Domestic Hot Water Heating in nZEB

Abstract

Domestic hot water (DHW) is needed for personal hygiene and washing. In low-energy and passive buildings, energy consumption for DHW water heating can exceed the amount of energy used for heating the building. DHW systems are included in the energy use assessment of the buildings as one of the so-called EPBD (Energy Performance of Building Directive) systems. Since DHW is needed throughout the year, solar energy or ambient heat can be utilized with high efficiency and with significant impact on the share of renewable energy sources in energy for the operation of the building. The rational use of DHW has a major influence not only on the rational use of energy but also on environment protection. Lower DHW consumption decreases drinkable water use, which is pumped from natural reservoirs or treated in water-cleaning systems and transported to the buildings. Lower DHW consumption reduces the drain of waste water that must be treated in central water cleaning utility systems. Note 1 Despite the fact that water covers 70% of our planet, only 2.5% is not salty. Of this amount, only 0.3% is drinkable (Water in the city, European Environment Agency, 2012). Note 2 In the City of Ljubljana (population: 300,000), overall fresh water consumption is approx. 200 L per inhabitant per day. The majority is used in households (68%), trade and shopping centres (10%), and industry (4%). The water supply system is continuously refurbished to decrease network leakage. Water losses in network were over 100% of the supplied water in 1991; were decreased to ~30% in 2011 (Municipality of Ljubljana, VO-KA, 2017).