HVAC: Ventillation


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A lecture in the process of changing or replacing air in any space to provide high indoor air quality (i.e. to control temperature, replenish oxygen, or remove moisture, odors, smoke, heat, dust, airborne bacteria, and carbon dioxide).

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HVAC: Ventillation

  1. 1. HVAC: VENTILATIONA lecture series by Dr. Tomas Ucol-Ganiron Jr
  2. 2. VENTILATING-the process of "changing" or replacing air in anyspace to provide high indoor air quality (i.e. tocontrol temperature, replenish oxygen, or removemoisture, odors, smoke, heat, dust, airbornebacteria, and carbon dioxide).
  3. 3. VENTILATION-the intentional movement of air from outside a building to theinside.-includes both the exchange of air to the outside as well as circulationof air within the building.-one of the most important factors for maintaining acceptable indoorair quality in buildings
  4. 4. METHODS OFVENTILATING A BUILDING1. Mechanical or Forced Ventilation-is used to controlindoor air quality. Excess humidity, odors, andcontaminants can often be controlled via dilution orreplacement with outside air. However, in humid climatesmuch energy is required to remove excess moisture fromventilation air.
  5. 5. METHODS OFVENTILATING A BUILDINGKitchens and bathrooms typically have mechanical exhaust to controlodors and sometimes humidity. Kitchens have additional problems to dealwith such as smoke and grease . Factors in the design of such systemsinclude the flow rate (which is a function of the fan speed and exhaustvent size) and noise level. If ducting for the fans traverse unheated space(e.g., an attic), the ducting should be insulated as well to preventcondensation on the ducting. Direct drive fans are available for manyapplications, and can reduce maintenance needs.
  6. 6. METHODS OFVENTILATING A BUILDINGCeiling fans and table/floor fans circulate air within a room for thepurpose of reducing the perceived temperature because ofevaporation of perspiration on the skin of the occupants. Because hotair rises, ceiling fans may be used to keep a room warmer in thewinter by circulating the warm stratified air from the ceiling to thefloor. Ceiling fans do not provide ventilation as defined as theintroduction of outside air.
  7. 7. METHODS OFVENTILATING A BUILDING2. Natural Ventilation- is the ventilation of a building with outside airwithout the use of a fan or other mechanical system. It can be achievedwith open windows or trickle vents when the spaces to ventilate are smalland the architecture permits. In more complex systems warm air in thebuilding can be allowed to rise and flow out upper openings to the outside(stack effect) thus forcing cool outside air to be drawn into the buildingnaturally through openings in the lower areas.
  8. 8. METHODS OFVENTILATING A BUILDINGThese systems use very little energy but care must be taken to ensure theoccupants comfort. In warm or humid months, in many climates,maintaining thermal comfort solely via natural ventilation may not bepossible so conventional air conditioning systems are used as backups.Air-side economizers perform the same function as natural ventilation,but use mechanical systems fans, ducts, dampers, and control systems tointroduce and distribute cool outdoor air when appropriate.
  9. 9. TYPES OF VENTILATION1. Mechanical or Forced Ventilation-through an air handling unit or direct injection to a space by a fan. A local exhaust fan can enhance infiltration or natural ventilation, thus increasing the ventilation air flow rate.
  10. 10. TYPES OF VENTILATION2. Natural Ventilation-occurs when the air in a space is changedwith outdoor air without the use of mechanical systems, such as a fan.Most often natural ventilation is assured through operable windowsbut it can also be achieved through temperature and pressuredifferences between spaces.
  11. 11. TYPES OF VENTILATION3. Mixed Mode Ventilation or Hybrid Ventilation- utilizes bothmechanical and natural ventilation processes. The mechanical andnatural components may be used in conjunction with each other orseparately at different times of day. The natural component,sometimes subject to unpredictable external weather conditions maynot always be adequate to ventilate the desired space. The mechanicalcomponent is then used to increase the overall ventilation rate so thatthe desired internal conditions are met.
  12. 12. TYPES OF VENTILATION4. Infiltration-is separate from ventilation, but is often used to provideventilation air.