Tubular Daylight Guidance

Systems: building codes and the environment

Mohammed Al-Marwaee and David CarterSchool of ArchitectureUniversity of Liverpool

Daylight guidance systems (DGS) Tubular guidance systems redirect daylight into areas of buildings that cannot be lit by conventional glazing.

Tubular daylight guidance technology

1. Active collectors

These track the movement of the sun using mirrors and lenses (heliostats), but incur a high capital and control cost.

2. Passive collectors

These are essentially vertical tubes capped by a light collector, and are commonly used for task and amenity lighting.

Passive zenithal

Passive zenithal collector

Light guides

Guides made of aluminium sheet coated with either silver (95% RF) of multilayer plastic (99% RF)

Straights and bends available

Passive zenithal emitter

Passive zenithal emitter (2)

Fits 600mm ceiling module

Building codes regulation

• Structural stabilityStability and integrity under wind & dead loads

• Fire protectionTo prevent fire spread over surfaces, fire and smoke spread within and between buildings, and ensure fire separation within and between adjoining buildings

• Materials durability and weatherproofing

Ensure durability of materials in long term use. Stability of materials under prevailing climatic conditions

• Thermal considerationsTo conserve energy by minimising heat loss and gain

• Lighting issuesMost regulations refer to electric lighting but most Codes encourage the use of daylight

Building codes - Structural stability• Few structural implications for TDGS • Heliostats require additional structural work to account for

wind and dead loads • Transport elements have small dead load but must not

conflict with structural beams etc

Building codes - Fire protection• Regulations for fire protection are based on similar principles

worldwide• Prevent and fire and smoke spread within buildings using fire

compartments• Prevent fire spread over surfaces by using non -combustible

materials • Fire separation between adjoining buildings

Fire and smoke within buildings and TDGS

• Both vertical and horizontal transport components of TDGS may pass through compartment enclosures

• Fire protected ducts or cladding used for vertical routing through compartments in multi-storey buildings

• TDGS must be fire-stopped whenever they penetrate fire-resisting walls, floors and ceilings using fire dampers

Fire and smoke between buildings and TDGS

• Spread of fire between buildings is controlled by limiting the area of unprotected building envelope glazing aperture

• The optical efficiency of TDGS compared with conventional roof lights can have a beneficial effect of limiting unprotected roof aperture

• TDGS present no greater risk of internal surface spread of flame than electric lighting luminaires being made of similar materials

• Majority of TDGS are in single storey buildings - that is into one compartment and most codes allow penetration of the building envelope alone

Lighting and TDGS

• TDGS can be used to provide daylight into areas of buildings far from the building envelope

• TDGS are capable of delivering useful quantities of daylight dependant on the configuration of the interior and the lighting system and its controls – up to 2% Daylight Factor

• There is a need for daylight linked electric lighting to permit substitution by daylight

The environment and ‘climate change’

• ‘Climate change’ is a major crisis facing mankind• Attempts to address the problem have concentrated on

reduction of greenhouse gases, notably CO2, by reducing emissions

• The largest consumers of energy in most countries are within the building stock

• Daylight can reduce the environmental impact of lighting by acting as a Lighting is a major consumer of energy

• substitute for electric light • Daylight is more efficient than electric light, its efficacy being

of the order of ten times more than that of an incandescent lamp and therefore can lower the cooling requirements of a building

Building Codes and CO2

• Energy usage and CO2 emission is the main criteria for satisfying the energy-related parts of European Building Codes

• Assessment is carried out using software from input of a description of the building geometry, construction, use and HVAC and lighting equipment

• The provision or otherwise of daylight within a building is a major part of the assessment procedure

• Work by the authors suggests that buildings that would not otherwise gain Building Code approval would do so with the addition of light guides

Case studies of installations

1- University building

•Top floor of existing three storey

building.

•Penetrates roof only

•Small unprotected roof area

•Provides insufficient daylight for tasks

•Electric lighting not daylight linked

•Daylight linked TDGS reduces the

annual CO2 emissions by 20.7 mT.

(85 %).

2- Office•Two storey office

•12m guides in roof space require support

•Conflict with other services in roof

•Guides not fire protected

•Makes substantial contribution to task

illuminance

•TDGS will, assuming daylight linking, reduce

annual CO2 emissions by 1.2 mT. (41 %).

3- School

•Purpose built two storey

•Guides to upper floor penetrate only roof

•Guides to lower floor in brick vertical duct

•Not enough guides to provide sufficient task illuminance

•TDGS will, assuming daylight linking, reduce annual CO2

emissions by 1.1 mT. (61 %).

4 - Villa Fida•Three-storey villa in Riyadh, Saudi Arabia

•.Most of the guides installed in the basement

•Collectors in garden rather than the roof and integrated

into landscape and at night the guides transport internal

lighting to the garden

•TDGS will, assuming daylight linking, reduce annual CO2

emissions by 1.1 mT. (41 %)

4600sqm warehouse lit using 105No 650mm dia guides

A daylit cave!

Conclusions

• Codes do not specifically refer to TDGS.

• Codes treat collectors as rooflights, transport elements as pipes or ducts, and emitters as luminaires.

• Still need for new products- eg. Low optical loss for protection at compartment walls and prefabricated fire resistant cladding.

• The technical development of system components has arguably outstripped consideration of practical issues of detailing and buildability.