


Realisation of Zero Energy Buildings (ZEB) for residential use cannot succeed without: minimising leakages, increasing thermal insulation and using reliable and energy efficient system solutions. However, very airtight houses may have a negative impact on thermal comfort and indoor air quality. Focussing on ventilation systems then becomes a requirement.

In cold climates, temperature differences between indoor and outdoor air often exceed 40 °C during winter. State-of-the-art heat recovery systems may not be able to handle these differences while providing proper air quality and preventing excessively dry indoor air.

The present study of energy recovery systems focuses on apartment buildings located in cold climates countries using central air handling units. Heat exchangers recovering sensible heat are compared with energy exchangers with recovery of both sensible and latent heat. For the latter, both adjacent and non-adjacent solutions are considered.

A specific net energy savings factor is developed taking into account the energy recovered, but also the pressure drops and the variation on the effectiveness of the fan given the installation of the heat/energy recovery.

Heat exchangers are efficient and reliable. Recuperative heat exchangers normally imply no air quality problems, but have severe freezing problems. Regenerative heat exchangers encounter small freezing problems, but do not prevent transfer of odours from extract air to supply air. Regenerative energy exchangers provide an efficient heat and moisture exchange between exhaust and supply air flows, diminishing ice formation and the humidification requirement for indoor air.

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