Heat Recovery Ventilation

Further reading

• Common Questions about Heat and Energy Recovery Ventilators (124)

Heat Recovery Ventilation

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Technology

The energy consumption of buildings can be lowered by reducing air permeability to 3 m³/h/m² at 50 Pa or less and making structures more air-tight. This concept must be combined with appropriate ventilation, which then enables the recovery of calories otherwise wasted or lost.

A heat recovery ventilator (HRV) is a ventilation system that employs a counter-flow heat exchanger between the inbound and outbound air flow as well as high-efficiency motors. Through a simple mechanical device, energy is reclaimed from exhaust airflows. An HRV can heat or cool incoming fresh air without any additional outside energy source, recapturing 60 to 90% of the energy that would otherwise be lost. To keep the air-tightness of the building intact, all ventilation ducts should be insulated and sealed.

Earth warming tubes (the so-called Canadian well) buried in the soil can be coupled to HRV to act as earth-to-air heat exchangers and pre-heat (or pre-cool) the intake air for the ventilation system.

Future

Heat recovery is an area where substantial cost savings can be made while meeting the necessity to refresh air in the future ‘air-celled’ buildings. There are a number of different HRVs available, and several materials including metal, glass, and plastics have been tested with success.

At present, a counter-current air-air exchanger made of aluminium, copper, or steel is preferred for many situations. It works like a heat pump. Experience demonstrates that heat pumps installed on large systems provide very good results.

Illustration of a current HRV.