Conservation of fuel and power: Approved Document L, Volume 1 — Dwellings

O N L I N E V E R S I O N L1(b), L2 Existing dwellings 6.21 When connecting an existing dwelling to an existing district heat network or community heating system, the carbon intensity and primary energy of the system should be assessed and the guidance in paragraphs 5.4 and 5.5 should be followed. Emission factors and primary energy factors should be determined by a qualified person, based on the details of the system and taking account of the annual average performance of the whole system, including distribution circuits and all the heat generating plant, combined heat and power, waste heat recovery, heat dumping, and evidence of future changes to the heat source, for example, replacing or adding new heat generating equipment. Minimising energy used by pumps 6.22 New district heat networks or community heating systems should meet both of the following. a. The design temperature difference for the community heating primary circuit should be a minimum of 20°C. Heat pump-led community heating systems may, however, need to run at a lower temperature difference. b. Variable volume control systems should be used to reduce the volume of water and the pressure difference required from the pumps under part load. Controls 6.23 For wet heating systems, the maximum design flow rate into the dwelling’s heating system should be limited by suitable control and balancing valves to maintain the overall balance in the network and to avoid excessive pumping energy. 6.24 For new district heat networks or community heating systems, the domestic hot water system should have variable volume controls to maintain low return temperatures in the primary community heating circuit. Metering 6.25 District heat networks and community heating systems should be designed to accommodate heat meter(s) for each dwelling. Micro combined heat and power 6.26 The heating plant emission rate of the micro combined heat and power system (micro-CHP) should be no greater than the emission rate of a regular boiler using the same fuel as the micro-CHP. 6.27 The heating plant emission rate should be calculated using all of the following. a. The method in DEFRA’s Method to Evaluate the Annual Energy Performance of Micro- cogeneration Heating Systems in Dwellings. b. The performance data for the micro-CHP packaged according to BSI PAS 67. c. A plant size ratio that uses the nominal heat output of the heating plant divided by the average heat loss of the building when there is a temperature difference of 24.2°C. Building Regulations 2010 Approved Document L Volume 1, 2021 edition 45 O N L I N E V E R S I O N