It is generally accepted, and has been confirmed by studies, that humidification of dry indoor air to raise relative humidity (RH) during the heating season is beneficial to the comfort and health of building occupants. Humidification also prevents adverse effects on wood floors and furniture and reduces static electricity buildup which can harm electronic equipment.

Currently, the most widely used residential humidification technologies are forced air furnace mounted bypass wetted media, spray mist, and steam humidifiers. These use city water as a water source and require additional furnace heat or electricity to evaporate the water, which consumes 4% or more of the furnace fuel input. Mineral deposition, white dust and microbial growth problems are associated with these humidifiers. For commercial building humidification, demineralized water is typically used for humidification equipment such as steam heat exchangers, electric and ultrasonic humidifiers, compressed air atomizers, and high pressure cold water foggers. In addition to the energy consumption for the water evaporation, energy is also needed to produce high-quality demineralized water through a reverse osmosis process.

A Transport Membrane Humidifier (TMH) technology was developed by using nanoporous membrane capillary condensation separation mechanism to transport water vapor only from furnace combustion flue gas to humidify building air. After proving the technology in a laboratory environment for an equivalent 4-year operation, two TMH units were installed for two home furnaces with AFUE ratings of 80%. The two furnaces are from two different manufacturers with different ductwork configurations and different heating capacities, so two separate designs were made to accommodate the difference. Both TMH units had been in operation through the 2010-2011 and 2011-2012 heating seasons in Chicago area homes, and provided satisfactory whole house humidification with both occupied homes maintained at 40 to 60% RH. At the same time, they boosted the two furnace's efficiency from around 80% to more than 95%, providing significant energy savings. Compared with conventional whole house humidification technology, the TMH humidification benefit comes with no water connection, no need to change filters/wetting pads/drums, no white dust to rooms, and no bacteria growth concerns from standing water. In addition no maintenance is required for the TMH units.