Is Natural Ventilation Really Exists for Buildings ?

We breath oxygen and exhale carbon-di-oxide (CO₂), this is called the respiration process. When we are indoors, the level of CO₂ in the air increases due to the respiration cycle. Along with CO₂, body odor, moisture and other pollutants within the house make the air inside stale. Breathing stale air is unhealthy. To maintain freshness in space, the stale air must be replaced by fresh air regularly. Fresh outdoor air, is taken from the external environment, and the replaced indoor air in turn carries away with it the pollutants from inside your home. This process of replacing stale air inside your home with fresh air from the environment outside through windows and door openings, without the use of fans is Natural Ventilation.

Almost all historic buildings were ventilated naturally, although many of these have been compromised by the addition of partition walls and mechanical systems. With an increased awareness of the cost and environmental impacts of energy use, natural ventilation has become an increasingly attractive method for reducing energy use and cost and for providing acceptable indoor environmental quality and maintaining a healthy, comfortable, and productive indoor climate rather than the more prevailing approach of using mechanical ventilation. In favorable climates and buildings types, natural ventilation can be used as an alternative to air-conditioning plants, saving 10%–30% of total energy consumption.

In hotter places natural ventilation also help bring the room temperature down. This cooling effect can help reduce use of fans, coolers and avoid air-conditioners to significantly bring down your energy bills. You can employ the following strategies to improve the natural ventilation in your home:

• • We can design openings (such as windows) in your home’s building envelope so that they are in the path of wind flows from outside.

• • These openings must be placed at a suitable height in the direction of the natural breeze outside your home to allow air to flow through your rooms at body level to help make you feel more comfortable.
    
    Winds flowing at suitable height improve comfort

• • Place windows to facilitate wind circulation throughout the space. When wind flows in from one side, circulates through the space and exits from an opposite side, it is called Cross Ventilation. Cross Ventilation improves ventilation by distributing the flow of air throughout the space.
    
    Strategies to improve ventilation through appropriate window placement

• • You can enhance the flow of air inside your home by using ‘jaalis’ (lattice wall) and ventilators. Smaller windows funnel air into your home. Air passing through these small windows speeds up towards a larger opening in the opposite wall that serves as an exit. This engineered wind flow makes your home cooler. Traditionally, this was practiced in hot climates with ‘jaalis’. ‘jaalis’ are small apertures, that aid in accelerating passing wind passing to enhance ventilation.
    
    Winds speed up as they pass from smaller to larger windows.

• • High openings such as clerestory windows and ventilators act as effective exhausts for the hot air that accumulates near the ceiling of your home. Warmer air is lighter than cooler air, and therefore it rises up. This concept of rising hot air is called the Stack effect.
    
    Windows near the ceiling aid in removing accumulated hot air.

In humid climates such as in Coastal regions, ventilation can bring in much needed relief, because cool breeze replaces moist warm air faster away from our bodies causing the sensation of comfort. In desert like climates, natural ventilation can bring in unwanted heat as well which can cause discomfort. Wind passing over water bodies or through ‘khus’ pads, like in desert coolers, can provide cooler air. In colder areas, cold winds can cause discomfort. Obstructions around the house may be used to slow the cold winds. In the plains, which see both hot summers and cool winters, the in-between period is especially suited for natural ventilation when ‘Natural cooling’ can help avoid use of air-conditioners.

Naturally ventilated buildings should be designed to provide thermal comfort, to achieve adequate moisture and contaminant removal, and to meet or exceed Government Energy Conservation Performance Standards.