Unit heaters are a type of heating product that is designed to be installed within the heated space. They are typically used to heat open commercial spaces such as factories, warehouses, and garages, and are typically hung from the ceiling.
The Energy Policy Act (EPAct) of 2005 set the first national standards for unit heaters, and they took effect in 2008. The EPAct standards were based on standards that had previously been adopted by several states. The standards are prescriptive requirements that require that unit heaters be equipped with an intermittent ignition device and have either power venting or an automatic flue damper.
Typical gas-fired unit heaters generally have a thermal efficiency of about 80%, which means that 20% of the energy is wasted. Condensing unit heaters extract additional heat by condensing the water vapor in the flue gases and achieve thermal efficiencies of 90% or higher.