Part L 2020: What to Expect and Potential Changes

Mainer Associates expect there to be significant changes to Part L Building Regulations in 2020. This article describes the current issues experienced by the UK’s domestic and non-domestic building stock and the unintended consequences of current legislation. The potential changes to Part L to address these consequences will also be discussed.


The pitfalls of current legislation

Our building energy standards are shaped by the European Union’s 2010 Energy Performance of Buildings Directive and the 2012 Energy Efficiency Directive. It is expected they will still influence UK regulations post-brexit. Several ‘unintended consequences’ from this legislation that are generally experienced in-built assets throughout the UK include:

  • Homes are overheating.
  • A focus on air tightness has led to poor indoor air quality, creating a dependence on mechanical ventilation to address high VOC concentration, airborne moisture and high particulate pollution.
  • Energy performance gaps.



The unintended consequences from past and current building regulations and current Part L have come as a result of:

  • Designing for compliance and not acknowledging how actual operational use of built assets differ from design intentions.
  • Compliance gaps.
  • Lack of management, monitoring and analysis of buildings, post-occupancy.


Part L 2020

It is anticipated Part L of building regulations ‘Conservation of Fuel and Power’ will be amended in 2020. The most significant potential change is a switch from CO2 to primary energy as the metric to assess building performance. This suggests a big step towards a fabric first approach , designing buildings for energy efficiency from the start, instead of designing an asset and then installing renewable and low carbon technology to meet CO2 reduction targets.

Maximising the performance of building fabric before considering electrical and mechanical systems is a great step towards improving sustainability of the built environment.


Potential Changes to Legislation

There are potential changes to the UK building regulations with intention to address key challenges to achieving better performing buildings and the increasing influence of above-regulatory standards.

Potential changes to energy and sustainability standards in the coming years:


  • Re-calibration of fuel factors for new homes.
  • Elemental standards for existing buildings.
  • Limiting efficiencies for fixed building services.
  • Adoption of SAP10 to deliver new minimum standards and accommodate ventilation/overheating changes.
  • A switch from CO2 to a primary energy metric.


  • A ‘fuel neutral’ notional building for new non-domestic buildings.
  • Elemental standards for existing buildings.
  • Limiting efficiencies of fixed building services.
  • SBEM changes to deliver new minimum standards and to accommodate any ventilation and overheating changes.
  • A switch from CO2 to a primary energy metric.

Future regulations on ventilation are likely to provide clarity on Part F guidance and simplifying the approach to calculating ventilation rates. There is also expected to be an review of air tightness testing procedures and the competency of testers along with a review on the way the national calculation method (NCM) credits air tightness.

In regard to overheating, by 2020 the government will have to decided where the requirements to reduce overheating risk should be placed in new legislation. Will this come under Part L or the new AD? It is also expected the method for determining overheating risks for dwellings will be changed in order to help address this issue at design.

Share on Social...Share on FacebookShare on Google+Tweet about this on TwitterShare on LinkedInEmail this to someone