Domestic wastewater is generally warmer than 20 °C, while wastewater from hot showers can reach as much as 35 °C. Considering the large amounts of water that need to be processed in buildings and how much water can contribute to heating, it makes perfect sense to use this heat source in some way.
One standard approach is heat pumps that use wastewater flowing through large intercepting sewer ducts as a heat source. Passive heat recovery or a heat pump can also be used to process gray water. Even the very first Passive House building in Darmstadt-Kranichstein was built with a cooling tank from which wastewater sends its heat to the rooms.
This paper discusses direct, passive heat recovery from flowing wastewater from showers as a way to reduce hot water demand.
This in-depth article is available exclusively to iPHA members!
Drain water heat recovery offers a number of advantages:
The following points are particularly important:
[AKKP49] Volume 49 “Energy-efficient hot water systems” of the proceedings of the Working Group on Affordable Passive Houses
Overview of all articles on Passipedia about “Heating and DHW”
List of all released conference proceedings of the 18th International Passive House Conference 2014 in Aachen
Conference Proceedings of the 18th International Passive House Conference 2014 in Aachen