Milton Keynes Council - Lakes Estate regeneration phase 2 monitoring

Milton Keynes Council wanted to develop a greater understanding of the energy performance of their retrofitted homes, so we were appointed to undertake a research study to determine energy and carbon savings, resulting from a set of retrofit energy measures that had been installed.

The Milton Keynes Council phase 2 planned development retrofit programme included the installation of energy-saving measures across 381 properties. We undertook a pre and post-retrofit monitoring study on a sample of eight representative properties, which included the upgrade of:

  • Cladding.
  • Flat roofing.
  • Roof lights.
  • Loft insulation.
  • Boilers and heating systems.
  • uPVC windows.
  • uPVC external doors.
  • Additional ‘minor’ works including asbestos removal and sealing air leakages/draughts.

Services and key activities we provided

The project aimed to provide a business case justification for retrofit, and address quality and comfort concerns around retrofit.

To achieve this we:

  • Measured energy consumption (electricity and gas) and environmental parameters (internal and external temperatures, internal relative humidity levels and carbon dioxide concentrations) both before and after the refurbishment works.
  • Tested building fabric performance (wall and roof U-values, and air permeability) pre and post-retrofit.
  • Conducted a Standard Assessment Procedure (SAP) evaluation based on ‘as measured’ and SAP default values.
  • Undertook a ‘before and after’ Building Occupancy Survey to better understand how tenants typically used energy within the houses.

Lakes Estate SAP improvement graph

Our findings

  • SAP energy efficiency rating improved by 19% and the environmental impact by 25% (on average).
  • Average (excluding B1) gas usage reduced by 24%.
  • Average total energy (excluding B1) reduced by 15%.
  • Post-retrofit electricity was between the average and lower than minimum NEED figures.
  • Post-retrofit gas was between the average and lower than minimum NEED figures.
  • Infra-red thermal imaging confirmed that previously installed blown mineral wool was not 100% complete and was only partially successful in reducing heat loss through external walls.
  • Air permeability was found to be better than the current building regulations in six out of eight properties pre-retrofit, and in all properties post-retrofit.
  • Seven properties performed well with regard to internal air quality, as determined by the measurement of carbon dioxide (CO2) concentrations. The exception was a single-storey bungalow (B2) which showed higher CO2 concentrations than ‘typical’.
  • The average ‘as measured’ external wall U-value (from an in-situ U-value test) was found to be worse than the average ‘as calculated’ value (from SAP methodology construction wall types) and provided supporting evidence that cavity wall insulation was not 100% complete.
  • The ‘as measured’ roof average U-value was found to be significantly lower (better) than the ‘as calculated’ and demonstrated that the material used and the works associated with the flat roof replacement were of a high standard.
  • Two properties had significant overheating in their bedrooms post-retrofit, but insufficient data was available for comparison with pre-retrofit conditions.
  • There were no significant changes in relative humidity between pre and post-retrofit.
  • All tenants reported that they felt warmer post-retrofit, and believed they paid less for their energy. 


Related services

Building Performance Evaluation

There is significant and growing evidence that buildings do not perform as anticipated at their project design stage. Variables that affect building energy performance arise from design, construction, handover and operation. The result is that actual energy performance is often significantly different from its predictions. This is often referred to as the ‘performance gap’ and we provide a service that helps tackle this gap.

Energy Surveys & Audits

Our comprehensive energy surveys and audits provide advice on where the main energy management opportunities lie, and identify the need for more detailed investigations, if required. We also assess the feasibility of energy efficiency measures and renewable energy technologies, in order to reduce a building's energy consumption and carbon footprint.


Many ‘low-energy buildings’ are found to use more energy than the designers thought they would. Benchmarking is key to evaluating a building's likely energy costs, and we can provide a service that does this for you.