Monday, April 4, 2011

Ventilation Controls


As buildings become increasingly airtight, awareness of mechanical ventilation grows. Proper ventilation is essential for removing excessive moisture that promotes mold and mildew buildup, which can deteriorate a building's structure. Mechanical ventilation also helps remove accumulated volatile organic compounds (VOCs) that affect indoor air quality (IAQ) and may cause health problems for occupants.

Different lifestyles place different demands on the ventilation system. For example, a single adult, most likely, will require less ventilation than a family of five with pets. Also, an adult homeowner may be more likely to properly operate a manual ventilation control than a tenant or children that share a bathroom. Therefore, selecting a suitable control that runs ventilation at the proper time and duration will ensure that both the occupant's health and building structure are protected.

There are several types of manual and automatic controls that can be applied to ventilation systems. Some controls are more suitable for intermittent or continuous ventilation. Panasonic's new WhisperGreen® Premier fans incorporate built-in speed, delay and occupancy controls, making them ideal for both intermittent and continuous ventilation. The following discusses options to help select a suitable control.

Manual Controls:
Manual controls require the occupant to activate the ventilation fan when needed. This allows people who are particularly sensitive to indoor air quality to manually control and maintain their comfort level. The disadvantage of manual controls is that some people may not sense the need for ventilation and not turn it on. The basic manual control is an on/off toggle switch. However, there are other controls with functions that may be more suitable to the occupant's lifestyle.

Delay timer:
Shower curtains, towels, walls and cabinets retain moisture long after the occupant has finished and left the bathroom. The advantage of a delay timer is that it continues to evacuate moisture and odor after the occupant has finished. WhisperGreen® Premier fans incorporate a delay timer that can be set within the range of 30 seconds to 60 minutes for the desired delay effect.

Manual timers:
There are two basic types of manual timers. The less expensive are spring-wound, known as crank timers, suitable for intermittent bathroom ventilation. Electronic timers are more decorative and expensive but allow the occupant to select a time duration with the push of a button. Electronic timers do not produce the sometimes annoying ticking sound that crank timers are known for. WhisperGreen® Premier fans incorporate quiet electronic controls.

Speed controls:
Speed controls allow the user to set the desired speed (airflow) of a ventilation device. Speed can be controlled either continuously or in steps. One of the disadvantages of speed controls is that they can cause undesirable noise when working in conjunction with the fan's AC motor. WhisperGreen® Premier fans incorporate a DC motor that operates quietly with its own built-in controls.

Automatic Controls:
These controls can be full or semi-automatic. An example of a fully automatic control is a 24-hour duty cycle timer that is programmed to cycle on and off over a 24-hour period. A semi-automatic control is a control that has an override switch. An example would be an occupancy sensor with a manual on/off override.

Occupancy (motion) sensors:
Occupancy sensors are suitable for intermittent ventilation. An advantage is that the ventilation system will operate without having to rely on the occupant's interaction. The ventilation system will remain "on" and continue working for a duration after the occupant has left the room, much like a delay off timer. Select WhisperGreen® Premier fans have occupancy sensors integral to the fan grille. Dehumidistats can be used to turn a ventilation system on/off when relative humidity reaches a certain level. These controls are most likely to be used in bathrooms to evacuate excessive moisture. Dehumidistats have a few disadvantages. One disadvantage is that seasonal changes in outdoor relative humidity necessitate seasonal readjustments to function optimally. Another disadvantage of a dehumidistat is that they are often mistaken for thermostats and set at 70 and never adjusted. Finally, it does not automatically remove odors.

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