Passivhaus retrofit social housing: A pilot of two family homes in Norwood

Two social housing properties in Norwood were chosen for a deep retrofit, renovating the almost derelict properties to create two very energy efficient home for families in Lambeth.

The Challenge

Lambeth’s Climate Action Plan (opens in a new window) commits to taking every practical opportunity to reuse and retrofit existing buildings and ensure all new development meets net zero standards. The plan aims to retrofit all of Lambeth’s existing buildings (residential and non-residential) to an average of EPC level C or higher by 2030.

The two void properties on Bloomhall Road offered the unique opportunity to try a fully sustainable renovation using innovative techniques and showcase how we can make our social housing energy efficient and resilient to the impacts of climate change and energy price fluctuations.

24 and 26 Bloomhall Road are two-story brick terraced houses that have been vacant due to significant damage caused by ongoing issues with subsidence. They were chosen to undergo total renovation to meet Passivhaus standards so that the properties would be energy efficient and comfortable while using minimal heating and cooling. The Passivhaus method uses specialist membranes and sealants to ensure the properties are airtight. This approach, paired with air source heat pumps and ventilation systems, reduces heat loss from the property and makes it very energy efficient.

Action Taken

Building contractors Niblock were commissioned to deliver the project as they specialise in refurbishment and renovation projects. Bailey Garner was appointed as the Passivhaus designer and contract administrator, providing ongoing project support.

Before work could begin on energy efficiency, adaptations were needed to make the properties structurally safe. Work included:

• Support beams and drilling to stabilise the property after subsidence
• Chimney breast and asbestos removal
• Temporary works installed to the rear elevation and rebuilding of the existing masonry
• Pitched roof repairs and adaptations
• New floors and rear wall
• New staircase

New support beam and flooring installed to stabilise the property after subsidence.

Why the Passivhaus method? 

To achieve Passivhaus EnerPHit standards, the properties needed to be retrofitted using a ‘fabric first’ approach. This meant upgrading the building fabric (walls, roof, floors, doors, and windows) to create a highly energy efficient dwelling and significantly reduce energy demand. Some EnerPHit retrofits have recorded a reduction in energy demand by up to 93%. 

Both properties have had the following features and facilities implemented:

• A specialist membrane, Passive Purple, was installed to create an airtight barrier throughout the whole property, and thorough air testing was undertaken to significantly reduce heat loss from the properties and create a stable temperature inside them.
• Photovoltaic solar panels to provide alternative, greener energy, reducing the need for national grid electricity and providing energy security.
• External Wall insulation and new triple-glazed windows and doors reduce heat loss and provide a warm, safe environment.
• New internal doors, frames and architraves to improve the fire safety standards.
• Landscaping works in the front and back gardens to make a safe outdoor environment for new tenant families.
• Each property has a new Air Source Heat Pump to generate the heat for the ventilation and hot water.
• Mechanical heat recovery as part of the ventilation system that recovers heat from warm rooms and disperses it into other parts of the home, i.e. from the kitchen to the bedrooms.
• Smart monitoring and controls to make sure excess energy is not used.
• LED lighting throughout the properties.

The Results

The new and improved houses will reduce energy bills, as Passivhaus buildings use 90% less energy than typical buildings. The reduced energy needs and solar panels also mean the houses will produce fewer carbon emissions.

The ventilation system that heats the rooms also extracts stale air and circulates fresh air, improving the air quality, reducing the risk of mould growth and keeping a comfortable temperature throughout the year. These features help improve the health and wellbeing of the residents by providing a warm, comfortable and easy to heat home.

Learnings from Niblock

As the building contractor, Niblock had to work to a very limited specification to achieve the Passivhaus status, which was a challenge with properties that had so many structural issues. Below are their learnings from the scheme

• The market is developing and heavily relies on innovation.
• Detailed surveys at the start of any retrofit project are essential to assess the building's condition, including structural issues.
• Early engagement with the supply chain is crucial. Effective programming and planning were key to managing long lead times for materials.
• A collaborative approach throughout the project contributed to its success.
• The technologies implemented are typically designed for new build applications, so it was important to understand how these details interface with the existing fabric of the building.

Niblock said, “Working on the retrofit of these two properties was a rewarding challenge. We improved their energy efficiency by integrating innovative solutions and collaborating with Lambeth and Baily Garner.”

Learnings from Baily Garner

Baily Garner LLP was the Passivhaus designer and worked closely with Niblock and Lambeth Council to ensure the project met all the necessary certificates and checks. Below are their learnings from the scheme:

• There is a challenge in carrying out retrofit works within the current planning application process.
• Meeting the administrative and design requirements of the Passivhaus certification process requires specialist knowledge.
• Good, regular communication between project team members is paramount for such a complex project.
• The project provided an opportunity to develop knowledge and showcase the ability of BG’s Retrofit Team.
• The project provided an opportunity to support the upskilling of contractors and subcontractors.
• The project provided an opportunity for Lambeth Council to learn practical lessons on installing renewables and consider ways to manage future maintenance.

Baily Garner is proud to have had the opportunity to be part of such a progressive and groundbreaking project.  In collaboration with Lambeth Council and Niblock, we have been able to prove that retrofitting existing properties and reducing energy demand through the Fabric First approach is a viable option in the quest to move towards climate change resilience and Net Zero in housing. Through the use of innovative sustainable technology the project has succeeded in its objective of providing a comfortable living environment and reduced energy costs for residents.

Carbon savings

Compared to doing nothing to the properties, the proposed designs would save 96,431 kg of CO2, an 85% reduction in life cycle CO2 emissions, using average residential energy consumption as a benchmark.