Conservant Systems · July 2026 · 3-minute read
Walk the air path in a conventional dehumidifying air handler on a humid day. Outside air arrives at, say, 85°F and 70% relative humidity. To get the moisture out, the cooling coil drags it down to roughly 55°F — well below the temperature anyone wants at the diffuser — because condensing water out of air requires cooling below the dew point. Then, because 55°F air would freeze out the occupants and drive space humidity up as it warms passively, a reheat coil burns natural gas, hot water or electric strip heat to bring it back to ~72°F.
You paid the chiller to remove heat, then paid the boiler to put heat back into the very same air. On a worked example from the HEDS Design Guide — a 4,000,000 BTU cooling load with a 1,000,000 BTU reheat requirement — the conventional configuration buys 5,000,000 BTU of total coil load to deliver 4,000,000 BTU of useful conditioning. And boiler efficiency in reheat service often runs below 70%, so the metered waste is worse than the coil math.
Why nobody fixed it for 100 years
Because the two halves of the waste live in different budgets. The cooling waste hits the electric bill; the reheat hits the gas bill; and the design "works" — spaces stay comfortable — so the flaw hides inside normal operations. Workarounds like desiccant wheels, enthalpy wheels, and heat pipes attack pieces of the problem but bring their own taxes: exhaust air streams, regeneration heat, moving parts that fail, and 75%+ higher air pressure drops.
The fix: recover the energy on both sides at once
The heat the chiller extracts doesn't have to go to the cooling tower. In the HEDS configuration, an oversized cooling coil lets the chilled water leave warm — 63–75°F instead of ~55°F — and that warm return water flows through a second coil that reheats the supply air. Every BTU the recovery coil moves does double duty: it's reheat you didn't purchase and load the chiller never sees returning. One water loop, two coils, both bills drop.
In DoD ESTCP field testing, reheat elimination was 100% in every single test case — operating rooms, clean rooms, dining facilities, barracks, labs and offices alike.
That's the physics behind numbers that otherwise sound impossible: 79% annual electrical savings measured at the Timken Museum, 77% daytime savings at Naval Base Guam, $927K first-year savings at Naval Weapons Station Seal Beach. When the waste is structural, removing the structure removes the waste.
Want the deeper engineering? The coil selection, hydronics and part-load behavior are documented for skeptical engineers — including where HEDS doesn't make sense.