Since the invention of the light bulb in the late 1800s, the use of artificial light has swept the globe as a ‘must have’ in every home and office, largely due to the option for increased productivity. However, the result of having these luxuries so readily available has dimmed our desire to use natural light to the point where it has been largely neglected in the design of many of our buildings. It has now become easier to flick a switch than to open a blind. Unfortunately, this is not a sustainable mentality and it is costing the planet, and us, more than it’s worth.
So we ask ourselves: What other, more environmentally friendly ways are there to light our homes and offices, what are the benefits and why is natural lighting so important?
Accepting the concept
Daylighting is a practice that incorporates the use of strategically placed windows, skylights and reflective surfaces in order to control the levels of natural light penetrating a building. These techniques are employed to maximise the use of natural light in the daytime, when it is readily available, instead of relying on artificial norms. But, it’s not all about increasing the amount of sunlight in a building. The design to use natural light also involves reducing glare, managing daily changes in light levels and controlling heat gain and heat loss. Basically, daylighting aims to create an indoor environment that has a lower worldly impact, while providing a more pleasant user experience.
What’s so great about natural light?
- Cost – Nothing, it’s absolutely free!
- Uses less electricity – The more natural light that is used in a building, the less electricity is wasted on unnecessarily lighting a dark room in the daytime, when there is plenty of light roaming around outside.
- Has a smaller carbon footprint – Less electricity usage means fewer CO2 emissions and a lower carbon footprint for your buildings concrete feet.
- Saves money – Less artificial light saves money on your electricity bill, it also reduces maintenance needs, and your light bulbs last longer as a result.
- Less heat – Less artificial light means less internal heat build-up. Less heat requires less cooling.
- Happier people – Increased user satisfaction and productivity has also been noticed with effective natural lighting solutions. When people can see better, they feel better.
How does one go about using natural light in a building?
The trick is in the design. A building needs to capitalise on the use of natural light without sacrificing energy efficiency. This is because with large windows you get good light and great views, but the bigger the window the lower the insulation value of the house, and it becomes a trade-off.
So, if there are no other means to keep heat from escaping or entering a room, a window should ideally make up about 15% of the wall area in order to provide enough light (among other factors, like reflectivity). If there are measures in place to control direct sunlight and heat entering and exiting the room, the window area can make up between 30-40% of the total wall area without compromising insulation gratification. Also, because the sun doesn’t shine at night, a building designed to use natural lighting still needs to integrate electric lighting, albeit in a way that maximises the efficiency and effectiveness of the artificial light, in order to further reduce electricity needs.
Lighting the way
- A combination of these methods can be used to create an office or home environment that has easily adjustable light and heat levels.
- Skylights – Skylights are usually placed in a sloping ceiling or roof to let in natural light. They are extremely effective at lighting up a dark room, loft or office space during the day by allowing large quantities of sunlight to enter.
- Tunnel lights – Tunnel lights are placed in roofs that are separated from the ceiling by some distance. They are used where windows and skylights are not practical or where windows cannot be built in, such as isolated bathrooms. A sunlight-collecting lens on the roof is connected to a light-diffusing lens inside the room via a highly reflective vertical tube. This method takes up an incredibly small amount of space, but reflects the light around the room effectively, eliminating the need for light bulbs in the day.
- Coated glazing – Glass windows and skylights can be tinted to help reduce heat gain by blocking out external suns rays, but this also restricts access to light. Alternatively, they can be given a low-emissivity coating (high reflectance, low absorbtion) that restricts heat transfer through the glass, but still allows plenty of light to enter. The latter also helps to keep heat inside a building when the sun no longer shines.
- Internal reflectivity – Reflective surfaces can be used to further increase the depth of incoming light penetration and dispersion. Floors should be about 20% reflectivity, walls should be more than 50% and ceilings should be over 80%. Reflected light is easier on the eye than direct, natural light or artificial light.
- Ceiling slope – Incoming light is reflected by the ceiling down onto the room below, resulting in a similar effect to that of an artificial down lighter.
- External shading – Balconies, overhangs, adjustable eaves, light shelves and slats can regulate light penetration into the windows of a building. This provides greater control over light levels and more flexibility when managing internal heat levels at the hottest time of the day.
- Internal blinds and curtains – Blinds can be installed to block excessive light and to stop heat from escaping or entering. These are also adjustable for increased user satisfaction.
- Window considerations – The positioning, spacing, size, shape, number and function of the windows in a building, as well as the orientation of the building in relation to the sun, play an important role in the amount of sunlight that is received and how far this light will reach indoors.
- The sun and the seasons – The path of the sun in the day and the change of the sun’s seasonal angle are factors to consider when designing an effective daylighting system.
- Double glazing – Double glazed windows are effective at insulating rooms and preventing said rooms from gaining or loosing too much heat.
- Plants and trees – Plants and trees can be added or removed depending on the light level requirements for that specific room or window.
When the day is done
The use of natural light is essential for any new green home or office. Besides not needing to use artificial lights in the day and maximising the degree to which sunlight penetrates a building, natural warmth from the sun can be used and exploited to lower artificial heating costs, especially on cool, clear winter days. The less lighting and heating we use, the less strain we put on the environment, and our bank accounts. By utilising the sun’s energy indoors, a building can take a stand for sustainability, simultaneously obtaining better views of the outside world and the sky, adding aesthetic value to any room and promoting a more appealing indoor environment.