Annex VIII Calculation of the specific energy consumption requirement

The specific energy consumption SEC is calculated with the following equation:

where:

• SEC is Specific Energy Consumption for ventilation per m² heated floor area of a dwelling or building [kWh/(m².a)];

• t_a is annual operating hours [h/a];

• pef is primary energy factor for electric power generation and distribution [-];

• q_net is net ventilation rate demand per m² heated floor area [m³/h.m²];

• MISC is an aggregated general typology factor, incorporating factors for ventilation effectiveness, duct leakage and extra infiltration [-];

• CTRL is ventilation control factor [-];

• x is an exponent that takes into account non-linearity between thermal energy and electricity saving, depending on motor and drive characteristics [-];

• SPI is Specific Power Input [kW/(m³/h)];

• t_h is total hours heating season [h];

• ΔΤ_h is the average difference in indoor (19 °C) and outdoor temperature over a heating season, minus 3K correction for solar and internal gains [K];

• η_h is the average space heating efficiency [-];

• c_air is the specific heat capacity of air at constant pressure and density [kWh/(m³ K)];

• q_ref is the reference natural ventilation rate per m² heated floor area [m³/h.m²];

• η_t is the thermal efficiency of heat recovery [-];

• Q_defr is the annual heating energy per m² heated floor area [kWh/m².a] for defrosting, based on a variable electric resistance heating.

  $Q_{\mathrm{defr}}=t_{\mathrm{defr}}\times {\mathrm{\Delta {\rm T}}}_{\mathrm{defr}}\times c_{\mathrm{air}}\times q_{\mathrm{net}}\times \mathrm{pef}$ ,

  where

  • t_defr is the duration of defrosting period, i.e. when the outdoor temperature is below – 4 °C [h/a], and

  • ΔΤ_defr is the average difference in K between the outdoor temperature and – 4 °C during the defrosting period.

  Q_defr applies only to bidirectional units with recuperative heat exchanger; for unidirectional units or units with regenerative heat exchanger is Q_defr = 0.

SPI and η_t are values derived from tests and calculation methods.

Other parameters and their defaults are given in Table 1.