A new report from Triton Showers has claimed the Future Homes Standard compliance framework could miss an opportunity to further reduce household energy consumption, water use and running costs if domestic hot water demand-reduction technologies are not properly recognised.
The report, Recognising Domestic Hot Water Demand-Reduction in SAP 10.3, explores how the SAP 10.3 methodology treats DHW, which is expected to represent a significantly larger proportion of regulated household energy use as space heating demand falls in highly efficient, low-heat-loss homes constructed under the Future Homes Standard. It is claimed that the current SAP 10.3 approach appears to place greater emphasis on central heating system efficiency, fabric performance and photovoltaic (PV) provision than on reducing DHW demand at source.
Showering remains one of the most significant uses of DHW, making it an important area for improving efficiency and reducing consumption. The report examines the benefits of specifying the latest shower demand-reduction technologies, including high-efficiency instantaneous electric showers and waste water heat recovery systems (WWHRS):
Based on standard SAP assumptions and two daily showers, it is estimated that choosing an instantaneous electric shower paired with a WWHRS could reduce annual shower-related energy use by 35.1%, potable water consumption by 41.6%, carbon emissions by 36.7%. Annual combined energy and water costs, meanwhile, would drop by £137 compared with a conventional mixer shower supplied by a heat pump and hot water cylinder.
Paul Ravnbo-West, market development manager at Triton Showers, comments: “The Future Homes Standard is a welcome and necessary step forward in the transition to low-carbon homes. While it will play a crucial role in reducing space-heating demand, there must also be a plan for the next major source of regulated household energy use: domestic hot water.
“The framework should do more to encourage homes to reduce hot water demand, but the proposed compliance methodology does not currently provide sufficient recognition of technologies that reduce demand at source.”
Triton argues that instantaneous electric showers paired with WWHRS could be particularly relevant in hard-to-treat properties and smaller homes, including apartments, where space constraints, layout limitations or cost considerations can make the specification of a heat pump and hot water cylinder more challenging.
Recommendations include introducing a dedicated domestic hot water demand-reduction metric so that compliance rewards homes for requiring less hot water, as well as closer alignment between SAP 10.3, HEM and Part G to recognise the combined water, energy, cost and carbon benefits of demand-reduction technologies. The report notes that SAP 10.3 currently excludes the costs and operational emissions associated with mains water supply and wastewater treatment.
Paul adds: “Point-of-use demand-reduction technologies like high-efficiency electric showers paired with WWHRS are exactly the type of practical, scalable innovation that should be encouraged under the Future Homes Standard.
“Our recommendations are intended to help policymakers ensure new homes are designed not only to generate heat efficiently, but also to use less hot water in the first place. This approach could help lower household bills, reduce pressure on water resources and provide more flexible compliance pathways for developers, particularly in hard-to-treat properties.”
Download Recognising Domestic Hot Water Demand Reduction in SAP 10.3.
