Brent Housing Retrofit Pilot

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Exceeding energy performance certificate targets in Brent

In 2021, we undertook a pilot housing retrofit project for Brent Council, which laid the foundations for the council to develop its wider housing retrofit strategy.

Using a fabric-first approach, the Brent pilot saw the team undertake a deep retrofit of a void property, allowing the council to understand various energy efficiency measures in unoccupied properties, giving valuable insight to inform future retrofit investments while causing no disruption to tenants.

Reducing predicted carbon emissions from 6.8 tonnes to -0.5 tonnes per year, the project exceeded all expectations and took the properties from an Energy Performance Certificate (EPC) F rating to an EPC B rating, exceeding the Government’s targets for housing retrofit.

A collaborative design journey

Designed to form an understanding of retrofitting at scale, Brent Council’s pilot project was commissioned to give the council extensive opportunities to learn and understand the best possible means to achieve its carbon reduction strategy across its housing portfolio.

The project was designed to explore the possibilities of retrofit, enabling the team to understand the various combinations of energy efficiency measures to see what savings could be achieved alongside EPC gains. This journey saw the team overcome shared challenges, including the need for all stakeholders to understand and comply with PAS 2035 standards.

A deep retrofit using a multi-measure approach

Energy modeling was completed by Wates PAS 2035 Compliance Partner, Energy Specifics, with a fabric-first approach to first and foremost reduce heat loss. The project embraced multiple measures to reduce energy consumption. Insulation to the thermal envelope was the primary focus but needed to be designed to accommodate multiple fl ats within one property. Insulation installed included a blend of fire safety compliant Rockwool external wall insulation, new windows, and internal wall insulation as well as insulation to the shared, unheated hallway.

A range of additional energy efficiency measures were modelled and reviewed by the team, including energy-efficient windows, PV panels, and energy-saving heating. The team considered upgrades to condensing boilers, infrared heating panels, high heat retention storage heaters, and air-source heat pumps. High-heat retention heaters were selected as a reliable and trusted technology with an improved insulation to improve efficiency, a solution that was chosen to reduce installation disruption to residents.

Balancing air tightness with ventilation

Although effective, improving the air tightness of properties also requires appropriate ventilation to mitigate the risk of dampness. Decentralised mechanical extract ventilation – an energy-efficient ventilation solution that uses continuously running small fans to extract stale air out of a room – was selected as the most cost-effective means of achieving the desired ventilation while also ensuring compliance with PAS 2035 standards, which mandates permanent mechanical ventilation. This achieved air tightness of 0.46 m3/m2/hr@50pa, bringing the property close to Passivhaus standard while avoiding the costly installation of new mechanical ventilation and heat recovery systems.

Developing best practice

Following completion of the pilot, the team completed a joint ‘lessons learned’ report to inform best practice. At a time when budgets must be balanced with the outcomes of energy efficiency measures, the team found that EPC improvements can be achieved without expensive and intrusive work being undertaken, the benefit of which will also support work to future properties where tenants are in situ.

Though undertaken at a void property, the Brent Council pilot retrofit was carried out alongside an adjacent tenant, whose welfare had to be considered. Our team worked closely with the resident, agreeing to additional decoration works as a gesture of good will. Similarly, the project team identified additional works to overcome damp, mould, structural issues, and general disrepair, all of which were addressed to facilitate the additional weight of the new PV panels. This work was delivered by the Wates team alongside other planned works, ensuring a concurrent and smooth project delivery.

Ensuring cost-effective solution

Throughout the project, the Wates team worked closely with Brent Council to evaluate the cost-effectiveness of all energy efficiency measures with the aim of understanding the wider impacts of decision making for retrofit projects in the future. The result is a scalable project that Wates, Brent Council and all project stakeholders can take forward to inform future housing retrofit, enabling the council to achieve the Government’s ambitious net-zero targets.

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