SOME IMPORTANT CONSIDERATIONS FOR LOW ENERGY LIGHTING by Bill Noble (lighting designer)
There are several good reasons to think low energy when choosing light fittings and lamps, not least because the building regulations tell us we have to! But being forced to use low energy lamps is no bad thing because it is, in the long term, good for our pockets as well. Low energy lamps save on running costs with lower electricity bills and lower maintenance costs (with low energy lamps lasting anywhere between 10 and 50 times as long as traditional filament lamps).
LED OR FLUORESCENT?
When choosing low energy lamps the first thing to consider is LED or fluorescent? Compact fluorescent lamps can have disadvantages in a domestic environment so you should always, budget permitting, prefer LEDs to fluorescents. Disadvantages of fluorescents in domestic environments include:
They take a long time to warm up to full brightness (even longer in colder rooms)
Most are not dimmable
They must be disposed of carefully (because of the toxic materials they contain they cannot simply be thrown away)
Some people are adversely affected by the EMF radiation emitted by fluorescent lamps
They have shorter lives compared to LEDs
Fortunately most fluorescent lamps now have LED versions.
THINGS TO CONSIDER WHEN CHOOSING LED LAMPS
When choosing LED lamps there are a number of things you need to consider to ensure you get something that is suitable for your needs.
Colour temperature - To get a colour of light similar in warmth to a filament lamp you will need a colour temperature of 2700K. Many LED lamps have a colour temperature of 3000K or more and will appear colder, perhaps even bluer, in colour. The larger the number the colder the light. Daylight has a colour temperature of around 5500K.
Colour rendering (CRI) -This is a measure of how accurately a lamp will render the colour of an object. Filament lamps have a colour rendering index of 100%. If the lamp is to be used in a location where the true colour of objects is important (for example when lighting pictures) then you should choose as high a CRI as possible. LED lamps typically have CRIs of between 70 and 90.
Light output - If you are replacing a filament lamp with an LED alternative, or you are just wanting something of a similar brightness, you need to take note of the light output of the LED lamp. Unfortunately you cannot simply rely on the manufacturer's statement that their lamp is equivalent to an x watt filament lamp as some manufacturers use misleading ways to calculate this. What is really of interest is the total amount of light emitted by the lamp, but some manufacturers instead compare the light hitting a section of the horizontal plane immediately beneath the lamp. If possible find the lumen output of the filament lamp being replaced and compare it with the lumen output of the LED lamp. Warning…just because a manufacturer says their GU10 LED is equivalent to a 50W traditional GU10 lamp it does not necessarily mean that it produces the same amount of light! It may just mean that there is the same amount of light underneath the lamp but not, perhaps, around the edge.
Dimming - Compatibility of dimmable LED lamps with dimmer switches is currently a nightmare. It varies hugely from manufacturer to manufacturer. The only way to be sure is to check with the manufacturer of the LED lamp that the particular dimmer switch you want to use is compatible.
By and large you get what you pay for with LED lamps. The more expensive lamps generally have a better combination of colour temperature and light output.
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