Maximize
Natural Ventilation
Windows should
be designed to admit natural ventilation. The most important design
issue is whether the windows provide single-sided or cross-ventilation
to interior spaces.
The amount of
air that flows through a window (ventilation capacity) depends on
the area and vertical distribution of openings. These depend on the
way the window opens.
Horizontal pivot
windows offer the highest ventilation capacity:
- For single-sided
ventilation, place them as high as possible to exhaust warm air
at ceiling level.
- Air entering
through the upper opening is directed toward ceiling, making night-time
cooling more effective.
Center vertical
pivot windows have less ventilation capacity than horizontal pivot
windows, but can act as wind scoops when wind direction is parallel
to the building face.
Casement windows
offer the same advantages as vertical pivot windows but are susceptible
to gusts. If using casements to channel wind:
- Open into prevailing
winds when used as inlets.
- Open away from
prevailing winds when used as outlets.
If not part of
the window design itself, incorporate fins, overhangs or articulation
to create high and low wind pressure areas, and to channel incoming
air.
- Use vertical
fins to improve natural ventilation of rooms with only one exterior
wall. Provide two separate operable windows on upwind and downwind
sides of fins, for inlet and outlet.
- Articulate
the building facade (e.g., with bay windows) to create localized
pressure differences. Place windows on adjacent or opposite faces
of the protrusion as inlets and outlets.
Noise is a common
irritant in the workplace and can be caused by sound transmission
paths through windows. It is typically most severe on the first three
floors of urban buildings, or near major streets. Windows on affected
exposures of the first three floors should have a Sound Transmission
Class (STC) of 35 or better. Sound leaks through cracks normally establish
window noise ratings regardless of glazing.
- Block direct
path of sound travel. Sound transmission through an “open”
window can be reduced by 25%. by specifying the opening to redirect
noise.
Often windows
required for view and day-lighting are not in appropriate locations
for effective natural ventilation. Here, it may be appropriate to
incorporate operable vents specifically located and designed to admit
controlled amounts of ventilation air.
Cautions
- Vertical fins
used to redirect winds may restrict views. Transparent fins function
as well, but are expensive.
- Carefully consider
the effects of adjacent buildings on site wind flow patterns. Complex
locations and buildings may require model wind tunnel testing.
- If operable
windows are used for ventilation, window sensors should be used
to shut down the mechanical cooling system, if any.
- Consider maintenance
and cleaning of operable windows and the use of blinds.
