Guide to Part L1a 2010 criteria

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