Refurbishing a council block to Passivhaus standards

Refurbing a council block’s energy use to Passivhaus standards was an educational challenge for Steve Groves MCIOB, head of building maintenance at Portsmouth City Council.

Residential block, Wilmcote House, is situated in the most deprived area of Portsmouth and is within the 10% most deprived area of England.

The building was failing: residents were complaining about the excessive costs of the existing electric night storage; maintenance of the building was costly with the windows and roof at the end of their serviceable life; restricted access doors were broken creating ineffective security; decorations were required throughout; and water penetration issues existed within properties and communal areas.

The 11-storey block of flats built in 1968 had an average EPC SAP rating for the properties of 55 (Band D).

We engaged with the University of Southampton, who installed data loggers into a number of properties and the results were compelling: residents weren’t heating their homes to World Health Organisation comfort levels. They were living in fuel poverty as they simply couldn’t afford to heat their homes. 

World’s largest scheme

We conducted a thorough options appraisal before taking the decision to refurbish rather than demolish. We decided to instruct ECD Architects to design a scheme to the ambitious EnerPHiT standard, which is the retrofit equivalent to the Passivhaus standard for new build, and adopt a fabric first approach. The project is the largest residential EnerPHit scheme delivered with residents in occupation in the world.

The extent of the £13M contract included insulating the external envelope with cladding and EWI, replacing the roof, installing triple glazed windows, fitting new hot water cylinders, electric showers and MVHRs, extend the lounge and enclose the communal balconies, decorations throughout and converting the existing office area to four new additional flats.

Principal contractor Engie began work in July 2014, and the project completed in September 2018. 

Implementing the technical requirements was the biggest challenge for the design team and contractor; they had to work together to overcome numerous issues and unforeseen works on site to meet the EnerPHit requirements.

From a client perspective delays resulted in the project being completed later than originally anticipated and we had to manage the residents throughout the extensive works to their homes.

Wilmcote House went from a failing building to a better looking building, improved living environment and extended asset life

However, we have learnt from all the challenges that the project created and it has informed how we undertake resident liaison and consultation on future projects. We have also reflected on how we procure larger projects in future and our role as a client to manage similar refurbishment schemes, particularly the roles of resident liaison and clerk of works that were more effective when we provided the roles directly.  

Best practice study

We have been keen to share best practice and evaluate the project’s success and have continued to engage with the University of Southampton to monitor the building throughout the retrofit process and beyond. We have also linked with the London School of Economics who have studied the social impact of the refurbishment of Wilmcote House on residents.

Preliminary feedback from the universities has indicated that the energy performance of the properties has greatly increased, residents living environment and internal temperatures have improved: residents’ fuel bills have been reduced by 40%.

This is in addition to an aesthetically better looking building, improved living environment and an asset that has had its life extended from a maintenance point of view.