Comfort of Domestic Water in Residential Buildings: Flow, Temperature and Energy in Draw-Off Points: Field Study in Two Danish Detached Houses

Anna Marszal-Pomianowska,Michal Pomianowski,Olena Kalyanova Larsen,Sofie Sand Knudsen,Jacob Scharling Jørgensen,Rasmus Lund Jensen

doi:10.3390/en14113314

Abstract

There is very little knowledge on the occupant actual hot water comfort (temperature and flow), usage practice, and routines (temporal and spatial distribution of hot water usage in a household). This paper describes the results from the total and hot water measurements in two Danish detached houses. The results show that, at the draw-off points, the temperature of 55 °C is never asked by the occupants, not even in the kitchen sink. The domestic water temperature differentiates depending on the function of the draw-off point, with the shower and kitchen taps being most energy- and water-intense. They constitute around 90% of the hot water use in the house. Shower units on average demand for highest temperature (i.e., 35.5 °C to 40.4 °C). Hand washing operates, on average, at temperature between 20.5 °C to 26.5 °C. Average water temperature at the taps located in utility room varies between 23 °C to 26 °C. These in-depth insight in the total and hot water use in two new-built low energy houses, can a) help building professionals designing more efficient hot water installations; b) enhance the research work on energy flexibility buildings by providing knowledge on most energy-intensive draw-off points; and c) facilitate district heating professionals in improving the network performance.

Highlights

The energy reduction initiatives were and still are a cornerstone in the transition towards fossil-free energy systems
This paper aims to contribute to the knowledge on real comfort of domestic water by describing results from high resolution domestic hot water (DHW) measurements in two energy-efficient houses located in Denmark
The results showed that the average DHW consumption is 32.2 L/day per person, which is calculated to an energy consumption of 0.83 kWh/day per person

Summary

Introduction

The energy reduction initiatives were and still are a cornerstone in the transition towards fossil-free energy systems. The energy efficiency actions (e.g., tightening the energy frames and/or making stricter the regulations for air tightness and thermal characteristics of building envelope and energy performance of heating, ventilation, and air conditioning) aimed primarily to reduce the energy use for space heating (SH). These measures have been efficient and SH decreased (e.g., in Denmark, the final energy consumption per m2 for heating the dwellings dropped by 25% since 1990 [3])

Methods

Results

Discussion

Conclusion