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Part L1A Building regulations update...

If you are an architect or housing developer you may be aware the Department for Levelling Up, Housing, and Communities (DLUHC) plan to introduce new Part L building regulation standards. We have highlight the key points below that may be of interest:

Planned introduction: June 2022

Transitional arrangements:

Building / initial notice or deposition of plans need to be submitted before June 2022. And commence work on each individual building by June 2023. Anything submitted after June 2022 has to be built to the new regs. If plans are submitted but building does not commence until after June 2023, un-commenced buildings must be built to the new regs.

Three Performance metrics:

1) Carbon Emissions – DER/TER with 31% uplift from current regs

2) Fabric Energy Efficiency – DFEE/TFEE, level of uplift TBC.

3) Primary Energy - New metric being introduced.

Notional building Specification:

The notional building is what the actual dwelling is compared against – it defines the target values for each of the metrics above. The notional building has the same geometry as the actual building, but has a notional specification set for the building regulations. The planned specification for the notional building is as follows:

External walls: 0.18 w/m2k

Party Walls: 0 w/m2k

Floors: 0.13 w/m2k

Roofs: 0.11 w/m2k

Doors: 1.0 w/m2k

Windows: 1.2 w/m2k,

Air Permeability: 5 m3/m2/hr @ 50Pa

Thermal Bridging: y-0.05 w/m2k/Psivalues from App. R of SAP 10(unchanged from Part L 2013)

Space + Water Heating: Mains gas boiler (system/combi as per actual), 89.5% (SEDBUK), radiators, flow temp 55°C

Controls Single storey, where living area > 70% of floor area: Prog. Stat and TRVs

Controls for all other: Time and Temp. zone control

All: Interlock, ErP Class V Compensator

WWHRS: Instantaneous WWHRS, connected to all showers

Lighting: Capacity:185 X Floor Area, Efficacy: 80 lm/W

Ventilation: Natural with intermittent fans (System 1)

PV Houses: kWp= 40% of largest storey floor area / 6.5

PV Flats: kWp= 40% of largest storey area / (6.5*no. of storeys in block)

Other points to note:

  • SAP assessors will no longer be able to use ACDs for thermal bridging – Psi values will need to be provided.

  • Air tightness testing: No longer allowed to use the sampling +2 rule on a site. Each property needs to be tested.

  • Proposal to have photographic evidence of each element of the construction and services to be supplied to the SAP assessor and Building Control.


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