Daylighting for Sustainable Design

Outline

Basic Principles of Effective Daylight Design

Introduction

Conclusion

References

Daylighting: Source of heating and lighting. Daylight enters a building via four primary mechanisms;

Direct sunlight - Clear sky - Clouds (diffuse light) - Reflections from ground and nearby objects.

Daylight elements such as good lighting, window size and view out have a pivotal role in emotional satisfaction (Hourani and Hammad, 2012).

Crucial factor in determining sustainable architectural design and give a sense of pleasure in the architectural spaces.

Figure 1

The Basic Principles of Effective Daylight Design

1. Site Orientation: The orientation of buildings is important, if the length of the

building is oriented in an east-west axis, it will allow penetration of passive heating or cooling within the building on a seasonal basis (Guzowski, 2000).

A north-south facade is better as it allows penetrating a good daylight by avoiding glare and overheating.

Designers could define which rooms need direct or indirect sunlight and require the quantity of heat or heat loss.

2.Form of Building:

Identifies the quality of daylight.

Different shapes, thin linear, L- shape, U-shape and doughnut need enough natural light through the courtyard and thin building

Courtyard and thin building, increase the nature light and heat distribution to the sides of building.

Figure 2

3. Glazing Ratio: Glazing provides natural daylight but also allows

unwanted summer solar gains and winter heat losses.

The larger the windows the more daylight and solar gain will enter - but the larger the heat losses will be.

Recommended glazing ratios are generally between 25-50% of the external wall of the daylight space (Duxbury, 2013).

The optimum glazing ratio may vary due to individual factors such as orientation, location, obstructions (View of sky) and activity/user requirements.

4 Glazing Specification:

The type of glazing has a direct influence on thermal performance and daylight levels.

Triple glazing gives greater thermal comfort because its internal temperature is closer to the internal air conditions.

Triple glazing, tinted or reflective glass can result in reduced daylight levels.

Window specifications

Daylight transmission

Solar transmission = direct heat from the sun

Single glazing 88% 83%

Double glazing 77-80% 65-70%

Double glazing - tinted 29% 39%

Triple glazing 70% 40-60%

Table1 shows Window Specification and Light Transmittance

5 Window Height and Location: Windows should be high on the wall, widely distributed

and of an optimum area to achieve adequate daylighting.

Figure 4: show Light and shadow distribution produced by different windows positions, directions and sizes in a room.

Figure 3

6 Options for Overhead Daylighting:

Horizontal rooflights admit more daylight per square metre of glazed area than do vertical windows, a horizontal rooflight is proportionately three times more effective as a source of daylight than a vertical window.

Roof Lighting:

Skylights: Skylights are domed, horizontal or slightly

sloping glazed openings in the roof.Figure 5

Roof light areas should be limited to a maximum of 12% of the floor area to reduce excessive heat losses and gains.

Monitor Lighting Monitor lighting can be used to reduce glare, heat gains,

and protect internal spaces from direct sunlight, by providing an opaque roof and overhang above the glazing.

Saw Tooth Lighting Heat gains can be reduced by tilting

roof lights towards the North in order to utilise diffuse north lighting.

Figure 6

Figure 7

Clerestory Windows Clerestory windows are usually situated at a high level

(near the ceiling of the room) - always above eye level. They provide an effective source of natural light and

ventilation whilst reducing glare.

Figure 8

Conclusion In architectural design, natural daylight is a crucial

component in determining sustainable building and the quality of an indoor environment.

Many significant factors determine the quality and quantity of daylight; site orientation, form of building and type, size, location of the glazing space.

The successful design of healthy building is controlling the

natural lighting and distribute in spaces according to their needs.

Using appropriate glazing specification for buildings can result in reduce daylight levels and decrease in energy use for artificial lighting.

DUXBURY, Liane (2013). Daylight and Modeling Case Studies (2013)

GUZOWSKI, Mary. (2000). Daylighting for sustainable design. New York, McGraw-Hill.

HOURANI, May, and HAMMAD, Rizeq (2012). Impact of daylight quality on architectural space dynamics: Case study: City Mall--Amman, Jordan. Renewable and Sustainable Energy Reviews, 16 (6), 3579-3585.

LECHNE, Norbert. (2009). Heating, cooling, lighting: sustainable design methods for architects. 3rd ed., Canada, John Wiley, Hoboken and NJ.

PHILLIPS, Derek. (2004). Daylighting: natural light in architecture . Oxford, Architectural Press.

SMITH, Peter F. (2005). Architecture in a climate of change: A guide to sustainable design. 2nd ed., Oxford, Architectural Press. 

YAO, J. and ZHU, N. (2012). Evaluation of indoor thermal environmental, energy and daylighting performance of thermotropic windows. [online]. Building and Environment, 49, 283-29. Article from Science Direct last accessed 21 August 2013 at: http://www.sciencedirect.c.

References

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