Indoor Air Quality
Ventilation Control Systems
Increase energy efficiency, reduce moisture condensation problems, and increase indoor air quality
Today's energy efficient homes do a great job of keeping conditioned air in. But, the downside of a well air sealed and insulated home is that reduced stale air exhaust and air exchange with the outside can result in poor indoor air quality which may lead to occupant health and structure durability problems. Even air systems that are designed with a fresh air intake do not provide ventilation or exhaust when they are not operating.
Economical and affordable ventilation controls are ideal for use with exhaust or supply fans, air handlers, heat recovery ventilators, intermittent whole-house exhaust systems, or anywhere specific ventilation rates are desired. Mixing the house air with fresh outdoor air can reduce concentrations of moisture and contaminants indoors and recharge the indoor air’s oxygen content.
There are many types of ventilation controls that including the simplest devices - manually operated twist-timers. Some of the controls that are available to automatically operate mechanical ventilation systems that are integral to most homes are described here.
Programmable Microprocessor Exhaust Fan Controls
Microprocessor-based controls can balance ventilation with energy conservation because they can be programmed to operate intermittently. Different models allow for single or dual fan speed operation. For instance, a multi-speed exhaust fan might be operated by this type of control at low speed to provide ventilation and then boosted, via occupant use of the wall switch, to high speed when local high volume exhaust is desired for mist removal after a shower. These controls eliminate user error by automatically coordinating fan speed and cycle time based on the overall volume of air in the home and occupancy, while still allowing occupants access to a full-speed fan cycle. Controls can be paired with a quiet, energy-efficient fan so that occupants are not aware of the fan’s operation. Some units come with a battery backup that will hold the programmed setting during a power failure. Tamerack’s Airetrak™ is one example of a programmable microprocessor fan control.
Controllers for the Central Air Handler Fan
Central air handler fan controllers can be pre-programmed to engage the central system fan to periodically mix indoor air (when the system is not running) and to control a motorized damper in a fresh air supply duct that connects outside air with the system’s plenum. Controlling the system’s fan operation with a control that is independent of the thermostat avoids continually running the fan. The same control can be used to engage the fresh air intake duct damper. Otherwise, air intake dampers are often triggered when the system’s fan is in operation which can over-burden a system in extreme hot or cold climates. AirCycler™is one such control.
Integrated Exhaust Fan and Microprocessor Control Systems
An integrated ventilation system, SmartSense®, is available as a kit that includes low sone exhaust fans and switches that can be installed in any room in a home. Once the system is in place and programmed, one switch becomes the master control and all others become slaves (via a phase coupler mounted near the circuit breaker panel.) The system can be operated with up to 10 slave switches. All switches can manually operate the local fan. The master can operate any given fan based on a pre-programmed ventilation level that factors in the manual use at each location.
: These systems introduce fresh air and/or remove stale air at timed intervals
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Central Air Purification/Ventilation/ Dehumidification Systems
Strategy to promote occupant comfort and good IAQ
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.
: 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.
: 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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