j

V_f,τ (j)

means residual value of measure or set of measures j at the end of the calculation period (discounted to the starting year τ ₀).

R_d (i)

means discount factor for year i based on discount rate r to be calculated

as:

R_{d} (p) = {(\frac{l}{l + r /100})}^{p}

where p means the number of years from the starting period and r means the real discount rate.