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Approved Document Part L1a – New Dwellings

  • Design Stage SAP to Building Control “No later than the day work starts”
  • Approx 25% reduction in CO2 emissions compared with a 2006 compliant dwelling
  • Maximum average fabric u-values have decreased (eg Walls from 0.35W/m2K to 0.3W/m2K)
  • Carbon emissions for electricity from grid increase by 22.5% (Partly compensated for by a new Emissions Adjustment Factor, which increases the TER)
  • Increased no. air pressure tests. Three per plot type for developments above 6 units (Any dwelling not tested must add 2m3/hm2 to the air leakage rate for a tested plot of same type)
  • Party walls having a cavity must be sealed and insulated or else incur a CO2 penalty
  • Accreditation scheme for cold bridging details to replace the ‘y-value’ in future
  • To exclude Conservatories from CO2 calculations they must be fully thermally separated


Conservation of Fuel and Power in New Dwellings

5 Criteria in the Approved Document Part L1a 2010:

ADL1 Section 4

Criterion 1:

  • Achieving the TER (& definition of DER)
  • Design Standards

Criterion 2:

  • Limits on design flexibility
  • Fabric standards & System efficiencies
  • Domestic Building Services Compliance Guide

Criterion 3:

  • Limiting the effects of solar gains

ADL1 Section 5

Criterion 4: Quality of construction & commissioning

  • Building performance
  • Party walls and other thermal bypasses
  • Thermal bridges
  • Air permeability and pressure testing

ADL1 Section 6

Criterion 5: Providing information

  • Energy Efficient Operation
  • Provision of information on system operation
  • Current spec and further improvements in EPC