A very important strategy to stop heat gain and unwanted
direct sunlight is to divert sun's rays before entering the building.
This can be accomplished through the use of fixed and adjustable
shading. The most important consideration is the orientation of
the aperture which is being shaded. South-facing windows are easy
to shade, because in summer months, when shading is necessary, the
angle of the sun is high. However, east and west facing windows
are much more difficult to shade because the sun is much lower in
One example of shading is an overhand above fenestrations.
The length of the overhang must carefully consider sun angles in
both winter and summer so as not to block valuable solar gains in
the winter. The image below shows an example an excel worksheet
designed to recommend overhand depths depending on time of day,
year, and orientation developed by MIT student Sephir Hamilton.
The goal was to provide designers with tools to size such shading
devices. The example below shows solar radiation though a west-facing
window with 100% depth overhang and a 10% fin depth on June 21.
In addition to fixed shading devices such as overhangs,
we have also considered the use of adjustable shading devices, such
as curtains, blinds, and shutters. It is important that screens
provide adequate shading while still allowing daylight to penetrate
into the rooms. These shading devices can be useful in the winter
to add to thermal insulation as well as in the summer as a shading
device. It is recommended to place these to the outside of the glazing
to reflect unwanted solar gains before reaching the glazing layer.
Special glazing can provide an alternative to fixed
and operable shading devices. Such examples are reflective and absorbing
glass, but few of these are used on the residential scale. Another
alternative to shading devices is shading from vegation or nearby
buildings. Ideal plants will maximize protection from solar gains
in the summer, while providing minimum shade in winter months.
Chinese designers would like to include natural ventilation
in the design of their new buildings. This is a complicated issue
that involves the design of building interiors and window placement
to facilitate airflow. In addition, the proximity of neighboring
buildings and the building shape will influence air circulation
outside the building and in turn natural circulation throughout
the building. There is the desire to include natural ventilation
in high-rise buildings, a difficulty compounded by the interaction
of buoyancy and wind driven flows. If natural ventilation could
properly be designed in a building, our initial simulations suggest
that natural ventilation combined with nighttime cooling and thermal
storage in the walls would eliminate most of the need for air conditioning
in Beijing on an average summer day.
see natural ventilation
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