Hydron Module Commercial Rooftop ERE water-to-air units can provide a set amount of outside air year-round or when outdoor conditions are right, a modulating Economizer can provide free cooling. These models are designed for an extended range of source water temperatures, which makes them suitable for closed-loop or ground-source closed loop systems. Exceeding ASHRAE 90.1 efficiencies (40 percent better than standard rooftop units), these systems are ideal for large commercial buildings, public institutions, schools, and more.