3/7/2014

What is Heat Recovery Ventilation?

Heat Recovery Ventilation (HRV) is a balanced mechanical ventilation system designed to bring in continuous fresh filtered air from the outside while retaining most of the comfortable room temperature. When in a leaky building, HVAC equipment is constantly heating or cooling the unfiltered, unconditioned incoming air depending on the season. The unconditioned, uncontrolled air can produce drafts and variations in temperature from room to room.

Controlled mechanical heat recovery ventilation greatly reduces unconditioned infiltration from the outside and temperature variations between rooms for added comfort. Well-insulated buildings receive a freshly filtered airflow without the need to open windows. Likewise, the temperature is regulated while minimizing the high costs of constant air conditioning or heating.

How Heat Recovery Ventilation Works

Heat recovery ventilation works by constantly removing stale, moist air from a building’s wet rooms. These rooms typically include bathrooms, kitchens, and utility rooms in homes. While this occurs, filtered, fresh air is delivered to habitable rooms, such as living rooms, bedrooms, and dining rooms.

Heat Exchanger

A unique aspect of a heat recovery ventilator is the heat exchanger. A heat exchanger uses energy from the outgoing stale air, which is used to temper the incoming fresh, filtered air. As a result, the building receives energy-efficient climate control without the expense of high heating and cooling use. Some heat recovery ventilation systems are so efficient that up to 90 percent of the energy from the stale air is recovered and used to temper the incoming air from the outside.

Leaky Home Vs. Energy-efficient Home with High-efficiency Heat Exchanger

As an example, in a leaky home, during a cold 30 degrees winter day, incoming air comes in the building through cracks and opening at an outside temperature of 30 degrees.  The air mixes with the 70-degree room temperature causing drafts and temperature variation throughout the building depending on where the leaks/infiltration is in the building.

With a high-efficiency heat exchanger in an energy-efficient building, the fresh filtered incoming outdoor air is tempered through the heat exchanger and mechanically ventilated evenly throughout the house at 65+ degrees.  The heat recovery ventilator saves energy by reducing cooling and heating needs while at the same time increasing indoor comfort.

HRV Indoor Air Quality Benefits

The primary benefit of heat recovery ventilation is the freshly filtered ventilation it provides to a well-insulated, high-performance building. As construction has developed over time, homes, offices, and other buildings have been built to be increasingly airtight and better insulated.   While today’s airtight buildings improve heating and cooling efficiency more than their less-insulated ancestors, they sometimes create IAQ issues without proper ventilation.

IAQ Benefits of Heat Recovery Ventilation May Include:

  • Decrease airborne contaminants and pollutants, such as dust, mold, and pollen
  • Potential increase in management of asthma and similar conditions, as the air is continuously filtered
  • Decrease or elimination of building odors which may be caused by stale or excessively humid air