Window Design for Daylighting

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Window Design

For

Daylighting

Lighting & Acoustic

B.Arch - 2

nd

Year

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Effectiveness of Windows for daylight

depends on :

1. Weather & Location

2. Room Proportion

3. Room Reflectance

4. Building Massing & Shape

5. Ceilings

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ROOM PROPORTION

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ROOM REFLECTANCE

Light distribution is highly dependant on

room reflectance, primarily walls and ceiling.

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BUILDING SHAPE AND MASSING

When using sidelighting only,

in general, a narrow form has the greatest access

to exterior openings and will be the easiest to illuminate.

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CEILINGS

In general, ceilings are the most effective light-reflecting and

light-receiving surfaces. It should be unobstructed, of high

reflectance, and “seen” by most horizontal task areas.

1.Increase the distance between

task and ceiling to allow the task

to “see” more ceiling.

2. Increase the distance between

light source and ceiling to

distribute light more evenly

across the ceiling.

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CEILINGS

3. Use low windows and

ground-reflected light, but be careful to avoid

glare at eye level.

4. Use high-reflectance

Surfaces.

5

. Shape ceiling for

min. surfaces and use

smooth surfaces.

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Design Issues for Side lighting through

Windows :

1. Location of Openings

2. Shape of Openings

3. Number of Openings

4. Shading Devices

5. Sunlight Redirecting Devices

6. Shutters, Blinds, and Screens

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Openings

The location of openings affects both light distribution and the

perception of distribution.

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Openings-Upper Section

The upper window sees the brightest zenith of the overcast sky and

therefore has the best distribution of light on overcast days. Upper

windows have potential for sun and sky glare so should be

properly baffled.

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Openings-Middle Section

The middle window is not optimal for light distribution on sunny

days or overcast days, yet it is the most commonly used location

because of the view afforded. Again,

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Openings-Lower Section

The lower window provides optimal distribution of reflected sunlight. This is because it maximizes the distance between the light source and

the ceiling and provides the greatest uniformity. The lower window will typically not be a source of direct glare, but can be a source of

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Openings-Lower Section

The value of the view out a low window depends on its scale. The

view from the bottom third of a 24-foot wall can be very good, but

the view from the bottom third of a 9-foot or 12-foot wall with

the window head only 3-4 feet above the floor is likely to be

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Openings-Near Interior Walls

Vertical high-reflectance walls can also be utilized as a surface to receive and redistribute sunlight. These windows will encourage distribution while

minimizing shadows, and reducing glare and contrast between the opening and the interior. Walls are especially useful for controlling low-angle (horizontal)

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Shape of Openings-Displacement

1. Projecting lower sills will maximize illumination from area sources such as overcast skies. It should be used in orientations that do not require shading.

2.The overbite configuration is best for ground-reflected sunlight and shades direct sun and skylight.

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Shape of Openings-Walls

Sills which slope to the exterior will minimize the possibility of glare

from the sill and will allow penetration of ground-reflected light.

These sills are not good at reducing contrast on the interior or

bouncing light deeply into space.

Sills which slope or curve on

the interior will create intermediate gradients of light that effectively

soften a contrast between interior and exterior. They can also bounce

light deep into a space.

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Multilateral Openings

In general, locating openings in more than one wall will enhance the distribution of light. Light coming from multiple directions helps provide a softer, more diffuse light with less shadows and

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Shading Devices-Horizontal

Horizontal devices provide shade based on the altitude angle of the sun. They let in low-angle sunlight and block high-angle

sunlight; their effectiveness varies seasonally with the changing solar altitude.

Most commonly seen in the form of overhangs, they are particularly effective for shading north and south elevations.

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Shading Devices-Vertical

Vertical devices provide shade based on the bearing angle of the sun. Their effectiveness varies diurnally, as the sun moves around the

horizon.

Vertical devices have the ability to block low-angle sun, and consequently they are often used on openings facing east or west

.

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Shading Devices-Egg-Crate

Egg-Crate shading devices combine the characteristics of vertical and horizontal devices to improve the shading coverage.

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Sunlight-Redirecting Devices-Light Shelves

Light shelves are horizontal shading and redirecting devices. They effectively create two apertures in a window wall, an upper clerestory window which is primarily for illumination and a lower window for view

.

For best distribution, light shelves should be located as low in a space as possible without causing glare, typically above standing eye level.

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Sunlight-Redirecting Devices-Light Shelves

To be effective, the minimum depth of a light shelf is determined by

shading requirements. To prevent glare conditions, direct light from the

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Sunlight-Redirecting Devices-Light Shelves

The location of the glazing affects the amount of solar radiation admitted into a building. Recessed glazing has shade throughout the year; glazing

flush to the exterior maximizes heat gain. For buildings with seasonal heating requirements, the glazing should be located midway.

Note: light shelves are most effective on the south side. To achieve effective shading, on the east and west sides they can be augmented with vertical devices, or additional horizontal louvers. Light shelves are not useful for light distribution on the north side, but they do not

substantially

reduce illumination and may make views more comfortable by blocking sky glare.

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Sunlight-Redirecting Devices-Suncatchers

Suncatchers are vertical sunlight-redirecting devices parallel to the

building façade. They are best for intercepting low-angle sunlight

on the east and west sides of buildings. They also catch sunlight on the

North side of buildings, substantially increasing the illumination.

Note: light which they “catch”

tends to be reflected downward, which can result in glare.

Therefore,

they should be used to redirect light

toward walls or, in conjunction with

a light shelf, to redirect the light toward the ceiling.

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Shutters, Blinds, And Screens

Shutters, blinds, and screen do not redirect light; they only diffuse or reject it. They have the advantage of being movable which allows

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Five Basic Strategies to Promote

Effective Use of Daylight :

1. Maximize solid angle of sky seen from the task

2. Shade to prevent glare

3. Do not block light

4. Locate openings high

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Five Basic Strategies to Promote

Effective Use of Sunlight :

1.Shade to prevent glare and excess heat

1.Indirect sunlight where it is needed

2.Control the amount of light entering in a space

3.Use the light efficiently

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Light tube

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Assignment No. : 2

Q1. Explain the concepts adopted, the benefits, the design

recommendation , the materials used and the methods of construction for an effective Daylighting design.

Q2. Describe with sketches strategies that you would use for distribution of

daylight in the interiors of a multi level office building.

Q3. With the help of a diagram, explain admission of diffused light in an

industrial building.

Q4. Mention the criterias considered while designing daylighting. Elucidate

with examples, the benefits of daylighting with materials and methods used as design considerations and recommedations.

Q5. Mention and explain the lighting design strategies that an architect