Verity Close is Kensington and Chelsea’s first low-energy retrofit council home. The objectives were to improve energy efficiency, be gas-free, and complete to a full 21st century specification. Completed in summer 2021, this project has provided a family with a sustainable home that has reduced the heating demand by half and saved an estimated £1,000 in utility bills annually. This project is the basis on which the Council will make the wider Lancaster West Estate carbon-neutral by 2030. Both the internal and external environment work together to reflect one joint sustainable system, in home and garden.
For the UK to meet its carbon reduction targets, a deep retrofit of most existing buildings is required at an estimated cost of £60 billion. It is therefore critical to pilot the most sustainable and cost-effective technologies to reach this goal. At Verity Close, the Lancaster West Neighbourhood Team (LWNT) adopted a ‘whole house’ approach, targeting key areas such as the fabric, thermal envelope, airtightness and improving household services. Initial assessments of the property identified that it had an EPC value of D, a heat loss parameter of 1.31 (c.6.7@50Pa) and a space heating demand of 306 kWh/m2/year. With a current heating bill of around £1,436, reducing the space heating demand was the most critical factor in tackling high bills and the cost-of-living crisis.
LWNT implemented a range of deep retrofit measures that tie into the whole house, fabric first approach. These measures include an MVHR that reduces heat loss through air while ensuring fresh air supply to the property. In addition, this will ensure zero condensation, as well as reducing dust and pollen in the home. An A+++ ASHP supplies all the heating and hot water requirements. 16 Solar Panels have been installed on the roof to decrease electricity use and significantly reduce energy bills. The glass-on-glass modules are A1 fire-rated (i.e. non-combustible), making it the safest option and more energy efficient. A battery system has been installed so electricity can be stored and used at a later date, ensuring they will always have a backup.
To further improve energy efficiency triple glazed windows have been installed to reduce the energy demand by 15kWh/m2 year compared to double glazing - an annual cost saving of around £70 for the resident. Internally, A1 non-combustible Diathonite wall insulation reduces heat lost. Going above and beyond the requirements of a deep retrofit LWNT took the opportunity to improve the garden, creating an eco-friendly space that not only contains an electric car charging point but also a gutterless water butt system, hotbin composter, veg and herbs trugs.
To evaluate performance, the Council conducted thermal imaging, energy performance tests and pre/post EPC’s. The results highlight the roof, west elevation, windows, and doors have a great thermal performance compared to the neighbouring property. Through the implementation of a range of cutting-edge sustainable technologies, the space heating demand was reduced from 306 kWh/m2/year to 81 kWh/m2/year totalling a saving of £926 a year on energy bills. The post-completion EPC rating was B, a significant improvement when compared with similar properties in Verity Close which are typically EPC D. As a pilot project, the learning has meant that the Council would anticipate that identical retrofits would be 15 per cent of the cost of this project, which means it can be replicated at scale.
How is the approach being sustained
Verity Close was designed and implemented as a pilot property, paving the way for sustainable retrofitting across the whole estate. The lessons learned in this process will be applied to other whole house retrofits, in addition to the savings discussed above. When considering the sustainability of the approach it is also important to note some minor annual maintenance costs for the council, these total £352 and relate to the upkeep of measures such as the ASHP, solar panels, MVHR and fire safety related aspects. Furthermore, monitoring equipment and smart technology in the home mean that with time the Council can gather data to see what services are saving the most energy and money for the residents. Moving forward they aim to retrofit the many buildings across the estate with design teams and residents to achieve their carbon neutral goals.
There were a number of lessons learned that will inform the whole estate retrofit of over 800 properties. Some key points that were raised firstly in the design phase, ensure all parties have a full understanding of the building fabric, this can be achieved by being selective on the studies conducted and ensuring all parties have access to the data. Financially, one lesson would be to agree the cost of specialised items in the schedule of works, this will avoid large variations and delays bearing in mind the current supply chain crisis. One final key lesson learnt is to decide on the energy efficiency and retrofit standard from the start. As this was a pilot project a number of processes were trialled.
Going forward, if the property is to be EnerPHit certified, decide this early on as it will impact the decisions and logging process, and if this is to be the standard ensure the Passivhaus model is considered from the start in order to be compliant.