The incandescent bulb is the most common – and one of the least energy-efficient lighting options for brightening a space. Today we have numerous fluorescent type fittings; both, the old tubelight as well as modern compacts which retro-fit into incandescent holders. Light Emitting Diodes – LEDs – are rapidly getting cheaper and have now reached a level of affordability. The ways of lighting an interior or exterior space are numerous. We’ll touch on a few common ones here and see how they compare.
Apart from being free, studies have shown that natural light improves productivity and has significant health benefits compared to artificial light. Getting natural light into your home or office is not difficult to do – all it takes is a little planning by the architect at the design stage. Naturally, the designer has to take care of glare and solar heat-gain but once these factors are accounted for, there’s nothing better than sunshine to light up your life.
Unlike in Europe and North America, in peninsular India, light from the north east is the best because it is glare-free. In fact, that’s why vastu stipulates that you put your study in that very corner of your house. Conversely, the south-west is where the glare is worst so it’s better to have shade giving trees to protect you on that side. If you are living in the extreme north of our country, however, where it is really cold in winter, you’d want to open out your southern side and achieve some heat gain. For the rest of us, reflected and indirect light is the best.
The mechanics of daylighting are more complicated and will, time-willing, have a page of their own but suffice to say that every architect should try to achieve adequate lighting without building up heat inside the building.
Tubelights have been around for a while and, because of the harsh light they gave off in their early days, there are numerous people who hate their very existence. But tubelights are efficient and their colour temperature has improved dramatically in recent times which makes them as comfortable to use, if not more so, than an ordinary bulb.
Tubelights have a long life and their drawback, if any, it is that they require a lot of energy to start up. So much, in fact, that it’s better to leave a tubelight on for 15 minutes than to switch it off and on again during that time.
Compact Fluorescent Lights
CFLs are the new tubelights – they have been squeezed and twisted so that they can replace ordinary bulbs. And they should! CFLs consume just 25% of the energy that a bulb does and are available in “soft white” which is easy on the eyes. Granted, they cost more but the energy saved is more than paid back during it’s life which is 10 times as long as a bulb.
LEDs or Light Emitting Diodes are extremely energy efficient and should last for at least 10 years of continuous usage. The drawback is that LEDs are still quite expensive although rapid advances in technology and economies of scale are bringing that barrier down. An LED lamp uses, on average, about 10% of the power that an incandescent would. Add that to its longevity and we have a future winner here.
Here is a comparison that tells you approximately how much you benefit by installing fluorescent fittings in place of incandescent ones. LEDs have not yet reached mainstream sales so they have been excluded from the table. I am sure that in a short while, though, they’ll be leading the pack.
|Cost Comparison over 10,000 hrs Usage||Bulb||CFL||Tube|
|(a)||Life of single bulb/tube||(hrs)||1,000||10,000||2,000|
|(b)||Number of bulbs/tubes required||Nos.||10||1||5|
|(c)||Cost of each bulb/tube||(Rs.)||10||200||40|
|(d)||Total cost of bulbs/tubes [(b) x (c)]||(Rs.)||100||200||200|
|(e)||Light Output [lumens per watt]||(lm/W)||15||60||75|
|(f)||Power requirement [equivalent to 100W bulb]||(W)||100||25||20|
|(h)||Running Cost [@ Rs. 5/kWh]||(Rs.)||5,000||1,250||1,000|
|(i)||Overall Cost [(d) + (h)]||(Rs.)||5,100||1,450||1,200|
|(j)||Saving compared to ordinary bulb||(Rs.)||NA||3,650||3,900|
As you can see, above, the ordinary tubelight is still king. For those who don’t like the harsh light fluorescents generate, please note: they are also available at a colour temperature that closely resembles daylight.
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