Passive ventilation

Passiveventilation

The cooling energy consumption can be up to 20% of the total energy demand of the building, and in warmer regions it can be more. Therefore it is beneficial to decrease the energy demand for cooling by using natural ventilation.

Another aspect must be considered is that conventional buildings mostly rely on mechanical air conditioning systems which contribute to larger energy consumption and frequently cause indoor air quality (IAQ) issues. Most newly built houses are airtight due to energy saving requirements. However, reduced air permeability leads to insufficient air exchange through infiltration, resulting in a negative impact on the health of the occupants.

According to the U.S. Environmental Protection Agency (USEPA) indoor air pollution is among the top five environmental health risks. Since people spend on an average of 80–90% of their time working and living indoors it is vital to maintain the indoor environment in a good quality. Poor air quality, can potentially cause “Sick Building Syndrome” and also metabolic diseases which are 30–200% more frequent in air-conditioned buildings.

On the other hand, in naturally ventilated buildings there are no issues of SBS and the occupant comfort and satisfaction is higher. Another important aspect is that, it it is estimated that naturally ventilated buildings cost about 10-15% less to construct than airconditioned buildings.

Therefore, natural ventilation has several purposes, such as:

 improving the indoor environmental quality,  providing fresh air for breathing and  providing passive cooling and control of the indoor temperature and the relative humidity.

Ventilation in general means that there is an air exchange between the building and the outdoors. According to the ASHRAE Handbook of Fundamentals:

“Air exchange of outdoor air with the air already in a building can be divided into two broad classifications: ventilation and infiltration.

 Ventilation air may be induced as: - forced - natural ventilation, - infiltration, - suitably treated re-circulated air, or an - appropriate combination.

Natural ventilation is the flow of air through open windows, doors, grilles, and other planned building envelope penetrations.

Forced ventilation is the intentional movement of air into and out of a building using fans and intake and exhaust vents.