Legionella protection and energy efficiency for installations and supply

Domestic hot water constitutes an increasing proportion of energy consumption and climate footprint regarding buildings, i.a. because Legionella requires a higher temperature than is needed in terms of
comfort. At the same time, Legionella has become a growing challenge with several cases of illness and a number of deaths as a result of legionnaire’s disease. Denmark has a relatively high incidence ratio but also other countries are challenged. In the project, a major investigation was carried out, as well as the development and demonstration of three measures for protection against Legionella.
The investigation included study on the spread, growth, and reduction of Legionella in domestic hot water systems as well as of authority requirements, standards, and research studies. This showed that due to
biofilm the temperature requirements for treatment against Legionella are underestimated, just as the Danish temperature requirements are on the low end.
A risk assessment tool has been developed based on a recognized method and through adaptation of the found influence parameters with a view to making it usable in practice. The tool will contribute to a better clarification of both existing and new domestic water installations.
An electric booster unit ensures temperature monitoring and optimal control of the domestic water installation based on knowledge of Legionella growth and reduction. The solution will be able to support future adaptation and development of products for the temperature challenge for protection against Legionella.
Use of the relatively environmentally friendly hypochlorous acid allows for lower water temperatures according to those required for comfort. The project has showed that it is possible to bring high Legionella germ
counts down to a tolerable level, which combined with the possibilities in relation to reducing energy and climate footprint makes it relevant to include it in the Danish building regulations.