Daylight lighting systems

[edit] Introduction

Government policy and legislation such as the Climate Change Act, Carbon Plan, Infrastructure Act, Building Regulations and Construction 2025 mean that the construction industry needs to find ways to reduce the energy consumption of buildings. 'Natural' daylight systems may be one way of contributing to these reductions in carbon emissions.

[edit] Daylight systems

Daylight systems collect natural light and deliver it deep into the heart of buildings. They use collectors in the roof to harvest light, then transport it to diffusers in interior spaces. The quality of this natural light tends to be alive and vibrant, and diffusers can be placed strategically to allow the best distribution of light within the interior.

There are four main types of daylighting system:

• Tubular daylight devices.
• Vertical systems.
• Horizontal systems.
• Fibre optical devices.

[edit] Tubular Daylight Devices

Also called TDDs, tubular daylight devices consist of a fixed ocular that collects light from the roof of a building and directs it into a tubular 'pipe' lined with a highly-reflective surface. The light is reflected down the tube by this surface to diffusers in the interior of the building that direct it into occupied spaces.

This system has many advantages:

• It has no mechanical parts.
• It is relatively inexpensive.
• It can harvest relatively low levels or light.
• Tubes can be as small as 10 inches in diameter, meaning they can easily be run through the walls.

Disadvantages include, the need for one ocular per tube, and a significant loss of light beyond 10 m (that is to say, it is only practical to transport light up to 3 floors), or where there is a change of direction in the tube.

[edit] Vertical Systems

Vertical systems are very similar to TDDs, but they use a powered tracking system to point a light 'collector' towards the sun, and a series of mirrors and lenses that concentrate the light before directing it into distributing tubes.

As a result, much more light can be collected, and it can be delivered 3 to 7 times deeper into the building than would be possible with TDD's. However, a 60 cm opening is required in the roof, and the system is relatively inexpensive.

[edit] Horizontal systems

Horizontal systems use lenses to collect natural light from external walls and transport it through flat light ducts above the ceiling to diffusers placed deep inside the building. They make use of a polymer material that combines a high reflectivity with the practicality of a hollow duct similar to a ventilation duct.

Horizontal systems are a fairly recent development and as such are relatively untested and expensive.

[edit] Fibre Optical

Fibre optical systems collect light with mirrors and lenses which track the sun and transport it into a buildings interior through fibre optic cables. As fibre optic cables are relatively flexible, they can be installed in a similar way to electric cables and can be 'bent' in any direction (above a minimum 50 mm radius). They also require little space, meaning they can deliver light almost anywhere in a building. Diffusers can be replaced by point lights.

However, fibre optical systems harvest predominately direct (rather than diffuse) light and tend to be expensive.

[edit] Alternative meaning

The term 'daylighting' can also refer to: 'The removal of a culvert to restore a watercourse to a more natural state.' Ref Culvert, screen and outfall manual, (CIRIA C786) published by CIRIA in 2019.

This article was created by --Jose Poyan 18:25, 1 December 2012 (UTC)

[edit] Related articles on Designing Buildings

• Automated blinds.
• BRE Expert Collection 6 Daylight and shading.
• BREEAM Visual comfort View out.
• BREEAM Visual comfort Daylighting.
• Colour Rendering Index CRI.
• Daylit space.
• General lighting v task lighting.
• Light shelf.
• Lighting.
• Lighting and offices.
• Lighting control
• Types of blinds.
• Types of lighting.
• Velux window.
• When hospital buildings aren’t healthy.

[edit] External references

• AIA: Advanced Daylighting Technologies.
• http://www.monodraught.com/
• http://www.solatube.com/