When designing a lighting system it’s essential not to lose sight of the most important issue in the space – meeting the needs of the people.John Craven of Whitecroft Lighting explains how the people factor fits into the equation.
With so much emphasis on the technicalities of a lighting design – luminance limits,glare control,room surface illuminances etc – it can be easy to forget why we install lighting in buildings.If everything was done by robots,we wouldn’t need light;we only put lighting in for the people.Yet the people factor is so often ignored when it comes to costing a project and specifying the most appropriate luminaires.
The people factor is important,whatever the application.In an office, the lighting influences the overall environment and the environment impinges on staff productivity and retention.In sectors whose sole raison d’être is people,it becomes even more important. For example,educational establishments are all about adding value to people, while the role of the health sector is to get people well as quickly as possible.
It’s interesting to make a comparison between the cost of installing good lighting and the cost of running a building.
According to the Royal Academy of Engineering,for every £1 that is spent on the construction of a building, £5 is spent on facilities
management and £200 is spent on the people working in the building during its life.
Of course,lighting only represents a small proportion of every £1
spent on constructing a building, but it is often the area for cuts
when the project starts to go over budget.Look at the lighting in the
context of people,however,and it really puts things into perspective.
For instance,if we consider a workstation served by two light fittings,the cost difference between basic modular fluorescent fittings with ‘Cat 2’ louvres and fittings that also light the ceiling and walls is about £120.
The difference in the quality of the lit environment is much greater. So too is the difference in staff morale, productivity and retention. Studies at the Rensselaer Polytechnic Institute showed that an environmentally friendly workstation achieved a three percent increase in productivity.Lighting is a significant contributor to that workstation environment.
The average cost to a company of employing an office worker is around £27,000, so an increase of just one percent in that person’s
productivity can be valued at £270.Returning to the cost comparison of lighting above,this means that spending just £120 more on better lighting will provide a payback of less than six months,assuming the increase in productivity is only one percent.
Another way of looking at this is to consider the average life of a
lighting installation,which is 10 years.If a payback of 10 years were acceptable,then it would only be necessary to achieve a 0.05 percent increase in productivity – far less than companies can realistically expect.
It’s also important to consider the cost of staff turnover. It is now
accepted that a poor quality working environment causes an increase in staff absenteeism and turnover.Lighting that creates a dreary environment with a lot of contrast between surfaces reduces morale and causes the eyes to continually adapt to the varying brightness of different areas.This in turn leads to stress,headaches and higher absenteeism.
As staff turnover increases,so do recruitment costs,training costs and administration time.There is also a fall off in productivity while new staff are being sourced and trained.
These same considerations can be applied to schools and further education establishments, where a positive learning environment is
essential. Again, the cost of the lighting is infinitesimal compared
to the cost of educating the people.In a primary school the total costs are around £2300 per annum per pupil, rising to £12,000 per annum for university students.The cost of providing quality lighting is very low in comparison;the cost of failing to provide a positive learning environment is enormous.
In hospitals, the benefits of good lighting are just as marked.
Research carried out at Sheffield University showed that a positive
ward environment could reduce patient recovery times by between 14 percent and 21 percent.There was also a marked reduction in prescription of pain killers in the two hospitals used in the trial.
Even Florence Nightingale knew that good lighting was an important factor in patient recovery and,again,the cost difference between good and bad lighting is relatively small.For example,the conventional arrangement for a four bed ward is to use downlighters in the centre of the ward with additional downlighters above each bed.A more patient-friendly approach is to combine the central downlighters with bedhead lighting that provides uplighting and downlighting.
The bedhead lighting approach provides a much brighter environment; especially for prone patients who spent a lot of time looking at the ceiling,yet the cost difference for the whole ward is only around £150.There are also fewer fittings so the cost of relamping
is also reduced.
When that £150 is equated to an increased throughput of patients of up to 21 percent,and the impact this would have on waiting lists, it’s clear that lighting needs to be viewed in perspective – with the focus on people.
Getting it right
The way to achieve good lighting in offices is laid down by CIBSE LG3:2001, but these same principles should be applied to every application that involves people.In order to do that,we have identified seven key criteria to take into account and these are listed and explained below:
• Luminance limit
• Contrast control
• Room surface illuminance
• Aesthetics
• Energy consumption
• Maintenance costs
• Installed cost
Luminance limit at required cut off angle Ensuring the right luminance limit will help to minimise screen reflections and discomfort glare and should be calculated at the precise limiting angle.If the luminance limit is too high,it will cause reflections on screens;if it is too low there will be ‘dark’holes in the ceiling.
Controlled contrast
Controlling contrast will minimise discomfort glare within the space. There is no precise measure of contrast but research has shown that maintaining a 10:1 ratio of luminance levels between adjacent areas will provide a comfortable level of contrast.
Room surface brightness
Achieving the right levels of brightness on the surfaces around the
room is the key to creating a bright and interesting environment. As
a guide,LG3 states that illuminance on the walls should be 50 percent of the illuminance on the working plane and the ceiling illuminance should be 30 percent.For ceilings lower than 2.4m,20 percent is acceptable.
A useful rule of thumb when considering surface illuminances is that in an open plan office the ceiling plane is dominant, whereas in a smaller area(less than 60m2)it will be the walls that are dominant.
Aesthetics
Aesthetics, of course, are very subjective and the best approach is
to score alternative schemes against each other, gathering opinions
from designers and end users.
Life cycle cost - energy consumption
Optimising energy consumption while delivering an effective lighting solution is now a requirement of the Building Regulations,and will be determined by the choice of lamps and control gear,the efficiency of the luminaires,the average target illuminance and the lighting control strategy.
Life cycle - maintenance
It is also necessary to minimise planned maintenance and cleaning cycles, to provide a low cost of ownership. Considerations such as lamp life and whether the design of the luminaire allows easy access for maintenance all need to be taken into account.
Installed cost
Delivering an installed cost that is within budget, is perceived as
good value and provides an effective lighting solution is a challenge
for any project.To achieve this it is important to consider the lighting needs early on in the project and to set realistic budgets.
Choosing luminaires that provide good light distribution will reduce the number of lighting points and,therefore,the installed costs. For instance,a semi-recessed luminaire that provides downlighting, wall washing and a wash of light across the ceiling will meet the visual needs of the users and will satisfy LG7-05 with far fewer lighting points than a solution using a mixture of luminaire types. This is a particularly effective solution in spaces with lower ceilings, where suspended direct/indirect luminaires are not practical.
The upshot of all this is that it isn’t really the luminaires and light sources that achieve a good lighting scheme.It is a focus on the needs of the people in the space that must come first – choosing
the right luminaires and light sources merely helps you achieve that.
