Whole house retrofits offer realistic alternative to demolition

A whole-house energy retrofit of six terraced bungalows in Swansea has hiked Energy Performance Certificate ratings (EPC) from G to A and cut average annual energy consumption by two thirds compared to the UK average.

Carried out by Swansea Council and the Welsh School of Architecture at Cardiff University, the project formed part of the £37.3 million SPECIFIC 2 Low Carbon Built Environment project. Enabled by the Welsh European Funding Office, it has won the Collaboration, Domestic and overall Building Champion categories at the CIBSE Building Performance Awards 2023.

The retrofits focused on six properties considered representative of Welsh home types. All were off the mains gas grid, using oil or LPG for heating and hot water, and were considered energy inefficient and expensive to heat, with damp and mould problems and very low SAP ratings.

A key objective was to reduce energy demand and maximise renewable supply, alongside installing efficient and replicable solutions to move towards zero carbon targets.

Energy efficiency measures included external wall insulation, double glazed windows with reduced glazing area, loft insulation, ground source heat pumps, building-integrated solar photovoltaic panels, battery storage and a mechanical ventilation with heat recovery (MVHR) system.

The MVHR system was considered essential for its provision of constant fresh air without the need to open windows and cause heat loss in colder periods. Minimising the loss of space was a concern, so  all technologies are in storage rooms or in non-functional locations, such as ductwork in the ceiling void.

A significant challenge was to complete the works with occupants still at home. To minimise disruption to older residents, the project took place over two phases, with fabric improvements carried out in summer 2018 and supply and storage technologies installed the following winter.

Various measures were implemented to ensure the buildings achieved the intended performance. Detailed specifications were prepared to align installed technologies with legal and technical requirements and to ensure high quality and craftsmanship. The handover strategy included a detailed and user-friendly guide in which all interventions were clearly described and frequently asked questions answered. Swansea Council’s energy manager explained the technologies installed and how to use them.

Pre and post-retrofit measurements of energy performance, undertaken by the Welsh School of Architecture, found big reductions in operational energy consumption and carbon emissions.

EPC ratings improved from G to A, and Standard Assessment Procedure (SAP) ratings increased from 12 to 95.

For the six months outside the central heating season, 95% of energy used for electricity, heating and hot water is provided by the PV panels and batteries, cutting average bills to £3 per month, excluding standing charges.

Average annual energy consumption was 5MWh per home, compared to the UK average of 15MWh, with less than half of consumption (2.2MWh) coming from the National Grid. During summer, 2MWh of excess electricity is generated, which could be sold back to the grid with an appropriate energy supplier. All annual figures were validated by two years of monitoring.

The project team was particularly impressed by the impact of the revitalised home environments on residents’ health and wellbeing. Internal temperatures and humidity were recorded as comfortable and remained consistent throughout the day and night. One resident confirmed that the condition of their asthma improved after the retrofit.

Commenting on the project at the CIBSE awards, one judge called it an ‘exemplar’ demonstrating ‘true collaboration with multiple stakeholders on a challenging retrofit’. The judge went on to say that the team responded to ‘the individual needs of each home and their residents’ and the learnings from the project ‘will have a far reaching impact to the retrofitting of homes in Wales and beyond’.