The Wilmcote House development was built at a time when energy performance was less of a priority than it is today. The in-depth refurbishment that took place in 2014 is a great example of how an energy efficiency renovation can make comfortable living affordable for social housing residents. Portsmouth’s 100-home home Wilmcote House was constructed in 1968 using prefabricated concrete panels. Relying on just 25mm of insulation and electric heating, it made it very costly for residents to stay warm indoors. As a result, many residents were unable to afford to heat their homes adequately. This is a serious issue in Europe, where 10.8 percent of the population cannot afford to keep their homes warm. Countries with the most energy poverty have higher winter mortality rates, in both warm and cold climates. In Europe, over 80 million people live in damp homes, which can cause respiratory illnesses.

The challenge

Although the residents of Wilmcote House liked their flats and their location, poor energy performance was a major issue. It led to high heating bills and mould, damp and condensation which can adversely affect health. Recognising that poor insulation was the main problem, the City Council engaged ECD Architects to design and lead a major energy efficiency upgrade aimed at meeting the EnerPHit standard, which is the equivalent of the Passive House low-energy building standard but for renovations. The aim was to reduce heating demand by 90 percent and extend the building’s life by 30 years.

Portsmouth. UK

Project location


Wilmcote House project completed
Wilmcote House project completed

The solution

The £12.9 million retrofit project took place while the residents remained living in their homes. Starting in the summer of 2014 and finishing four years later, the 100 three-bedroom maisonettes, two three-bedroom flats, two one-bedroom flats and seven one-bedroom ground floor flats within Wilmcote’s three connected 11 storey blocks were upgraded to provide comfortable, safe and thermally-efficient homes for residents that will endure for many years to come.

The “deep retrofit” project involved different insulation measures, with ROCKWOOL REDArt® providing external wall insulation, Rockpanel® used for cladding and a selection of our fire protection products included for fire safety. The external insulation was fitted as a 300/400mm zone fixed to newly assembled, external steel frames to insulate and wrap the entire building. The result is excellent thermal performance and exceptional air tightness, reducing draughts, condensation and mould growth.

The result not only helped take residents out of fuel poverty – it also made Wilmcote House a more pleasant place to live and gave the residents a new sense of pride.

Passivhaus and EnerPHit Standard definitions

Passivhaus Standard: Passivhaus buildings provide a high level of thermal comfort using minimal heating and cooling by following strict guidelines. Most of the heat demand is met by passive heaters such as the sun, human heat and heat from home electrical appliances. By definition; “a Passivhaus is a building in which thermal comfort can be achieved solely by post-heating or post-cooling the fresh air flow required for a good indoor air quality, without the need for

additional recirculation of air”.

EnerPHit Standard: EnerPHit is the standard for renovation and retrofit projects wanting to achieve Passivhaus Standard. It has slightly fewer restrictions to allow for the existing architecture which may mean Passivhaus standard is not possible. This is the equivalent of the Passivhaus retrofit standard.

Project Data

Year 2014
Building Type Multi-unit house
Application External
Product type Hardrock (DD) Multi-Fix