Shading Devices

SHADING DEVICES

A shading device is a component of a window and facade that protects space from direct sunlight, over heating, glare and provides increased day light, privacy or view to the outside.

Functions of shading devices.

• Well-designed sun control and shading devices dramatically reduce building peak heat gain and cooling requirements.

• These devices also improve the natural lighting quality of building interiors.

• Shading devices can improve user visual comfort by 991d controlling glare and reducing contrast ratios.

• Some shading devices can also function as They are called as light shelves, which bounce natural day light deep into building interiors.

• The use of shading devices is an important aspect of many energy-efficient building design.

• Sun shading devices inhibit the solar radiation (block, allow, etc.) incident on a building. They are used either internally or externally.

• They can be any mechanical equipment (like dynamic facades), projections (chajja), cantilevers, louvers, fins, jaalis or even textiles.

• They can be fixed, manual and automatic movable.

• The main objective is to create a comfortable internal environment. That is, cool in the summer and warm in the winter.

Importance of Sun Shading Devices

• Sun Shading Devices improve internal environment in order to provide greater comfort for occupants.

• Use of shading device can improve building energy performance.

• Shading devices can prevent glare (causing discomfort or disability of vision).

• They increase useful daylight availability.

• They provide a sense of security (internal sun shading devices like curtains help to beautify internal space and create a sense of privacy).

Solar shading

When sunlight hits a pane of glass, it splits into three components

Reflected: no effect on heating.

Absorbed: glass heats up which would transfer heat by conduction and also emits heat (and)

Transmitted: Heat up surface behind it.

The proportion between the three components is determined by the 'angle of incidence' and by the type of glazing.

For most types of glazing, the transmitted component is very small if the angle of incidence is larger than 45° from the normal to the glazing.

If the angle is more than 60°, most of the radiation is reflected.

1. Types of shading devices

Shading devices are classified into two types viz. (Fig. 1.25)

On the basis of their position in a building:

1. Internal shading devices

2. External shading devices

1. Internal shading devices

• Internal shading devices such as curtains, vertical blinds can reduce heat energy passing through a window. The effectiveness of these shading devices depend on their ability to reflect the incoming solar radiations back through the window. (Fig. 1.25 (a))

• Light coloured drapes or blinds lined with light coloured materials are more effective than the dark coloured shading devices.

• The major disadvantage of internal device is that they awobar trap heat on the interior of the glass.

• Internal shading devices should not block the natural ventilation.

• Limit the glare resulting from solar radiation.

• Usually the adjustable and allow occupants to regulate the amount of direct light entering their space.

2. External shading device

Overhangs, vertical fins are examples of external shading devices. They can also reduce the amount of solar heat energy passing through a window. (Fig. 1.25 (b)) de lan

They can be used to reduce the area of the glass surface i.e, actually impacted by the sun rays.ban

Shading can also be provided by natural landscaping or by building elements such as awnings, overhangs, and trellises.

The design of effective shading devices will depend on the solar orientation of a particular building facade.

For example, simple fixed overhangs are very effective at shading south-facing windows in the summer when sun angles are high.

However, the same horizontal device is ineffective at blocking low afternoon sun from entering west-facing windows during the summer.

Exterior shading devices are particularly effective in conjunction with clear glass facades. Now, a high-performance glazings are available that have very low shading coefficients (SC).

• Most thermally efficient as it controls the amount of radiation entering the building externally.

• Horizontal, Vertical or egg-crate devices

• Vegetation and other buildings can also act as shading devices.

There are three types of sun-shading devices. (Fig. 1.26) They are:

• Vertical devices

• Horizontal devices

• Egg-crate devices

Vertical Swing Devices: Vertical shading of pilasters, louvre blades or projecting fins in 45" a vertical position. Their performance is measured by the horizontal shadow %.

Horizontal Swing Devices: Horizontal shading devices are usually in the form of canopies, long verandas, movable horizontal louvre blades or roof over-hangs. They are best suited to southern and northern elevations and their performance is measured by the vertical shadow angle

Egg-crate Devices: Egg-crate devices are combinations of vertical and horizontal devices. They are usually in the form of grill blocks or decorative screens. The performance is determined by both the horizontal and vertical shadow angles.

Designing shading device

The following factors to be considered while designing any shading device.

2. Select shading type

• Horizontal

• Vertical

• Egg crate

3. Identify category

• Fixed

• Adjustable

4. Calculate design dimensions

• Understand horizontal and vertical shadow angles.