Energy efficiency of exhaust air heat recovery while controlling building air humidity: a case study

Ron Zevenhoven, Rickard Erlund, Tor-Martin Tveit

Research output: Chapter in Book/Conference proceedingConference contributionScientificpeer-review


One modern method of lowering the energy use by buildings is to exchange heat between ventilation air leaving a building and incoming fresh, typically colder air. Moisture in the exhaust air condenses in the heat exchanger, giving liquid water that must be removed. With a low absolute humidity of inlet fresh air especially at low ambient temperatures, a significant overall drying effect results for the air inside the ventilated building. Increasing the air humidity by, for example, spraying water or increasing the watering of plants may give an increased energy penalty. This paper presents the analyses of the energy efficiency of a modern house equipped with external heating supplied by a geothermal heat pump and an exhaust air heat recovery system (EAHR). Indoor temperature is controlled at 22°C and the relative humidity at between 30 and 70%. Temperature and humidity of inlet air and its flow rate into the building are varied and the effect on the power use by the heat supply is assessed. The results show that without moisture recirculation in the EAHR a net water loss up to 1 kg/h from the building may be possible. Also several kWh electricity may be consumed daily by a (geothermal) heat pump that supplies heat to a 99 m2 modern house depending on outdoor temperature and indoor and outdoor air humidity. Besides water consumption, this may imply 10-15 % of total electricity use.

Original languageUndefined/Unknown
Title of host publication5th International Conference : Contemporary Problems of Thermal Engineering, Gliwice, Poland, 18-21 September 2018
EditorsWojciech Stanek, Lucyna Czarnowska, Wojciech Kostowski, Paweł Gładysz
PublisherThe Silesian University of Technology
ISBN (Print)978-83-61506-46-1
Publication statusPublished - 2018
MoE publication typeA4 Article in a conference publication
EventInternational Conference on Contemporary Problems of Thermal Engineering - 5th International Conference on Contemporary Problems of Thermal Engineering (CPOTE 2018)
Duration: 18 Sept 201821 Sept 2018


ConferenceInternational Conference on Contemporary Problems of Thermal Engineering


  • Energy efficiency
  • Zero-energy building
  • air humidity
  • heat recovery

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