HVAC Tech Tip: Heat Recovery and Ventilation – A True Win/Win

At the Network we’ve seen recent growth in the application of heat and energy recovery ventilators (HRVs and ERVs) as part of commercial building retrofits. Installing either is a great way to improve indoor air quality (IAQ) and lower the cost of providing outdoor air for ventilation.

Ventilation has been a key part of building health for decades. It’s recently been brought to the forefront of the commercial HVAC system discussion because of the COVID-19 pandemic and increased wildfire activity in the region. Proper ventilation involves bringing in ample outdoor air to replenish oxygen and limit or remove moisture, odors, smoke, dust, airborne bacteria, and carbon dioxide. A downside of bringing in outside air is that it needs to be conditioned and that requires energy.

HRVs and ERVs are a great way to ventilate while limiting the associated energy penalty. They do so by exchanging heat between incoming outdoor and outgoing exhaust air streams via a heat exchanger. Heat recovery can be integrated into heating and cooling equipment or come as standalone and bolt on solutions. The latter are typically comprised of a casing, blower motors, a heat exchanger, and controls. We are focusing on these as they’re becoming increasingly prevalent in the market as additions to Ductless Heat Pump (DHP) and Variable Refrigerant Flow (VRF) retrofits. DHP and VRF retrofits can often qualify for utility incentives.

You may be asking yourself; how do I size an HRV? They’re primarily rated based on two factors, airflow and sensible recovery efficiency (SRE). SRE is the measure of how effectively heat is transferred between the outdoor and exhaust air streams and uses a percentage scale. ASHRAE Standard 62.1: Ventilation for Acceptable IAQ is what is most used to determine appropriate outdoor air volume. Section 6: Ventilation Procedure details how to calculate air volumes for both specific zones and an entire system. Overviews of the processes can be found at the following links: Zone Calculations and System Calculations  (courtesy of Trane). Additionally, many manufacturers have their own calculators and can help with sizing if needed.

Older rural buildings were often designed simply to maintain thermal comfort and therefore relied on infiltration to provide outdoor air. Nearly all commercial buildings make good candidates but one building type where we’ve seen these units successfully installed is schools. Follow this link to find a case study highlighting a recent school project done within Network territory (Courtesy of NEEA and Better Bricks). As you’re quoting those aging systems for replacement suggest including an HRV or ERV and tell your customers about the benefits. HRVs present a great opportunity to upgrade your customer’s buildings, indoor air quality, and occupant comfort!

If you have questions don’t hesitate to reach out to us here at Trade Ally Network NW via our website or through your regional field specialist. Keep a look out this Fall for our new HRV incentive!