Educational institutions, from elementary schools and high schools to sprawling university campuses, are energy-intensive ecosystems. Heating, cooling, and hot water demands drive up operational costs and carbon emissions, often straining underfunded budgets. With dollars stretched as far as possible, schools must find smart, cost-effective ways to reduce expenses while still meeting their energy needs.
One promising solution that offers long-term savings is to adopt waste heat recovery systems that capture and reuse otherwise wasted thermal energy. This approach not only cuts energy bills to free up resources that can be redirected to core educational initiatives but also has the added benefit of reducing greenhouse gas emissions.
In simple terms, air-to-water waste heat recovery takes advantage of basic thermodynamic principles to capture heat that would normally be wasted. As HVAC systems, chillers, or ventilation units operate, they generate exhaust air at temperatures typically between 25°C and 40°C (77°F to 104°F). This warm air is passed through a heat exchanger to transfer its heat to a separate water loop.
The water is preheated to around 35°C to 50°C (95°F to 122°F) before it goes into a boiler or heat pump, which means it takes less energy to bring the water up to the desired temperature of 60°C to 70°C (140°F to 158°F) for use. For campuses with round-the-clock HVAC operation and steady hot water needs, this technology turns what would be wasted energy into an incredibly valuable resource.
Educational institutions in the U.S. consume roughly 850–860 TBtu of energy annually, with academic buildings averaging between 18 to 20 kWh per square foot each year. Most of this energy consumption is related to space heating.
Energy costs range from about $1.50 to $3.00 per square foot annually – small schools might spend around $750,000 to $1.5 million each year, while large universities can see bills exceeding $20–30 million.
Many campuses are pursuing energy efficiency and renewable energy projects to reduce this financial burden. Air-to-water WHR is a crucial piece of this puzzle. By capturing excess heat and repurposing it to warm water, these institutions can slash their operational costs. Even a modest 10-20% reduction in energy use can free up funds for critical needs like textbooks, lab equipment, and larger infrastructure projects.
Carbon reduction
Campus facilities rely on substantial initial energy inputs, usually in the form of natural gas, to power their boilers and HVAC systems. These inputs contribute substantially to their carbon footprint. For example, an analysis of 537 UK higher education institutions found that campuses collectively released more than 18 million tonnes of CO₂ during 2020 and 2021 – roughly 2.3% of the nation’s entire greenhouse gas emissions.
Institutions around the world are setting ambitious goals to reach carbon neutrality by 2030 or 2050 by blending efficiency upgrades, renewable energy installations, and advanced management strategies – such as air-to-water waste heat recovery systems, high-efficiency boilers, and smart building automation.
T institutions are increasingly embracing sustainability not only as an operational imperative but also as a core element of their environmental, social, and governance (ESG) strategies. Colleges and universities wish to set a strong example to other organizations, communities, and their students by investing in initiatives that cut emissions and energy use. Waste heat recovery technology aligns with these goals.
Air-to-water waste heat recovery is a flexible solution that can be adapted to a variety of campus settings. It can be seamlessly integrated into boiler plants, boost hot water supply in residence halls and kitchens, and even support climate control in athletic and academic spaces. Here’s a closer look at some of the many applications:
Central boiler plants are usually housed in dedicated 5,000- to 10,000-square-foot spaces. These boilers are responsible for heating across campus. Retrofitting these plants with ATW recovery units allows for the recovery of latency heat during the condensation phase. This preheats boiler feedwater to improve combustion efficiency and lower fuel usage.
Residence halls typically range from 15,000 to 25,000 square feet and house anywhere from 150 to 300 students, all of whom rely on a 24/7 supply of hot water for showers, sinks, and laundry.
By installing ATW WHR modules on HVAC exhaust ducts, waste heat from the continuous ventilation can be captured and used to preheat water in a dedicated buffer tank. This reduces the load on central boilers during peak morning and evening periods.
Large campus cafeterias, with kitchens spanning 1,000 to 3,000 square feet, prepare and cook large volumes of food throughout the day. These kitchens are constantly generating waste heat that is being lost through kitchen ventilation systems. If this heat is captured by an ATW heat exchanger, it can be used to preheat circulating water used in dishwashers and other areas of the cafeteria, such as mop sinks.
Athletic complexes such as indoor gymnasiums, swimming pools, and locker rooms can cover 20,000 to 50,000 square feet. Swimming pools require water in the range of 27-29°C (80-84°F), while showers need 40-45°C (104–113°F).
ATW WHR systems can be installed on air handling units (AHUs) and dehumidification units within these facilities to collect the extra heat from the ventilation system. For instance, in an indoor pool facility, heat from dehumidifiers can be reclaimed to supplement pool water heating or preheat water for showers in adjacent locker rooms.
Academic buildings with large classroom blocks rely on centralized HVAC units (usually RTUs) to maintain comfort during daytime peak occupancy periods. Air-to-water heat exchangers can be retrofitted into air handling units to capture heat from exhaust air streams. The recovered energy can then be used to preheat water for fan coil units. This ensures a stable indoor temperature while reducing the dependence on primary heating sources.
Institutions can access a range of financial incentives to help offset the initial costs of ATW WHR systems:
Webinar provided introductory information for local governments eligible for the EECBG Program:
When you look at the whole picture, ATW WHR is actually very economically viable. Although the upfront costs may be an initial deterrence, these systems typically pay for themselves in two to five years by reducing fuel consumption by 5 to 10%. Beyond the quick ROI, campuses continue to save money on energy costs over the long term while contributing to carbon reduction and sustainability.
Air-to-water waste heat recovery is not a trend. It’s a practical engineering solution that is continuing to gain traction in the energy efficiency sector, and it’s well-suited to the unique challenges of educational campuses.
As energy costs continue to rise and institutions strive to meet their climate goal, this technology delivers measurable benefits through lower utility bills, reduced emissions, and increased environmental stewardship.
ENERVEX is a leader in ATW waste heat recovery solutions. ENERVEX’s VHX Economizer utilizes modular hybrid micro-channel and plate exchanger technology to convert waste heat into valuable hot water for diverse applications. With a payback period that typically runs less than two years and minimal downtime needed during installation, it’s a great option for educational institutions to stretch underfunded budgets.