Greenjobs Blog

Illumination is one of the topics we still need to greatly improve. Most houses are still using the worst possible type of bulb, wasting a lot of energy, and some myths about energy efficient bulbs are still promoted.

Coming to talk about this, I recently read an article dismantling ten popular myths of efficient light bulbs. But… do you know the different types of light bulbs? Do you know which one is the best choice? We’ll show you.

Incandescent bulbs

Incandescent bulb: least energy efficient bulb

These bulbs produce light when an electrical current passes through a filament, usually tungsten, heating it up to about 3000 °K and making it emit light. The inside of the bulb is empty, or filled with gas, which prevents the filament to suffer oxidation. 90% of the energy taken by the bulb (usually 20 to 120 W) is irradiated as heat, instead of visible light. They produce up to 15 lumens/W.

Their useful life lasts no longer than 1000 hours in most cases. However, they are the cheapest to buy, and no lamp socket change is required in order to use them.

Still most used at households, but you must avoid them: the illumination cost with incandescent is the highest.

They are the least energy efficient bulbs and they produce a lot of heat.

Halogen lamps

Halogen lamps: slightly better than incandescent

Halogen lamps are similar to incandescent. They also use a tungsten filament but they have the bulb filled with an halogen gas which chemically reacts with the evaporated tungsten. When the electricity current passes through tungsten, a small amount of it becomes gas. The halogen reacts with it and produces light.

They have slightly better efficiency than non-halogen bulbs (up to 24 lumens/W, usually taking 20 to 60 W), but produce more heat too: their operation temperature is higher, and that can sometimes burn the paint on your ceiling! Most halogen lamps also focus the light in a certain area, and they don’t spread it room wide.

I was surprised when reading some of the safety issues halogens can cause, such as high UV radiation, bulbs exploding because of your fingerprints, etc. Please read the content of the link and take care.

Sometimes halogens stop working suddenly, so you have to replace them and it can be expensive to do this.

Fluorescent lamps

Fluorescent lamps: reaching efficiency?

Fluorescent are a further step in illumination efficiency, we are talking about 22% used energy is turned into visible light, with efficiencies from 50 lumens/W in worst case to 100 lumens/W, usually taking from 15 to 35 W.

Fluorescent lamps contain mercury vapour and phosphor. Electricity is used to excite the mercury vapour, so it produces ultraviolet light. This light itself is not visible, but when illuminating some materials with this kind of light, they emit visible light. So the ultraviolet light hits phosphor and it emits visible light.

Useful life spans of fluorescent tubes are much longer than incandescent: more than 25000 hours. But with that age, a fluorescent lamp would have lost 50% of its original brightness. Remember an incandescent bulb lasts no more than 1000 hours.

Fluorescent tubes have something interesting: they are usually long, so you can illuminate big rooms with few tubes. You must use a lot of incandescent, or even more halogens, but just few fluorescents. Light emitted by them is whiter than light from incandescent or halogen, and it’s spread room wide. However their initial cost  is higher than for incandescent bulbs.

There is another variety of these fluorescent lamps, the CFL (compact fluorescent lamp), with efficiency from 60 to 72 lumens/W (50 to 100 lumens/W for standard fluorescents). They have a small problem, if you turn them on and off quickly, their lifespan can be reduced by upto 85% . Some of these CFL’s can replace incandescent bulbs because they use the same socket. They are more expensive, but much more energy efficient.

I would recommend this kind of lamps/bulbs, as the illumination cost is lower with CFL or fluorescent tubes.

LED lamps

LED lamps: new technology for great efficiency?

These are not widely used at the moment but LED technology promises very long life spans (more than 50000 hours), high efficiency (up to 150 lumens/W), and a small size.

The problem for LED technology is they are still very expensive.

Now you know the different kinds of lamps and bulbs you can choose, consider which one fits your requirements. I would recommend fluorescent or CFL, and always try to avoid both incandescent and halogen lamps. The first ones because they are the least efficient and the energy cost is the highest with them, and the second one because of their flaws, such as focused light, high temperature, etc.

According to my experience, fluorescent tubes quickly offset their initial cost, so consider acquiring some if you plan on change your house illumination.

Maybe we’ve arrive late with this post, but it can be useful for next summer. When the temperature increases and you feel hot at home or in the office everyone wants to use the air conditioner for a cooler temperature. But, of course, that’s energy expensive, and there are several ways to keep your house a bit cooler without using an air conditioner.

1. Shut the curtains and close the windows during day. If you open them, heat will come inside.
2. Turn off your lights the longer you can, they produce heat.
3. Avoid the use of oven and other stuff which produces a lot of heat. Make a salad and eat some cold food instead.
4. Use a laptop instead of a desktop computer. They save energy, and they produce less heat too: rooms will be up to 4 degrees cooler.
5. Make a fan blow over a block of ice, and you will have a cold breeze.
6. Create a “wind tunnel”: use a fan to take cold air from the outside (at night), and other fan to exhaust hot air to the outside.
7. Use less clothes and wet your skin often. You can also put a fan close to you.

If you liked this, you can read more tricks to keep cool without air conditioner here, blog from which we have made this small list.