Rooftop ERE water-to-air units can introduce a fixed amount of outside year-round or a modulating Economizer can provide free cooling when outdoor conditions are favorable. These units 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, etc.