Part L Changes

Part L Changes – June 15th 2022

As most of you will be aware, Part L Building Regulations in England are changing this month.  Whilst these changes only apply to England, the other UK nations may follow suit in due course, so keep you eyes and ears open.

The key changes which affect the plumbing and heating industry are around central heating design, replacement boilers, use of inhibitors, systems filters, zoning TRV’s and building air tightness. The below extracts are taken directly from the Part L document.

Its important for us and you to know what these are so we have put together an easy list below.

Airtightness in new dwellings

4.21 c. Internal building services: where services penetrate the air barrier, holes should be as small as possible and should be core drilled to limit damage. The penetrating services should be sealed to the air barrier using proprietary grommets or collars with air-sealing tape or sealant. Where membranes are penetrated, careful detailing should be used to achieve a robust and durable seal at these penetrations.

Airtightness in existing dwellings

4.23 a. When installing pipework or services, taping and sealing around service penetrations.

Sizing heating and hot water systems Sizing space heating systems

5.8 The specification of space heating systems should be based on both of the following.

  1. An appropriate heat loss calculation for the dwelling.
  2. A sizing methodology that takes account of the properties of the dwelling, such as the Chartered Institute of Plumbing and Heating Engineering’s Plumbing Engineering Services Design Guide. Systems should not be significantly oversized.

5.9 Where a gas combination boiler is used, the boiler type should be selected to modulate down to the typical heating load of the dwelling.

5.10 Where a wet heating system is either:

  1. newly installed
  2. fully replaced in an existing building, including the heating appliance, emitters and associated pipework all parts of the system including pipework and emitters should be sized to allow the space heating system to operate effectively and in a manner that meets the heating needs of the dwelling, at a maximum flow temperature of 55°C or lower.

Where it is not feasible to install a space heating system that can operate at this temperature (e.g. where there is insufficient space for larger radiators, or the existing distribution system is provided with higher temperature heat from a low carbon district heat network), the space heating system should be designed to the lowest design temperature possible that will still meet the heating needs of the dwelling.

Controls System controls and zoning

5.14 For wet heating systems in new dwellings with a floor area of 150m2 or greater, a minimum of two independently controlled heating circuits should be provided.

5.15 System controls should be wired so that when there is no demand for space heating or hot water the heating appliance and pump are switched off.

5.16 Domestic hot water circuits that are supplied from a hot water store should have both of the following.

  1. Time control that is independent of space heating circuits.
  2. Electronic temperature control.

5.17 Primary hot water circuits for domestic hot water or heating should have fully pumped circulation where this is compatible with the heat generator.

5.18 Wet heating systems should ensure a minimum flow of water to avoid short-cycling.

5.19 For space heating systems, temperature control should be installed for the heating appliance. Thermostatic room controls

5.20 For heating systems in new dwellings, or when a heat generator such as a boiler is replaced in an existing dwelling, each room should be provided with thermostatic room controls. These should be capable of being used to separately adapt the heating output in each room served by the heating appliance. Where justified in accordance with paragraph 5.20, heating may be controlled for each heating zone rather than individual rooms. NOTE: There is no need to install thermostatic room controls in rooms/zones without heating in new or existing dwellings.

NOTE: Installing thermostatic room controls may not be technically feasible in some cases. These may include the following.

  1. Dwellings with very low heat demand (e.g. less than 10W/m2 ).
  2. Dwelling with buffer zones for heat absorption or dissipation with high thermal mass.

5.21 It may be justified to control a heating zone rather than individual rooms in either of the following cases.

  1. In single-storey open-plan dwellings in which the living area is greater than 70% of the total floor area. In such cases, the dwelling should be considered as a single heating zone.
  2. Where two adjacent rooms have a similar function and heating requirements (e.g. kitchen and utility room). In such cases, the adjacent rooms should be considered as a single heating zone.

NOTE: Exhaust air heat pump systems, which extract heat from the exhaust air of a dwelling, may not need to provide independent thermostatic control to individual rooms. Providing room/ zone control on this type of system is unlikely to be economically and/or technically viable. However, other space heating systems also in use in the same dwelling should be controlled using thermostatic room controls as described above.

NOTE: Commissioning heating systems is covered in Section 8. 5.22 The standards in paragraphs 5.20 and 5.21 may be satisfied by providing any of the following.

  1. Both of the following.
  2. A thermostat in a room that the heating circuit serves.
  3. An individual thermostatic room control for each heat emitter, such as a thermostatic radiator valve, on all heat emitters outside the room that contains the thermostat. Thermostatic radiator valves should not be used in the same room as the thermostat.
  4. An individual room/heating zone thermostat or fan coil thermostat for each room or heating zone.
  5. An individual networked heat emitter control for each emitter.

System specific guidance for commissioning Hot water systems for space and domestic hot water heating

8.8 Before a new heating appliance is installed, all central heating and primary hot water circuits should be thoroughly cleaned and flushed out.

A suitable chemical inhibitor should be added to the primary heating circuit to protect against scale and corrosion. In hard water areas, suitable measures should be taken to treat the feed water to water heaters and the hot water circuit of combination boilers to reduce limescale accumulation.

Domestic central heating systems should be prepared and commissioned to BS 7593.

NOTE: The Benchmark Commissioning Checklist can be used to show that commissioning has been carried out satisfactorily for the heating and hot water system and its heat generation source.

Want to find out more check out the government website.

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