Driving net zero: Comprehensive evaluation of whole life carbon in domestic hot water systems

Low-temperature domestic hot water (DHW) systems provide significant carbon reduction benefits, supporting the UK’s 2050 net-zero target. Typically, low water volume applications do not need recirculation and storage when instantaneous heaters are employed, such applications can be more flexible in terms of temperature range and safety requirements. However, commercial applications may have high volumes of hot water and hence, will require high working temperatures to satisfy the recirculation requirements. This study developed a comprehensive toolkit to benchmark the embodied and operational carbon in terms of kgCO₂e/m² for various DHW systems, including equipment, refrigerants, and operational emissions. Analysis of seven DHW designs for an office building revealed that low-temperature systems consistently demonstrate the lowest whole-life carbon (WLC), underscoring the impact of grid decarbonisation and low-GWP refrigerants. The WLC results are normalised per square metre of floor area. Low-temperature systems showed the lowest WLC even with the inclusion of water treatment and chemical dosing systems.

Practical Application: Our contribution aligns with modern building industry practices by promoting the adoption of low-temperature domestic hot water (DHW) systems to reduce carbon emissions. This approach supports the industry’s shift towards sustainable construction and the net-zero carbon target by 2050. We emphasise the benefits of these systems, particularly in reducing whole life carbon (WLC) impacts, which is crucial for environmentally conscious building designs. By demonstrating that low-temperature systems maintain low WLC even with additional components like water treatment, our work provides practical insights for professionals aiming to implement energy-efficient and sustainable heating solutions in commercial buildings.