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a report by

R i c h a rd F o r s t e r

Lighting Consultant and Editor, Society of Light and Lighting Newsletter

I n t r odu c t i o n

Any hospital complex encompasses a broad range

of functional elements and is almost a self-

supporting community. The occupancy is both

complex and dynamic and, therefore, any lighting

has to meet the separate, and even conflicting,visual needs of staff, patients and visitors.

Furthermore, many areas are in use 24 hours a day,

seven days per week. Extending the natural

working day is possible by electric lighting, but for

hospitals the use of artificial lighting occurs to a

much greater extent than in normal commercial

and industrial premises.

Recommended illuminations vary from one lux for

night-lighting to 100,000 lux in operating theatres.

The first objective is the provision of adequate

illumination. Attempts to save energy by under-lighting are a false economy, as without sufficient

light errors and mistakes increase and visual fatigue

reduces the rate of work.

It is impossible to deal with all the lighting issues in

a single article, so a small number of aspects have

been selected. Their relative importance will vary

from site-to-site, but hopefully it will be possible to

audit local conditions either by a walk-through

survey or by asking a few key questions of facilities

management and procurement.

Day l i g h t

This is a good starting point and immediately

recognisable. Daylighting is an important element in

building design, as it provides variety, a link with the

outside world and a temporal scale. These aspects are

particularly important for visitors and patients who

are in an unfamiliar environment. Well-designed

daylighting of a space can reduce the reliance on

electric lighting, thus saving electricity. The

inconsistency of natural light, however, often results

in electric lighting being left switched on when it isnot needed. In fairness to the occupants of a space

there is no clear indication of the relative

contribution from electric light and daylight by

which a decision can be made to switch off electric

lighting. The potential for daylighting to save energy

is thus rarely realised.

L i gh t i n g Con t ro l s

There are various options available for the automated

control of lighting based on presence detection,photo-sensors that can measure the amount of

natural light, timers and building management

systems. Which is deemed to be the most suitable

will depend on the type of location and its usage

pattern. There are two basic rules in providing

automated switching. Firstly, there should always be

safety of movement so occupants are never deprived

of all lighting in a space and secondly there should

always be a convenient local manual override so that

the function of a space can continue.

Lighting controls are called for in Part L of theBuilding Regulations for England and Wales, either

automated or by local manual switching. For the

latter, it is important that the switching circuitry

relates to a sensible sub-division of the space. Large

open spaces can be reorganised and it is important

that the switching is changed to match the current

arrangement. Manual switching does not have to be

hard-wired and where change is likely switching by

infrared handsets, similar to the domestic TV remote

control, can be considered. Other options include

switching via telephones or PCs.

Sudden abrupt changes in lighting levels can be

disturbing and even construed as a fault condition, so

dimming is becoming more popular. With modern

light sources, such as fluorescent tubes, the

relationship between light output and power

consumed is almost linear dimming saves electricity

consumption. With filament lamps, however, the

light output decreases much more rapidly than the

power consumption, so the potential for energy

saving is less significant. Simple resistive dimmers do

not save energy but merely transfer consumption

from the lamp to the dimmer itself.

Grea t e s t Co s t

It is not normally appreciated that the greatest cost

Ef f i c ient hospi ta l l ight ing

B U S I N E S S B R I E F I N G : H O S P I T A L E N G I N E E R I N G & F A C I L I T I E S M A N A G E M E N T 2 0 0 5

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Technology & Services

Richard Forster worked for Atlas

Lighting from 1957 to 1961, as

commercial trainee, Lighting

Engineer and Senior Lighting

Engineer. He then worked as

Lighting Designer for Isora

Integrated Ceilings in 1969 and

won the Illuminating Engineering

Society (IES) National Floodlighting

competition for Coventry Cathedral

in 1972. From 1972 to 1991 Mr

Forster worked for Thorn Benham

Environmental Engineering and in

1974 as Marketing Manager for

Thorn Lighting. He was an

Independent Lighting Consultant in1991, specialising in light sources,

providing technical articles,

education and industrial training.

From 1993 to 2000 Mr Forster was

Editor of the Chartered Institution

of Building Services Engineers

(CIBSE) Lighting Division Newsletter

and was also Editor of the Society

of Light and Lighting Newsletter in

2000. He has also written various

technical articles in Building

Services Journal, Light Magazine

and other lighting trade journals as

well as papers given to IES and

CIBSE National Lighting Conferences.

Mr Forster has a City and Guild

Full Technological Certificate in

Illuminating Engineering, is a

Diploma Member of the IES and is

a Member Institution of Lighting

Engineers. He also has a lighting

diploma from the CIBSE.


2/4B U S I N E S S B R I E F I N G : H O S P I T A L E N G I N E E R I N G & F A C I L I T I E S M A N A G E M E N T 2 0 0 5

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Technology & Services

associated with lighting is the energy consumed.

Typical through-life costs are shown in Figure 1.

Changing from a normal nine-to-five, five-day

week, to 12 hours per day every day doubles the

hours of use and thus the energy consumed. For

many situations in a hospital complex this may be a

conservative estimate. Energy costs are currently

predicted to rise after a period of stable, and even

falling, prices. This is partially due to market forces,but concern about global warming and increasing

environmental pollution is applying additional

pressure to reduce energy consumption. It is,

therefore, important that hospital lighting is based on

only the most efficient light sources.

F l u o r e s c en t T ube L i g h t i n g

Probably the most common lamp in use today is the

fluorescent tube. Developed just before WWII, its

availability was restricted during the years of the

conflict and became part of the post-war buildingprogramme. Significant technical progress was made

in the 1950s with the introduction of improved

phosphor coatings generically called halophos-

phates. There were two groups of white lamps for

general lighting called white, warm white and cool

white. Better colour rendering was possible if

required, but only with approximately two-thirds of

the light output. This group was given names such as

Natural and Northlight. With this choice, good

colour rendering was restricted to situations where it

was important, such as retail premises and industrial

colour matching.

In the 1970s, new phosphors were introduced that

created white light by the addition of red, green and

blue colours and became known as triphosphors.

These had three main advantages:

increased light output typically +10% initially,

35% at end of life;

good colour rendering no longer was itnecessary to compromise efficiency for colour

rendering or vice versa. Colour rendering is

explained in more detail below;

good lumen maintenance (see Figure 2); and

longer life.

This extra performance carried a cost penalty with

triphosphor lamps at approximately twice that of their

halophosphate versions. The construction industry

has been traditionally structured so that through-lifecost benefits are not properly recognised. The

installing contractor is only interested in initial costs

and not operating costs. The purchasing department

compares component costs and favours low-cost

replacement lamps. Facilities management can

identify energy consumption, but have little

opportunity to influence equipment specification.

Higher lamp costs can be easily justified (see Figure

1). More light emitted means less luminaires to

purchase, fewer lighting points to install, lower

installed load and less equipment to maintain.

The better durability of triphosphors results in the

light output being maintained at a higher level for a

longer period.

The reduction in light output with time from the

triphosphor lamp is only approximately 5%, which is

not readily detectable by the naked eye.

Consequently, if one lamp fails its replacement will

not appear at different brightness.

With halophosphate lamps there is a much greaterfall-off in light output, which, after 9,000 hours, is

approximately 20%. A single replacement lamp

would be 25% brighter and would be apparent. This

is why the curve for the halophosphate lamp is only

Figure 1: Typical Through-life Costs. Fluorescent Luminaire Over 10 Years

Figure 2: Typical Luminous Performance Comparison


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