This European Standard is part of a series of standards on the method for calculation of system energy requirements and system efficiencies of space heating systems and domestic hot water systems. The scope of this specific part is to standardise the: required inputs; calculation method; resulting outputs; for space heating generation by combustion sub-systems (boilers), including control. This European Standard is the general standard on generation by combustion sub-systems (boilers). If a combustion generation sub-system is within the scope of another specific part of the EN 15316 series (i.e. part 4.x), the latter shall be used. EXAMPLE Biomass combustion generation sub-systems are within the scope of prEN 15316-4-7. This European Standard is also intended for the case of generation for both domestic hot water production and space heating. The case of generation only for domestic hot water production is treated in EN 15316-3-3.