Heat Recovery Ventilators

Heating, ventilation, and air-conditioning systems (also called HVAC), are constantly evolving with humanity.

For instance, until several decades ago, people living in low temperatures had to suffer through cold winters without any relief.

The same applied to ultra-hot summers – accept it was hot! This led to the invention of much-needed heating and cooling systems.

While these were initially welcomed with much fanfare, people soon dreaded the high cost of using these systems.

This in turn led to more energy efficient windows, so people could retain the inherent heat within a house during winter and coolness during summer. In turn, this reduced the load on HVAC systems, leading to more manageable utility bills.

Now, this has caused a new problem, which is the lack of ventilation within a house. When this remains untreated, this can lead to a vicious cycle of moisture retention, mold, etc.

Fortunately, this is easily solved with a clever piece of mechanical equipment, in the form of heat recovery ventilators (HRV).

How does it work?

An HRV is first and foremost a ventilator. For this, the HRV comprises of a mechanical box with 2 tunnels, one to allow stale (exhaust) air to pass outside, and another to bring fresh air into the house.

Do note that these do not mix, and stay separate at all times. Hence, you are assured that the incoming air is indeed fresh.

It also needs to retain the heat/ coolness within the house, as compared to the outside temperature. For this, the HRV also contains a smartly designed heat exchanger core, made from a good thermal conductor material like aluminum.

With this, the core is able to retain the temperature of outgoing air, and transfer this temperature to the incoming air.

For instance, in winter, the outgoing stale air is hot. This heats up the HRV core when it passes out. This hot core is then used to heat the incoming fresh air.

In summer, the outgoing stale air is also much cooler than the incoming fresh air. Again, the HRV’s core is able to retain this temperature, and then used to cool the fresh incoming air.

In both cases, the quality of the fresh incoming air is unaffected. In addition, the temperature is maintained within the house even during exchange of air, hence reducing the load on the HVAC system.

Limitations of HRVs

The HRV will not be useful to reduce utility costs in the following situations.

• Lack of traditional heating/cooling systems. Without this, the difference in temperature between the air inside and outside is insignificant.
• Rooms with open windows. This will override the HRV’s ventilation system, thus neutralizing its ability to retain the temperature inside.

Due to the HRV’s ability to “recover” heat, people sometimes confuse it with traditional heating and cooling systems. But the HRV is neither a heater nor a cooler. It is simply a ventilator with the additional ability to retain the temperature of outgoing air and transfer it to incoming air.