Lighting Effects in Architecture - Deltalight (UK) Ltd
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Welcome to the Deltalight's online CPD seminar, titled the lighting effects in architecture. Deltalight are a Belgian based lighting company established in 1992, the UK division was established in 1997. The UK has two bases: a design studio in London Waterloo that houses a team of qualified individuals to give lighting solutions and technical assistance. The second office is in Hazelmere and focuses on logistics.
Deltalight's global head office is based in Kortrijk Belgium the impressive 26,000 square meter site looks at research and development, manufacturing and hosts a showroom and lighting laboratory. All the fittings are thoroughly tested in our laboratories to ensure that they comply with the relevant European standards.
In the UK one of the services we offer is a free lighting design service. We can produce 3D images based on the measured photometric data of the light fixture. This enables the client to see a visual representation of the lighting in the spaces before the project commences.
Aims and Objectives
The aim of this CPD is to give a basic understanding of lighting principles, terms, light output and colour so the importance of a lighting design is understood and becomes an integrated part of the building architecture.
So, what is light?
Light is magnetic radiation the human eye can see only a small portion of the radiation admitted between 380 and 700 nanometres. The eye is most sensitive around 555 nanometres. This is towards the warm yellow green part of the spectrum.
So, if the eye is sensitive in this part of the spectrum in theory, we should see more light from a warm colour temperature lamp than a cold temperature. To prove this next time, you're outside when it's dark look at car number plates and the road lighting, usually yellow. Today the common term we hear for seeing light is lux, but we do not see lux.
Flow and Intensity of Light
If we look at the common lamp types available, most of them are based on the basic technology of heating a wire to make it glow as Edison and Swan concluded, but new materials do things more efficiently.
If we look at the low voltage tungsten halogen lamp I expect you may have used one due to the small size and quality of light. But, is it efficient?
Because we use a 12 Volt the filament can be very small but it can be heated up to a high temperature due to the quartz envelope and also the reflector is glass with the dichroic coating. This allows the infrared light and the heat to pass back through the reflector to give a cool white beam, ideal for display lighting. The units we measure out are in lumens. Lux is the number of lumens falling in a square metre, i.e. 500 Lux is 500 lumens per square meter.
The level of efficiency is based on how much energy you're burning in watts in proportion to the amount of light based then shows in units of lumens per watt. We can see the efficiency on the screen but for design purposes we must look at other characteristics of the lamp, such as colour and light quality and distribution. Watts is the power consumed so it's necessary to balance power consumption with the quality of light combined with the lighting effects.
Building regulations Part L - Energy Efficiency in Lighting
Building regulations part L includes lighting in its recommendation for power consumption. It recommends that for commercial areas we should have at least 45 lumens per watt and display lighting 15 lumens per watt. So, for most areas we can use a mixture of low voltage tungsten and fluorescent.
This installation shows the ambient light being created by the fluorescent lights and the interest in the space by the low voltage narrow beams.
Fluorescent lights don't have to be linear due to the development of compact fluorescent lamps as shown and, again we use low voltage lamps to give the lighting interest.
LEDs - Light Emitting Diodes
We have not yet talked about LEDs, light emitting diodes, in terms of lumen output and energy saving as there are many different types and quality of LED, but as a general rule an LED gives about 40 lumens per watt. Most LEDs are one or three watts, it would not be cost effective to light a space to a general lighting level.
The main advantage is the long life of 30,000 to 40,000 hours and the LED is cold temperature, so they are safe to use in areas where the fixture can be touched. The development of LEDs is continuing, and the lumen output will increase in time.
Manufacturers create reflectors to work with the lamps, to get various beam distributions.
This installation shows the use of narrow beams creating a dramatic effect with high contrasts. This would make it difficult to perform everyday office tasks and would give the individual eye strain and headaches, as the eye is constantly adapting to suit the large difference in contrasting light levels.
However, if this is a showroom the focused pools of light bring the product to the observer’s attention.
Alternatively, the use of wide beams creates a high uniform lighting level but, with very little interest. Is this what the client wants? is it the right quality of light for residential? As detailed the designer has incorporated narrow beams to give a more visually pleasing effect.
How do we know how much light is emitted from a lighting fixture?
This is measured in candelas the amount of light in a solid angle. Luminance candelas is what we see. This is the light reflected off a service to prove this, if I shine a light at a white object on a black background, we will see the object as we see the reflected light towards our eye. If it were black, we would not see it as black reflects no light. This is why it's important that the wall, ceiling and floor reflectance values are known before starting a lighting design.
Road lighting design is all based on luminance from the road surface to the eye of an observer in a car.
Let's look at this narrow beam.
This diagram looks confusing but is very simple.
There is a picture of the product and the data shows the wattage and lumen output. However, the diagram shown in blue details of the type and intensity of the light distribution.
The Deltalight lighting laboratory may use the light distribution in candelas using an instrument called goniophotometer on the vertical and azimuth planes to create the cone shape.
If you imagine the centre of the diagram is the light fixture and the point directly under it is the peak intensity, a down lighter in the ceiling shines straight down. You walk into the room from a door on the right hand side and walked the 30 degree point, look up towards the light the light coming towards your eye would be very little, in the order of 100 candelas. But, as you walk towards the fixture but like becomes more intense, until you're standing directly under it and looking up directly into the main beam. This tells us that the fixture has a strong narrow beam of 23 degrees with a peak intensity of 6000 candelas.
Lux Levels for Lighting Design
But for design purposes, we need to know the Lux level as this is the easiest way to calculate and measure light, so manufacturers create cone diagrams that give the Lux level and the beam distribution. The cone indicated shows at 2 meters from the size of the main beam is 0.82 meters and the Lux level is 2,096.
If we look how this information can be used the correct product is used to create the desired lighting effect. If your client gives you a brief that he wants to create an interesting lighting effect, so the restaurant looks stylish and inviting in the busy times, he wants a quick turn round in custom and in the evenings, he wants the customer to stay longer and spend more money. Lighting is one of the key factors that can help create the correct environment.
In this installation a narrow beam fixture has been selected to give strong pools of light on the tables. As shown in the previous slides we can see that the beam would have a diameter of 0.82 meters and a Lux level of 2,096. The space would have a good visual effect of high interest, but the customer would soon feel uncomfortable with the harsh contrasts which are the requirement during the busy times.
But what about in the evenings? the installation could be dimmed to give a low lighting level, so the customer feels relaxed and comfortable resulting in them staying longer.
The previous fixture had a symmetrical beam, in this instance the fixture has a different beam distribution and the axle and transverse planes.
As you can see the diagram now shows the two distributions on the two planes, and as previously this can be transposed into Lux levels at various distances from the light fixture. This installation is in a public restaurant in Buckingham Palace which shows the energy saving compact fluorescent fixture used, in conjunction with the symmetrical low voltage units to create a high level of ambient light, but with the key features brought to life.
Note the use of cold cathode lighting used around the central gondola to give a floating effect.
All the diagrams shown up to now have only had light in the downward hemisphere but of course we can have light in the upward hemisphere to give indirect light.
Lighting Guide 7 (LG7)
By having light in the upper hemisphere the criteria for office lighting can be achieved, the old system was called lighting guide 3 LG3 with the fixture complying with set beam distributions namely Category 1 2 or 3 LG3 cat 2.
The new recommendation for office lighting is called lighting guides 7 LG7, which now asks for the walls and the ceilings to achieve a certain lighting level which is a percentage of the light on the working plan.
These recommendations are achieved after extensive research by the Society of Light and Lighting and the Chartered Institute of Building Service Engineers. This installation gives direct or indirect light, so not only is the working plane lit but the walls and ceiling are bright which gives a more vibrant space to work in.
It must be noted the LG7 is the complete design requirement for the space and it is not the individual fixture that complies, it is the design. This slide indicates that if the fixture is mounted too close to the ceiling the design would not comply, as the ceiling is not uniform.
Cost is always an issue so consider using a product that combines different lights together so, only one installation point is required. In this instance the one fixture replaces 3.
This installation shows the flexibility on combined units using dimmers or switches to control the lighting, so energy can be saved, and the lighting effect can be changed depending on the image required for the product on display.
How do we Know How Much Light we need to Design to?
The CIBC lighting guide gives us the information, but we must remember to look at the lighting effect and not just the level or the architecture will not have the required result.
Surface reflectance is an important note, we do not see luminance Lux, we see luminance the reflected light.
Today the lighting computer programs can be linked with AutoCAD, so we can provide simulations of the light effect. In this instance we've used a program called Relux that works from measured photometric data, which enables us to get accurate results.
If we look at a typical meeting room with a centreboard table fluorescent fixtures give indirect light and low voltage downlights are around the perimeter.
We switched the lights on, and the visual appearance looks good with a good uniform light over the desk and pattern effect on the walls.
If the walls are black the appearance is totally different however the lighting level on the working plane is only reduced by 10% as most of the light is reflected light from the ceiling.
This is the effect with black walls and ceiling, 90% of the reflected light is absorbed by the ceiling. We still have the same amount of lumens with energy efficient fluorescent lamps, but because of the design we have negligible working light.
If we look at the horizontal lighting levels with the white walls and ceiling in place, we can see that the levels over the desk of 500 Lux with a good uniformity. We can also see but the surfaces have to be taken into account with the lighting solution to suit.
What about vertical planes?
Here the computer generated visual looks good. But from the calculated lighting levels we can see a hotspot in the centre of each picture, this can be overcome using lenses to spread the light again, the surface reflection is important.
The pictures on the far right side shows they have a specular reflectance and therefore it reflects the lamp directly to the observer therefore the angle of viewing needs to be changed and the fixture needs a lens to give a soft beam.
What Lux level do we need and how can we visualise it?
This is a 50 Lux.
This shows a typical arrangement for exterior lighting, so the lighting is adequate for movement and safety. But let's think in another dimension when the lighting is mounted into the ground to light the building and show its sharp features. The reflected light Ben lights the pedestrian walkway.
100 to 200 Lux.
A corridor does not have to have the standard arrangement of lights in the centre of the ceiling evenly spaced; the lighting can be random to suit the building design and architecture. Here's another corridor with a different approach; note that there are three beams of light from one fixture; the narrow beams have a dramatic effect to complement the space. A heritage building uses a simple continuous lighting system with a wide, indirect beam to give a glare free uniform view of the featured ceiling.
Areas that require 300 Lux. Domestic bathroom. In a room such as a bathroom there are many different materials and services such as ceramics, glass, marble, wood etc. Therefore it's important to bring them to life. Fluorescent lighting can make the space look flat and lifeless, so low voltage is used to bring some sparkle and life to the room.
Areas that require 200 to 400 Lux.
General working areas such as receptions need two treatments, but general lighting levels need to be achieved and the appearance also needs to give the correct image for the company profile. In this instance the area has dark walls, so reflections are minimal, and the space feels very claustrophobic. To remedy this the designer has used a full Sky effect with fluorescent lamps behind an opaque material. The use of strong narrow beams of light creates interest.
This company wants to portray a fun image, so the fixtures are randomly installed but the Lux lighting level is the same.
Domestic areas need special treatment as there are different tasks happening at different times of the day, for example when the family comes home from work or school the lighting may need to be at a higher level but, as the evening goes on the lighting requirement is less, so switching or dimming may be required. A college or school must maintain the lighting level.
This project is the Bank of England and shows the difference between the lighting effect using the old LG3 lighting system as shown on the right hand side, and the new LG7 on the left, where the walls and ceilings are led to a higher level to give a more pleasing work environment.
To reiterate the units to take into consideration:
- Lumens: the power of the lamp,
- Candela's: the intensity from the fixture,
- Lux: the light falling onto the area, the number of lumens in a square metre,
- Candela's: the intensity of light reflected off the surface, this is what we see.
There are two main factors to take into account, colour appearance and colour rendering. If you look at a poorly maintained office, you will probably see lamps that look different colours. This is because although they are the same wattage, the colour temperature is different. One cold, looks white and the other warm, looks more yellow.
The criteria in choosing, which is the correct lamp colour for the project is difficult. A warm lamp makes the objects colour appear more vibrant, especially the reds. With a cold colour temperature the Blues are more prominent. You can experience this effect in a supermarket where different colour temperature lamps are used to enhance the colour of the products, i.e. cold for the fish counter and warm colour temperature for the bakery.
The chromaticity diagram shows the colours achieved at different temperatures. The effects of different colour temperatures as shown in this slide. All lamps have a colour rendering index, an RA, which is the ability to distinguish colours under the light emitted.
For example, if you use a low pressure sodium lamp for road lighting you would not be able to distinguish the different colours of objects, as they would appear different shades of grey. Each lamp is given an RA index, an exterior lamp with an RA index of 80 or more should be used.
This indicates the use of sodium lighting with an RA index of 20 for the road lighting and, a metal halide lamp with NRA index of 80 to light the building, so the concrete shows its true colour and texture.
The next two slides show an overview of the popular lamp types, showing their characteristics. The basic rule of dimming is that the tungsten low voltage and fluorescent lighting can be dimmed as long as they are supplied with the correct components, but metal halide cannot.
These two slides give you a useful checklist to run through when choosing a lighting fix to ensure all aspects of the design criteria are taken into account.
We trust the aims and objectives have been met. Do not hesitate to contact Deltalight if you have any questions.