The Warm Homes Plan has arrived to replace the Energy Company Obligation (ECO). It represents a shift in focus away from a fabric first approach to instead prioritise high-tech solutions such as PV, battery storage and heat pumps.
This change in emphasis raises an important question: is abandoning the long-established principle that improving the building fabric is the best way to deliver energy-efficient homes with improved thermal comfort and indoor air quality as well as low running costs really the right course of action?
In this piece, we take a look at the Warm Homes Plan proposals alongside the established benefits of adopting a fabric first methodology.
Is addressing the building fabric first a fundamentally good idea for energy efficiency?
The fabric first strategy is founded on sound principles. Improving the thermal performance of the building fabric, including the walls, floor, roof, windows and doors, enhances the overall energy efficiency of a home by:
- Reducing the rate of heat loss through the building envelope by using insulation effectively
- Carefully detailing junctions to minimise thermal bridging and associated heat loss
- Reducing gaps in the building fabric to improve airtightness and prevent draughts and unwanted heat leakage
Whenever the fabric is enhanced, it is important that an adequate ventilation strategy is also in place to remove stale air and moisture vapour to maintain good indoor air quality.
The fabric first measures reduce the demand placed on the heating system. As a result, it has to work less and consume less energy.
What part does building fabric play in the Warm Homes Plan?
The £15bn government Warm Homes plan is designed to cut bills, tackle fuel poverty, create jobs and deliver energy security.
Energy efficiency is very hard to achieve without paying attention to the thermal performance of the building fabric. This is supported in the Warm Homes Plan document, where it states that, “Fabric insulation measures, when installed with appropriate ventilation, remain a cornerstone of energy efficiency”.
Due to issues with the quality of solid wall insulation in the ECO scheme, there appears to be a reluctance to continue to support this under the Warm Homes Plan and cavity wall insulation barely gets a mention in the document.
This seems strange as according to the Energy Saving Trust around 33% of heat can be lost through the walls of uninsulated homes.
What are the challenges faced when applying the fabric first approach to existing buildings?
The warm homes plan, ECO, is aimed at existing buildings. Existing homes can present challenges when it comes to upgrading the thermal performance of the building fabric:
- It can be difficult to know exactly what has been built with regards to the composition and construction of an existing home
- Houses may have been subject to home improvement such as loft conversions or extensions that can change the thermal dynamics and ventilation of the original home design
- The quality of the work can be variable, and a record of plans and materials used may not be available
- Measures such as thermal bridging can be harder to address as access may be limited and the exact existing design of existing junction details may be unclear
It is important to carry out a thorough survey of an existing home in order to be able to evaluate and plan the most appropriate energy efficiency measures taking a whole-house approach. This has been addressed by using a Publicly Available Standard 2035 (PAS 2035).
Why is PAS 2035 with its fabric first approach used as a standard for retrofit under government schemes?
PAS 2035 was developed to detail the best way to conduct a retrofit designed to improve energy performance of existing buildings. It includes the requirements to carry out a thorough survey of the existing property. This allows the creation of a risk assessment to determine the project’s complexity and decide upon the design and installation of the most appropriate energy efficiency measures.
By addressing the property in this way, the enhanced thermal efficiency of the building fabric reduces the heating demands on any subsequent high-tech additions such as heat pumps.
What benefits can a fabric first bring that a technology-led approach cannot?
Upgrading the fabric first can:
- Increase homeowner’s thermal comfort by reducing draughts
- Reduce the chances of condensation forming that can lead to mould growth
- Help to limit the effects of overheating by use of insulation materials such STEICO’s wood fibre boards
A technology led approach where PV, batteries and a heat pump is installed will give homeowners the benefits of access to cheap electricity and help to reduce carbon emissions. It may not be able to match the benefits that addressing the fabric first can bring.
Both approaches bring different benefits – together they can work in harmony to deliver high-tech homes that support thermal comfort, low energy use and lower energy bills.