Natural ventilation operable windows/ shades

·         The feasibility of natural ventilation strategies depends on

1.      local air quality

2.      climate conditions

3.      building layout

4.      greatly influenced by floor plan depth

5.      other factors

·         Offer fresh air flow without the need for energy input.

·         Occupants value the psychological benefits of a connection to the outdoors, especially if they can control it by simply opening a window.

v  Casement and projecting windows can typically be fully opened, allowing for greater ventilation. An outward-projecting sash may help direct outdoor air into a room. Under harsher wind conditions, however, inward-projecting sashes may be more feasible.

v  Sliding windows have more limited openings of less than half of the overall window area.

v  Mechanically or manually operable skylights or roof windows allow rising warm air to exit and be replaced by cooler outdoor air entering through open windows at a lower level.

Window placement (location and size of opening) will affect occupant cooling if air is moving fast enough. The average interior air velocity is a function of:

• the exterior wind velocity;
• the angle at which the wind strikes the opening;
• and the size of the opening.

Benefits

·         cost and environmental impact of energy use

·         Not only does natural ventilation provide ventilation (outdoor air) to ensure safe healthy and comfortable conditions for building occupants without the use of fans, it also provides free cooling without the use of mechanical systems.

·         building construction costs and operation costs

·         reduce the energy consumption for air-conditioning and circulating fans

Disadvantages of Natural Ventilation

·         lack of precise control of air flow, which only fan ventilation can insure

·         dependant on the difference between inside and outside temperature but mostly on the wind, which can change in both speed and direction every few minutes

·         building  runs the risk of underventilation on calm, hot days and overventilation on cold days.

·         building location where wind would be deflected or blocked is unacceptable for a natural system

http://www.commercialwindows.org/ventilation.php

http://gbtech.emsd.gov.hk/english/utilize/natural.html

http://www.ides-edu.eu/wp-content/uploads/2013/04/Ventilation_lecture-2_PH-Alleen-lezen.pdf