# Commission Delegated Regulation (EU) No 1254/2014 of 11 July 2014 supplementing Directive 2010/30/EU of the European Parliament and of the Council with regard to energy labelling of residential ventilation units (Text with EEA relevance), Division 1: The specific energy consumption (SEC) is calculated using the following equation:

Extent: E+W+S+N.I.

SEC = t a × pef × q net × MISC × CTRL x × SPI − t h × ΔΤ h × η – 1 h × c air × q ref − q net × CTRL × MISC × 1 − η t + Q defr
where:
SEC is the specific energy consumption for ventilation per m2 heated floor area of a dwelling or building [kWh/m2.a];
ta is annual operating hours [h/a];
pef is the primary energy factor for electric power generation and distribution [-];
qnet 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 the 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)];
th is total hours heating season [h];
ΔΤh is the average difference in indoor (19 °C) and outdoor temperature over a heating season, minus 3 K correction for solar and internal gains [K];
ηh is the average space heating efficiency [-];
cair is the specific heat capacity of air at constant pressure and density [kWh/(m3 K)];
qref is the reference natural ventilation rate per m2 heated floor area [m3/h.m2];
ηt is the thermal efficiency of heat recovery [-];
Qdefr is the annual heating energy per m2 heated floor area [kWh/m2.a] for defrosting, based on a variable electric resistance heating.
Q defr = t defr × ΔΤ defr × c air × q net × pef ,
where:
tdefr is the duration of the defrosting period, i.e. when the outdoor temperature is below – 4 °C [h/a]; and
ΔΤdefr is the average difference in K between the outdoor temperature and – 4 °C during the defrosting period.
Qdefr applies only to bidirectional units with recuperative heat exchanger; for unidirectional units or units with regenerative heat exchangers, Qdefr = 0.
SPI and ηt are values derived from tests and calculation methods.
Other parameters and their defaults are given in Table 1. The SEC for label classification is based on the ‘average’ climate.

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Source: https://www.legislation.gov.uk/eur/2014/1254/annex/VIII/division/1 (the official version)
Page: https://openlegislation.uk/eu-regulation-2014-1254/annex-VIII/division-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.