project

Investigating the options for low-temperature hot tap water in non-residential buildings

Low-temperature (LT) collective hot tapwater systems have a range of advantages over conventional higher-temperature systems. Legionella safety for hot tap water does represent a significant challenge here. Advantages of LT hot tap water include less heat loss during the distribution/circulation of hot water and the substantially higher efficiency of collective heat pumps by comparison with conventional tapwater systems. In the RELOaDH (‘Reduction of Energy LOss in Distribution and Heating of Hot water’) project, we are looking at whether energy savings can be achieved with low-temperature hot tap water.

Safe hot tap water is a challenge for low-temperature heating systems

Hot tap water should have a temperature of 60°C at the tap (in collective systems), in part because of legionella safety. The same applies to collective tapwater networks. However, a temperature of about 40°C is adequate for showers. In addition, showers consume most hot tap water in homes: in an average home, 72 – 84% of all hot tap water used is for showers. Delivering hot tap water at a lower temperature opens up the possibility of substantial savings and the reduction of peaks in energy use. To keep legionella under control, the use of ‘physical’ technologies (membrane filtration, UV) is possible in collective tap water systems provided the competent authority (i.e. municipality) has granted approval for deviating from the Dutch Building Works Decree for the Living Environment (abbreviated as Bbl, the former ‘Building Decree’). This approval is required for each individual case. In practice, LT hot tap water is still used only rarely, if at all. This is due in part to the complex procedure for obtaining approval for these systems. The standardisation of the technology and the process is key to scaling up renovation concepts with LT hot tap water.

Research into the potential of low-temperature tap water in non-residential construction

The RELOaDH project consists of six work packages / activities that address all the important aspects involved in lowering hot tap water temperatures, viz. water safety, comfort and costs (including environmental costs). In addition to these more substantive areas, there is also a focus on the underlying process of acceptance and implementation.

  1. Literature studies and expert interviews are being conducted to provide an overview of experiences and lessons learned in Europe with LT hot tap water concepts.
  2. Validation of the legionella safety of UF / UV in hot tap water circulation systems. These safety tests are conducted in a controlled lab environment where Legionella Pneumophila is added to the hot water to actually assess the robustness (i.e. the removal or extermination of Legionella Pneumophila) of LT hot tap water systems.
  3. Validation of comfort and hydraulic parameters associated with lower temperatures in practice. When the water temperature is lowered (for a mixing temperature of, for example, 40°C), the hot water flow increases and the cold water flow is reduced. This practical trial looks at the extent to which LT hot tap water is possible without affecting comfort or causing hydraulic problems. This involves collecting and analysing water samples on a regular basis to monitor safety during the practical trial.
  4. When UF and UV are used, there is a shift from energy consumption to material consumption. This work package is developing an assessment framework for the environmental performance of LT tap water systems by comparison with conventional higher-temperature systems.
  5. An overview of standard concepts for LT tap water in existing non-residential buildings. The deliverables from Activities 1 to 4 will be used for this purpose.
  6. Focus group and workshops / webinars. The larger-scale implementation of LT collective systems requires innovation both in concrete areas (system analysis) and in the process (knowledge and support for the competent authorities). Work package 6 contributes to the innovation in the process required to standardise and accelerate the implementation of LT collective systems.

Working on a sustainable future with safe hot tap water

We aim to draw on the activities in the project to arrive at proven safe and functional low-temperature hot tap water concepts for existing buildings. In this way, we are working on a future that will combine sustainability and safety.

The application of physical technologies requires additional management measures to ensure that systems remain safe in the long term as well. The project also covers these management measures. Because individual home-owners lack the requisite knowledge, these types of management measures cannot be adequately guaranteed in the case of individual homes, and this could lead to unacceptable public health risks. That is why this project focuses solely on non-residential buildings (collective systems).