Lighting can make or break a room. Get it right and the décor and furniture will blend to create the perfect atmosphere and/or working environment.
How much light do I need?
Step 1 – Room Area:
The first step in deciding what lights to put in a room is to calculate its area. For example if your room is 4 metres by 5 metres then its area is 4 x 5, which is 20 sq metres. You can follow the same process for Feet/Inches.
Step 2 – Lumens:
Next you want to know the number of Lumens (scroll down to read about different terms used to describe lighting) you will need. Lumens are a more accurate/modern way of calculating light levels than Wattage and allow us to compare all the different types of lamp. The more lumens a lamp has the brighter it will be. The number of Lumens you will need will also be influenced by the purpose of the room and how it is decorated – dark rooms will need more lumens than light ones. If you google “how much light do I need?” you’ll get a variety of different figures ranging from 100 for simple approximation to 700-800 for a task but a basic rule of thumb is:
- Floors: 215 Lumens per Square Metre
- Tables and Raised Surfaces: 323 Lumens per Square Metre
- Desks and Task Lighting: 538 Lumens per Square Metre.
If you are changing the lighting in a room it might be worth deciding whether you want to increase or reduce the amount of light you have. There are a variety of different light level apps avaiable for smart phones – although I would only trust them to give an approximate value. You might also consider whether you like to split the lighting into sections or introduce a dimmer so you can adjust light levels depending to create different moods. The table below shows some other suggested values or for a different calculation you could try the Chalston Lights Light Calculator.
What Colour should I go for?
The following image from http://www.westinghouselighting shows how different light colours can affect the mood and where different colours work best.
Down Lights are increasing popular as a form of lighting in houses and for understandable reasons. Its possible to create a spread of light across a room targeting specific areas and on a multiple way system you can create moods throughout a room.
If we know the area of a room we can use 1 down light per 1.2 square metres to give us an approximate number of units required. We can fine tune this considering: room purpose; shape of the room; height of ceiling; and decoration.
Down Lights shouldn’t be placed in the corners of a room. They should be positioned 600 to 750mm from the walls. The distance between them should be around half the height of the ceiling but this can be adjusted to match the shape of the room. By picking units with suitable beam angles that match the room dimensions and purpose you can keep shadows to a minimum. Scotlightdirect have a good explanation of the dos and donots on their website.
A reminder on some of the terms used in lighting.
A lumen is defined as the total amount of visible light given by a lamp in any particular direction. It has the symbol lm. Well that’s a nice and simple way to define it. Wikipedia gives one that is more exact!
Lux is a metric measure of how much light there is over a given surface area and can be described as illuminance. One Lux is equal to one Lumen per square meter.
Footcandle is an imperial measure of illuminance for when you have measurements in feet/inches. One Footcandle (fc) is equal to one lumen per square foot.
Power is rate at which energy is used so Watts (the unit of power) is describes the amount of energy used over time. In simple terms the more watts a lamp has the more electricity is will use and therefore the more money it will cost to run.