daylighting and natural ventilation

1. K saad ahmed
Msajaa

2.  The size and orientation of windows and
skylights control the quantity and quality of
natural light that penetrates and illuminates
an interior space.
 Window size is obviously related to quantity
of light.
 The quality of light—its intensity and color—is
determined by a window’s orientation and
placement in a room.

3. Window Clerestory
Window wall Skylight
Bright areas of light
attract
attention
Indirect daylight
can be used
effectively as task
lighting.
Changing
patterns of light
and
shadow animate
space.
Light can be
used to define
space.

4.  Natural ventilation relies on the natural movement of air
rather than mechanical means, and is an important
component of sustainable design. Wind velocity,
temperature, and direction are important site
considerations in locating windows in all climatic regions.
During hot periods, wind-induced ventilation is desirable for
cooling by evaporation or conduction. In cold weather,
wind should be avoided or screened from windows to
minimize the infiltration of cold air into a building.
At all times, some degree of ventilation is desirable for good
health and the removal of stale air and odors from interior
spaces.
 Natural ventilation in interior spaces is generated by
differences in air pressure as well as temperature. Airflow
patterns induced by these forces are affected more by
building geometry than air speed.

5. Natural ventilation requires the use of operable
windows.
High inlets
and
outlets
produce
air
movement
above our
body
level.
Lowering
the outlets
does not
ameliorate
this
condition.
Air flows
from
higher to
lower
pressure
zones.
Air flow
is
accelera
ted
when
inlets
are
smaller
than
outlets.
Louvers can help direct air flow.
Interior partitions and tall furnishings can adversely
affect the pattern of air flow.

6. Even when closed, windows are sources of building heat
gain and loss.
Heat gain helps save heating energy in cold weather but
increases cooling energy use in hot weather.
Heat gain is due to solar radiation passing through a window’s
glazing. Heat loss through a window wastes energy in cold
weather as a result of the temperature differential
between a heated interior space and the colder outside
air.
Glass is a poor thermal insulator. To increase its resistance
to heat flow, a window can be double- or tripleglazed, so
that the trapped air space between the glass panes can be
used as insulation. The air space can be filled with an
insulating gas, usually argon or krypton, to reduce heat
transfer further. For improved thermal efficiency, tinted,
reflective, or low-emissivity (low-e) glazing can also be
used.

7. Heat flows from warmer to cooler
zones.
Double- or triple-glazing traps air
space to increase a window’s thermal
insulation value.
To control heat loss, minimize
window openings that face cold
winter winds, or buffer them
with landscaping elements.
A window’s orientation is a more cost-effective factor
in controlling solar radiation than is its construction.
A sunspace is a glazed area oriented to admit large
amounts of sunlight. Massive materials store thermal
energy for later release. Some operable glazing is
necessary to ventilate the space in warm weather.

8. In addition to their aesthetic impact on the interior environment,
windows influence the physical arrangement of furnishings within a room.
Their brightness during daylight hours and the views they offer attract our
attention and encourage us to orient a furniture grouping toward them.
When locating windows, the designer should consider whether the
size and proportion of wall segments between them can accommodate the
desired furnishings. If wall space is at a premium, clerestory windows and
skylights can be considered as alternatives.
The sill height of a window affects what can be placed below it. A
low sill height may dictate that the floor area in front of the window be
left open, thereby reducing the amount of usable floor space in a room.
This is especially pertinent when window walls extend down to the floor to
promote visual continuity between interior and exterior space.
Other considerations in the placement of furnishings near windows
include the adverse effect the heat and glare of direct sunlight can have
on a room’s occupants, and the possible fading and deterioration of its
carpet and other furnishings.

9. Position windows to consolidate wall space.
Clerestory windows and skylights provide daylight
while conserving wall space.
Windows should be coordinated with built-in
elements, such as countertops and stairways.
Windows expose the backs of furniture
placed against them.
Window walls that extend to the floor inhibit
the placement of furniture against them.