Controlled Ventilation Systems – An Amazing Machine

In typical construction, our building shell is so leaky that we do not need mechanical ventilation. Instead, we breathe air that comes through all the leaks and cracks in the building envelope, and believe us, there are a lot of them! So yes, we breathe air that comes through our walls, roofs, foundations, windows and doors, and whatever else is found in those places. Dust, pollen, chemicals from materials, mouse pop, bird pop… you get the picture. Not your ideal source for your fresh, breathable air.

Thank goodness for ERV & HRV systems!

(ERV: Energy Recovery Ventilator & HRV: Heat Recovery Ventilator)

Image 1: Schematic image of a HRV unit (

Image 1 displays a schematic drawing of a typical HRV unit. In position 1 outlined in the drawing, fresh air is brought into the unit from the exterior. In position 2 the stale air from your building is exhausted. And wait for it, the magic happens in position 3, the exchange of heat energy. The heat from the exhaust air is given to the fresh air coming into the building. The air volumes never physically mix, but instead flow through a heat exchanger to transfer the heat energy. Up to 90% heat recovery is possible!

The only difference with an ERV unit is that it also transfers latent energy – also know as moisture. This can be very helpful depending on your climate, or your building type. Wintertime can often result in dry interior conditions because of low moisture contents in the exterior air. Cold dry air comes into our buildings, cooling and drying out the interior air. That does not sound very comfortable. By using an ERV system, fresh air is brought into the building and is preheated and given moisture from the exhaust air. During the summertime, the opposite is true. The fresh air is hot and moist, so the exhaust air from the interior space takes some of the heat and moisture out of the fresh air. In essence, the ERV is pre-cooling and offering some dehumidification. This reduces energy loads on our cooling system.

The ERV does everything we need!

  • Filters the fresh air
  • Preheats
  • Pre-cools
  • Humidifies
  • Dehumidifies
  • Exhausts stale interior air, brings in fresh air, without losing all the energy!

High performance buildings demand a lot from the ERV/HRV system. Without the ERV & HRV system in our buildings, airtight, high performance envelopes are not feasible. We need to breathe, and we need to breathe fresh clean air. Now we have the systems that allow us to recapture all the energy in our exhaust air – a truly amazing machine.