Energy Recovery Ventilators: A Multi-Tasking HVAC System That Solves C-Store Challenges

Energy recovery ventilators (ERVs) are ideal for convenience stores (c-stores). Their benefits extend far beyond utility savings. Major c-store chains have discovered new ways that ERVs—like RenewAire’s HE Series—can reduce capital investments, cut operating costs (OpEx,) and increase sales.

Key benefits include:

• lessen wear-and-tear on HVAC rooftop units (RTU);
• cut construction material/labor costs on bathroom ventilation, electrical wiring and RTUs;
• reduce foodservice, vehicle emission and other odorous airborne volatile organic compounds (VOC) that degrade indoor air quality (IAQ);
• and create a comfortable indoor environment where customers will dwell longer and make more purchases.

An ERV’s primary function is to recover otherwise-wasted energy and precondition incoming outdoor air. In wintertime operation, the cold, dry outside air is preheated and humidified by the outgoing warm interior air. Conversely, in the summertime, the warm incoming air is pre-cooled and dehumidified by the cool, exhaust air.

The foundation of the energy transfer process is the static plate, cross-flow enthalpy core. By physically separating the incoming and exhausting airstreams, the core eliminates cross-contamination during the thermal energy exchange. This ensures continuous energy transfer to incoming fresh ventilation without an energy penalty or overworking the HVAC system.

ERVs, Sensory Marketing, and Dwell Times

Beyond energy savings, ERVs unlock key benefits for c-stores. They create an ideal indoor environment that drives sales. Path intelligence studies reveal that longer customer dwell times inside retail stores are directly correlated with increased revenue. Capturing dwell time offers huge revenue potential. Retail consultant Acosta Group notes 92% of c-store gasoline customers enter for food or beverages. Installing an ERV ensures the clean, fresh indoor air quality that encourages these high-margin shoppers to linger and browse.

Research shows that a 1% increase in customer dwell time yields a 1.3% lift in sales. When a shopper considers a product for 10 seconds instead of the industry average of 5 seconds, the likelihood of buying that product increases by 130%. In other words, more browsing time equates to greater product discovery and higher impulse purchases.

Sensory marketing is a prime example of how ERVs deliver value beyond energy savings. Specifically, using outdoor air dilution to eliminate common c-store odors creates an environment that naturally fosters longer dwell times. Everyday odors—from restrooms, chemical storage closets, tobacco products, foodservice prep areas, and waste receptacles—swiftly degrade IAQ. Combined with potential mold, mildew, or vehicle exhaust infiltration, these poor conditions subconsciously prompt patrons to cut their visits short and leave prematurely.

Because ERVs are energy efficient, c-stores can easily exceed the 7.5 CFM/person code minimum and optimize indoor air quality. Depending on sizing, systems like the HE Series can supply up to 100% outdoor air when needed. For example, the American Society of Heating, Refrigerating and Air-Conditioning Engineers’ (ASHRAE) recommended using 100% outdoor air during the peak of the 2020 COVID-19 pandemic. Consequently, more outdoor air can translate to overall store hygiene.

Supplanting Bathroom Fans for Cost and IAQ

A current c-store ventilation trend is replacing bathroom fans with ERVs. Modern ventilation designs use ERVs to pull out bathroom air, recover its energy, and precondition fresh incoming air. The resulting negative bathroom pressure draws in conditioned sales floor air through bathroom door crevices. Consequently, the design eliminates the capital expense for bathroom fans and conventional supply/exhaust air ducts because the ERV replaces them. Eliminating two bathroom fans and their required wiring/installation by licensed electricians adds up to construction cost savings. Furthermore, maintaining fewer fans reduces overall OpEx.

The HE Series ERV operates with efficient electronically-commutated (EC) motor fan power. Replacing small bathroom fans with an ERV yields significant energy and cost savings over the store’s lifespan. Furthermore, bathroom light/fan integrations are subject to being switched off, which causes odor build up and sensory marketing degradation. On the contrary, an ERV guarantees continuous odor removal regardless if the light is switched off.

Reducing Roof Penetrations

Another advantage to supplanting bathroom fans with an ERV is the possibility of eliminating two roof-compromising building envelope penetrations in c-store architectures that use roof penetrations versus exhausting bathroom gas into soffits. Removing roof penetrations reduces leak risks, prevents thermal bridging, and preserves structural warranties. Fewer penetrations also lower long-term maintenance costs and reduce equipment wind uplift risks.

Furthermore, RenewAire offers flat curbs that can potentially integrate the HE Series and any brand of RTU onto the same curb to eliminate separate roof penetrations for both units.

Recovering Energy for Utility Cost Savings

ERVs are engineered to transfer energy between the exhaust air and incoming outdoor air, preconditioning it close to indoor temperature setpoints. All c-store applications including retail, kitchens, and dining fall under the 7.5CFM/person ventilation rate recommended by ASHRAE Standard 62.1.

While standard RTUs can provide this required fresh air, they use raw natural gas or electricity to condition the outdoor air. This creates significant energy costs in summer and winter seasons, regardless of geographical location. In contrast, ERVs use minimal energy to condition the outdoor air to near indoor temperature setpoints.

Humidity Management and Food Quality

Beyond temperature control, ERVs can also play a critical role in managing a c-store’s humidity. In summertime operation, ERVs can reduce humidity by up to 50% versus untreated air. Additionally, ERVs can lower the latent load on the HVAC system and lessen wear-and-tear over its lifespan. In wintertime operation, ERVs recover humidity from the c-store and put it back into the drier outdoor air for more air comfort.

Proper moisture management yields commercial benefits that extend far beyond simple occupant comfort. For instance, baked goods have a longer shelf life under controlled humidity environments. Improved humidity control also reduces condensation buildups on refrigerated case glass doors. Customers will buy more refrigerated products when they can clearly see them without having to open a series of fogged glass doors. Travel plazas with showers and laundries need strict humidity control to prevent slippery floors and mold growth.

Payback, Long-Term Reliability, and Maintenance

Depending on climate, an ERV in a standard-sized c-store delivers a measurable payback of less than three years. What is even more impactful—though harder to quantify—is the revenue lift from longer customer dwell times, alongside boosted employee productivity and cognitive function driven by pristine IAQ. Since an HE Series ERV’s only moving part is an easily replaceable EC motor, it can deliver an indefinite number of years in energy savings because the enthalpy cores don’t wear out. An HE Series ERV will easily outlive the 15 to 20-year lifespan of the RTU it accompanies.

Besides harvesting heat from bathrooms and mechanical refrigeration rooms, the cooking area is another source for ERV heat recovery. Integrating barometric sensors allows the ventilation design to safely draw residual waste heat back to the ERV without creating air turbulence. This precise balance ensures maximum energy recovery while protecting the exhaust hood’s capture velocity, preventing cooking odors from escaping into the retail space.

ERVs can also help meet stringent ASHRAE 90.1 energy-efficiency targets. Plus, ERVs strengthen a brand’s public commitment to sustainability, energy efficiency, and decarbonization goals.

According to the U.S. Department of Energy’s Better Building Challenge, ERVs can cut building energy use by 10 to 30%. The program encourages businesses to improve their building’s energy efficiency by at least 20% over 10 years.

Enthalpy core-based ERVs, such as the HE Series, require little maintenance other than enthalpy core surface vacuuming and air filter changeouts. The vacuuming and filter replacements can be easily performed by corporate maintenance techs or outsourced contractors during periodic HVAC check-up schedules.

Saving HVAC Equipment Costs

By reducing heating and cooling loads, ERVs allow RTUs to be downsized by up to 30% without sacrificing code compliance. For optimal c-store design, the ERV should be selected first, allowing the RTU to be downsized to match the ERV’s load-reducing capacity. Since ERVs have minimal mechanical parts compared to other enthalpy technologies, their reliability guarantees the working ERV/RTU combination will always have the capacity for maintaining store air comfort.

While VFD options on RTUs increase initial capital equipment expenditures, these upgrades are unnecessary with an HE Series ERV. Equipped with variable-speed EC motors, the HE Series delivers the exact volume of required outdoor air. And, the HE Series can be used to automatically dial in a slight positive pressure in the store. A smaller ratio between supply and exhaust air boosts energy efficiency. It also prevents negative pressure that pulls vehicle emissions and outdoor pollutants through the entrance doors.

How to Integrate ERVs in Future HVAC Designs

Another HE Series ERV advantage is its flexibility to be set up simply, or more complex to save the most energy possible. A simple on/off switch can operate it. For maximum efficiency, open-architecture HE Series controls integrate directly into any RTU or Building Management System (BMS). More sophisticated setups can make the best use out of economizer days, operate in variable speeds dictated by ambient conditions, and use EC motors to dial in the greatest efficiency.

The ERV is an HVAC product with a quick payback that can help c-stores save energy, reduce store odors, improve indoor air comfort/IAQ, and cut construction materials/labor costs.

Increasing sales and cutting OpEx with ERV equipment that feature low maintenance and a two-year payback should interest every c-store HVAC specifying engineer and administrator.