Exergy efficient supply of heat demands in low energy buildings: Balanced ventilation with heat recovery or low temperature district heating?

Due to the low temperature level demanded for space heating and domestic hot water supply in buildings exergy demands for these energy uses are low. However, these demands are often met by high grade energy sources, such as fossil fuels or electricity which could instead be used for other higher-grade applications (e.g. power production). The use of waste heat with low exergy content allows a good matching between the exergy level of the demand and supply sides and represents, thus, a very efficient manner of supplying thermal energy demands in buildings. Similarly, balanced ventilation systems with efficient heat recovery units allow supplying a great part of the space heating demand with low temperature heat recovered from the exhaust air. Here, two different supply options are considered for a small neighborhood: district heating with and without balanced ventilation system with heat recovery. The paper shows the appropriate use of these systems.