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Increasing airtightness and isolation of residential buildings in today’s climates cause challenging situations for the summer indoor climate. In combination with ventilation for fresh air, it calls for intelligent control of passive cooling when available, and active cooling when needed.
The combination of heat recovery ventilation and an air-to-air heat pump cooling system is a solution to these challenging situations. With the exhaust air heat pump cooling system, heat is transferred from the supply air (which is getting colder) to the exhaust air (which is getting warmer).
Such a ventilation system is monitored throughout the summer for an actual installation in The Netherlands. The control of such a system depending on the actual indoor and outdoor conditions is explained in a control diagram.
Correlation diagrams show how the ventilation supply air temperature and humidity varies with outdoor temperature in accordance with the passive or active cooling mechanism. It has been shown that the sensible cooling can be doubled with active cooling when compared to passive cooling. The total (sensible + latent) cooling of the air-to-air heat pump amounts up to 1100 W with 150 m3/h and up to 1700 W with 270 m3/h.
Limitations of the technology are explained with diagrams for conditions where the condenser gets too hot. For these situations the ventilation air flow rate is first automatically increased to allow the condenser to cool. If necessary, the heat pump is shut off intermittently to prevent damage to the condenser.