The Environmental Protection Agency (EPA) and its Science Advisory Board report that indoor air pollution is among the top five environmental risks to public health. EPA studies show that levels of some indoor air pollutants can reach more than 100 times that of outdoor air pollutants. Indoor air pollutants such as dust mites, bacteria, and pollen come from almost everything in our homes including cleaning supplies, smoke, dust, molds, paint, carpets, drapes, upholstery, furnaces, gas burners, wood, and other building materials. Central air purification systems reduce the amounts of these particulates in indoor air.
Several companies now manufacture dehumidifying ventilators that provide fresh air induction that is filtered and dehumidified for residential applications. Typically, the equipment operates to provide fresh (outdoor) air when ventilation is needed through ductwork where it is mixed with indoor air drawn from the house and filtered prior to being delivered to the supply plenum of the central heating and cooling system. When only filtration is desired, dampers can be set to seal off the fresh air duct and some units simply re-circulate and filter indoor air. When dehumidification is needed, units can be set to operate at different humidity levels, treating either outdoor or indoor air, or both.
Dehumidification requires the use of energy, so, dependent on climate, it is sometimes more cost-effective to let the home’s central cooling system handle dehumidification during periods when both outdoor temperature and humidity are high. Dehumidification by ventilation and purification system is most useful when outdoor humidity is high, but temperatures are low enough to preclude cooling.
The dehumidification capability is unique to these systems. Other systems such as energy recovery ventilators transfer moisture between incoming and outgoing airstreams, but do not have a controlled dehumidification function.
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Filtering and dehumidifying fresh air before it is delivered to the living area may reduce the potential for aggravation due to allergies and respiratory ailments.
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Central air purification, ventilation, and dehumidification systems provide the capability to bring fresh air to a home environment and condition it without the use of an HVAC system. This can enhance occupant comfort during the months when heating and cooling are not needed and supplement the quality of the indoor environment when HVAC systems are engaged. Controlling humidity year round can reduce the potential for mold and mildew growth.
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In new construction applications units are typically installed by HVAC contractors. Installation should not change the critical path of a building or negatively impact labor time.
Units can be retrofitted in existing homes. Retrofit is most economical in homes that use forced air conditioning so that existing ductwork can be used.
The installed cost starts at approximately $2,000 and will vary with unit and features selected and trade contractor used for the installation..
Used instead of the whole house HVAC system, a dehumidifying ventilator may cost less to operate, than a forced air conditioning system. However, there will be an increase in energy usage when climate conditions require using the two systems in tandem.
There are no codes that restrict the use of these systems. However, they must be installed in accordance with residential mechanical codes. Some jurisdictions require the use of mechanical ventilation, but purification and dehumidification are usually not specified.
NREL, Residential Dehumidification Systems Research for Hot-Humid Climates  (1.5MB)
It is recommended that an HVAC contractor or builder install the unit next to the air handler or in the attic. It can be installed on new or existing equipment.
Therma-Stor offers a 1-year limited full product warranty and a 5-year limited warranty on parts of the product (condenser, evaporator, and compressor).
Ventilation systems can help to improve indoor air quality by diluting indoor air pollutants. The Therma-Stor system offers the benefits of tempering, de-humidifying, and filtering the outdoor air before it is delivered to the living space. The de-humidification capability is most advantageous in climates where there are frequent periods of high outdoor humidity, but not necessarily concurrent high temperature.
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