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Whole house energy retrofit of six 1970's off-gas bungalow retrofits in Swansea

Swansea bungalows

Our Low Carbon Built Environment (LCBE) team have worked with Swansea Council to retrofit six bungalows located in a rural location. Low carbon solutions have been selected using a whole house retrofit strategy combining reduced energy demand, renewable energy supply and energy storage.

The bungalows are single-storey, L-shaped and terraced. The layout of each two-bedroom home is identical including a living room, kitchen, bathroom and two bedrooms. The homes are off mains gas, and before the retrofit they used oil, LPG or individual electric room heaters as a heating source. Since the retrofit, the homes are all electric.

Low Carbon Solutions

  • Reduce energy demand by installing external wall insulation, loft insulation, replacement windows, LED lights and mechanical ventilation with heat recovery (MVHR).
  • Supply renewable energy using building integrated photovoltaic (BIPV) solar panels on two roof orientations and a ground source heat pump (GSHP) to provide domestic hot water and space heating.
  • Store energy using a lithium-ion battery system.


The comfort of the homes has improved significantly. The temperature is consistent with the thermostat setting by the resident. The humidity levels and supply of fresh air are managed by the MVHR system.

The amount of energy used by the homes reduced by 72% and most of this was provided by the solar panels or the battery. Some excess energy generated by the solar panels was exported to the national grid. This results in both lower energy bills for residents and reduced carbon emissions.

The home’s Energy Performance Certificate (EPC) rating improved from as low as G (12) before the retrofit to A (95-100) after the retrofit.

Lessons learnt

  • Ground source heat pumps with low temperature radiators tend to be more efficient over a year than air source heat pumps. They are very quiet and low maintenance.
  • One lead contractor dealt with re-roofing work and solar panel installation, this is preferable to two separate contractors to ensure responsibility.
  • It is good practice for all installers to meet on site before starting work and to agree a full delivery plan as a team. This encourages contractors to work together and establishes communication channels.
  • Close and regular supervision of the retrofit work is essential to ensure high quality installations.
  • During the planning stage, sharing solutions such as heat pumps and batteries between homes was considered, however, concerns over long term ownership and the need for additional space to locate equipment ruled these options out.

Project team

  • LCBE team at the Welsh School of Architecture, Cardiff University.
  • Swansea Council.
  • Contractors and suppliers who supplied and installed each low carbon technology.