Isn’t it curious, if not appalling, that in a tropical location like ours, most of our buildings rely on electricity-powered lighting even at midday. Switching over to devices that harvest sunlight is a smart option.
If you are wondering about the expense, the cost of installing these natural day-lighting devices will be recovered as electricity savings in a span of months, or a few years at the most. Besides, you will continue to save on electricity use. And since day-lighting devices do not need to be periodically replaced, there is no recurring expenditure. Meanwhile, while day lighting is an eco-sensitive option as it lowers the carbon foot print of the building, it also bears a positive impact on the people using the space. Research shows that day-lit spaces enhance visual comfort and productivity, reduce absenteeism, improve general health, food habits and the body’s inherent biological rhythms, and even promote a sense of well being. What is more, many of these devices can be retrofitted into pre-existing buildings. We can also design for diffused day lighting or spot lighting, as the need may be. So then, let’s make the most of our place under the sun.
Light tubesHow about light tubes rather than tube lights? The light tube may be used on any floor and even light up a central corridor lined by walls on either side, as has been done at the newly renovated Bell Hotel in the city. Here, 15inch-wide light tubes lined with reflective inner surfaces bring in light from the outside, from the rear end of the building. The pipes traverse the ceiling space of the corridor and end as polycarbonate domes on the ceiling and shower light into the corridor and cafe. These domes resemble and function like light sources and give lighting until about 4 or 5 p.m. “This particular light tube is about 20 feet long and cost about Rs. 40,000. Without this light tube, this commercial establishment would have spent about Rs. 800 a month on electricity for equivalent lighting; if you add the cost of electricity-dependent light fixtures and fittings to this, it becomes clear that in about three years, the establishment will recover the money spent on the light tube,” says Sumitra Vasudevan of APRObuild, Interior Designer and LEED (Leadership in Energy and Environmental Design) accredited professional, who set up this lighting system for Bell Hotel.
Go for glassWe have always had traditional skylights and sky lanterns. But these would work only for single storey structures or for the top floor. Toughened glass blocks would facilitate a more widespread use, and can be substituted for portions of walls, and can bring in light to spaces where open-able windows are not an option.
Likewise, toughened glass walls can be substituted in places for masonry walls, as has been done by Siddarth Money, architect, KSM in the Vadhiraja building in Chennai. “Ordinary glass would let in more heat too. To prevent this, we may use performance glass with a special coating and lamination for strength and thermal insulation,” says Siddarth.
Windows“Windows are best located on the northern walls and roofs (in case of sloping roofs) to get in diffused daylight without letting in much heat. The eastern wall is the next best option, as solar rays are gentler in the morning. If the windows are to be placed on the western side, introduce a filter like verandah or balcony,” says architect Xavier Benedict, Anameka. The recommended ratio of window surface area to wall surface area is 1:3.
Lighting from windows is further enhanced by making the inner edges of the window opening larger than the outer opening. Even if the windows have to be kept closed, they can let in light if toughened glass window panes are used, instead of opaque shutters. We might also use tall, vertically shaped clerestory windows wherever the ceiling space permits it. We could also position slits on the walls, just below the ceiling to let in light. “This will let hotter air to move out of the room and keep the room cool,” Xavier suggests.
You might also check out the other day lighting options that are available such as light reflectors, light shelves, heliostats, hybrid solar lighting, etc. Finally, do opt for a white-based colour scheme within the building, as it enhances reflection of light and has a multiplier effect on lighting.
