Ventilation Systems in Buildings

Oversight

• The Environmental Protection Agency delegates responsibility for monitoring and regulating indoor air quality to each state. Along with other standards, each state has rules related to the installation, inspection, testing, and maintenance of building ventilation systems in homes, businesses, and other settings. Once the ventilation systems are in place, building owners must properly maintain the units and keep them in good operating condition. Most codes don't guarantee good air quality but rather outline the type of ventilation system a property owner must install during new construction and for remodeling projects. The Occupational Safety and Health Administration has the authority when it comes to ventilation standards in the workplace. OSHA is concerned with airborne toxic chemicals, flammable vapor, other hazards, and replacing the hazard with clean air.

Natural Ventilation Systems

• Building owners select natural ventilation systems for maintaining clean, healthy, and comfortable air quality. It's not unusual for older buildings to have natural ventilation systems, which rely on wind and buoyancy to produce pressure variance due to differences in humidity and temperatures. The size and place of openings in these buildings determine the amount of ventilation. A combination of windows, transoms, grilles, and open floor space work in tandem to circulate air throughout the building. Natural ventilation systems function like a circuit where air supply and air exhaust have equal significance. Fresh air flows in and stale air flows out. Many structures have accidental "natural ventilation" systems because of air leaks through the exterior walls.

Supply Ventilation Systems

• Supply ventilation systems are types of mechanical ventilation systems that work in both hot and mixed-temperature climates. They employ fan and duct systems to pull air through intake vents. The system distributes the air to different spaces within the building through two methods. One method is to install a fan and two sets of duct dedicated to ventilation. The other approach connects an exterior air intake vent to the primary return air duct on a HVAC unit, which distributes clean fresh air. Attaching the duct to the main supply duct conditions exterior air before introducing it to the interior environment. Avoid installing this system in cold weather climates. To do so would pressurize the building and force heated air through leaks in the structure's envelope and potentially lead to problems with excess moisture.

Exhaust Ventilation Systems

• Typically installed in cold climates, exhaust ventilation systems continuously exhaust interior air to the exterior of the building. The system employs two or more fans to remove stale indoor air. Many bathrooms and kitchens have exhaust fans installed. Since exhaust ventilation systems tend to depressurize buildings, don't use them in hot humid climates because the units pull hot air through openings in the building wall. The hot air mixes with cool air causing problems with excess moisture.

Balance Ventilation Systems

• Designed for use in a variety of climates, balance ventilation systems transfer equal volumes of air in and out of the structure. Typically, the unit uses two fans -- one for each task. Select from two types of balance ventilation systems: energy recovery ventilation and heat recovery ventilation. The ERV systems transport heat and moisture between incoming and exhaust air. Decreasing the amount of moisture in the building reduces the need for a dehumidifier or air conditioning equipment during the summer months. In the winter months, HRV moves heat from exhaust air to incoming air. The system transfers incoming air to exhaust air during the cooling season.