When you have an idea, a bulb lights up in your head, but when you really switch on a bulb, maybe you don’t have any idea of what lays behind this simple click. How much does it consume, what colour does it emit, what source is feeding it, how many lumens does it provide, does it bear any toxic substances, how long does it last, where does its light spread on? If I have to come back immediately, do I switch off the light? We want to cast light on this topic, since light abounds, specially daylight.

Natural light is essential so that the whole organism works well: it helps us generate Vitamin D , it keeps our biological clock on time, it stimulates our mind, it induces to optimism, and it makes us feel in contact with the world… Artificial lighting has not the same properties. Because of all this and in order to save energy, a first advice would be to take full advantage of sunlight.

How can we go about it:

  • The rooms where we will be staying longer, or where we will be working, should be chosen facing south and be provided with good windows.
  • Let us put the tables, sofas, etc., we want light on near the windows.
  • Let us use blinds, curtains, awnings… to regulate light intensity and prevent direct sun rays.
  • Where there are no windows we can install glass walls, translucent tiles, skylights or a solar tube, a kind of skylight that lets in the light of the roof to any level of a building.
  • Let’s go outdoors whenever we can (to take a walk, to read at a park, to meet people at a sidewalk café…).
  • Let us adapt our hours to those of daylight.

When we have to use electric light it is better to avoid either poor or blinding light, any of this can cause damage to our sight. To perform visual activities we need more light, whereas we need dim light to relax or rest, in either cases we will need to evaluate how much light we do need.

How can we go about it:

  • The light of a bulb is not measured in Watts (which measure the energy it consumes), but in lumens (Lm, it is still difficult to find them in some labels). This light spreads over an area, and the light that arrives to each point of the area is measured in Lux. We can see how many Lux we need in different situations here.
  • In order to know how many lumens we need, we have to multiply the Lux we want by the square meters on which the light is spread. If the bulb is near, less lumens are needed to obtain the same Lux.
  • If we are doing a visual activity it is important to have an adequate lighting upon the area we need well-lit (the book, the working area…). In those cases the directional bulbs are the appropriate choice. The light they provide is not measured in lumens but in candles (Cd), to know how many we need we have to ask the vendor (the calculation of Lux depends on the magnitude of openness of the spotlight).
  • One light bulb consumes less than two or more adding up to the same power.

To carry out our work we need plenty of cold light, to relax, we need warm dim light. On the other hand, colours look different in artificial light than what they do in natural light. To get a good illumination it is important to focus on the type of light provided by the bulbs we can buy.

How can we go about it:

  • Whether the light is warm or cold depends on the tone. Incandescent bulbs provide warm light, halogen ones neutral light, the rest can provide warm or cold light (we have to pay attention when we choose the model).
  • The ability of a bulb to reproduce natural colours is measured by CRI (colour rendering index) or Ra. Common values are above 80. If we need to see well the colours it has to be of 90. The bulbs that do not have a good rendition of colour are those of low consumption or fluorescent lamps and LED's.
  • We will often find a number of three figures such as 927 or 840 indicating both the tone and the CRI in this way.

Low consumption bulbs consume five times less power than conventional ones and they last up to 10 times more, but their manufacture and disposal of waste are more complex. We can evaluate the uses for which it is better to keep using the incandescent or halogen ones.

How can we go about it:

  • Cases in which it is better not to go over to low consumption bulbs: those which we use very little, those in which the risk of breaking often is higher, and also in those cases in which it is important to see well natural colours.
  • Here we have a summary of the characteristics of each type of bulbs.
  • We should think that the contribution of bulbs for domestic use to climate change is a very small one (1% for instance in the case of Spain). This 1% is as important as the rest of factors, but we cannot take it as a symbol and placebo and forget the wasteful nature of the energy and economic model. It is infinitely easier to change bulbs than the economical structure, but if we don’t change the structure, changing bulbs will be almost useless.

Natural light is essential so that the whole organism works well: it helps us generate Vitamin D , it keeps our biological clock on time, it stimulates our mind, it induces to optimism, and it makes us feel in contact with the world… Artificial lighting has not the same properties. Because of all this and in order to save energy, a first advice would be to take full advantage of sunlight.

How can we go about it:

  • The rooms where we will be staying longer, or where we will be working, should be chosen facing south and be provided with good windows.
  • Let us put the tables, sofas, etc., we want light on near the windows.
  • Let us use blinds, curtains, awnings… to regulate light intensity and prevent direct sun rays.
  • Where there are no windows we can install glass walls, translucent tiles, skylights or a solar tube, a kind of skylight that lets in the light of the roof to any level of a building.
  • Let’s go outdoors whenever we can (to take a walk, to read at a park, to meet people at a sidewalk café…).
  • Let us adapt our hours to those of daylight.

When we have to use electric light it is better to avoid either poor or blinding light, any of this can cause damage to our sight. To perform visual activities we need more light, whereas we need dim light to relax or rest, in either cases we will need to evaluate how much light we do need.

How can we go about it:

  • The light of a bulb is not measured in Watts (which measure the energy it consumes), but in lumens (Lm, it is still difficult to find them in some labels). This light spreads over an area, and the light that arrives to each point of the area is measured in Lux. We can see how many Lux we need in different situations here.
  • In order to know how many lumens we need, we have to multiply the Lux we want by the square meters on which the light is spread. If the bulb is near, less lumens are needed to obtain the same Lux.
  • If we are doing a visual activity it is important to have an adequate lighting upon the area we need well-lit (the book, the working area…). In those cases the directional bulbs are the appropriate choice. The light they provide is not measured in lumens but in candles (Cd), to know how many we need we have to ask the vendor (the calculation of Lux depends on the magnitude of openness of the spotlight).
  • One light bulb consumes less than two or more adding up to the same power.

A high contrast of lights strains our sight. Fluorescents do not consume much more power when they are switched on, but their life cycle is shortened by switching on and off. For our health’s sake and for sustainability it is necessary to pay attention to how we use bulbs.

How can we go about it:

  • For reading or working we install a powerful light directed to the surface to be seen and a general dim light. We must not have naked bulbs in our field of vision.
  • Don’t leave on lights that you don’t need. But if you go out only for a while from a room with a fluorescent (or a low consumption bulb), it’s better not to switch off the light.
  • Attenuation bulbs spend quite a lot more regardless of the intensity to which they are set. It is better to put them off using the switch than using the attenuator.
  • Hints to spend less power: give lamps and bulbs a dust, paint walls and ceilings in light colours, avoid using indirect lights. To decorate with electricity is luxury; let us avoid ornamental lights aimed only at pictures, plants…
  • When they blow out, let us take all type of bulbs to a waste collection service.