“We must not fear daylight just because it almost always illuminates a miserable world.” – Rene Magritte
Daylighting is the controlled admission of natural light into a space through fenestrations such as windows or skylight to reduce or eliminate the use of electric lighting. By providing indoor spaces with a direct link to the dynamic patterns of outdoor illumination, daylighting helps create a productive, health and stimulating environment for building occupants, while at the same time reducing as much as thirty percent of the total building energy costs.
There is such a thing as too much daylight. As the architect conceptualizes the design of the building, he balances his daylighting design not so much on how to provide enough daylight to an occupied space, but how to do so without any undesirable side effects. This involves more than just adding windows or skylights to a space but rather, the careful balancing of heat gain and loss, glare control, and variations in daylight availability. A good example of successful daylighting designs will invariably pay close attention to the use of shading devices to reduce glare and excess contrast in the workspace. He evaluates the proper window size and spacing, glass type selection, the reflectance of interior surface finishes and the location of any interior partitions.
Benefits of Daylighting
“The cause ceasing, the effect ceases also.” – Edward Coke
When properly integrated and designed, daylighting has the potential to significantly improve life-cycle cost of the building. An estimated incremental first cost increase of from P0.57 to P0.85 per square meter of occupied space for dimmable ballasts, fixtures and controls, daylighting has been shown to save from P0.06 to P0.22 per square meter annually [in 1997]. This is true among schools and commercial buildings in the United States but would also be very much applicable in the Philippines.
Daylight enlivens spaces and has been shown to increase user satisfaction and visual comfort leading to improved performance, this increases user health and productivity. By reducing the need for electric consumption for lighting and cooling, the use of daylight reduces the emission of greenhouse gases and slows fossil fuel depletion.
Electric lighting accounts for 35 to 50 percent of the total electrical energy consumption in commercial buildings in modern cities. Electric lighting generates waste heat and also adds to the loads imposed on a building’s mechanical cooling equipment. Daylight integration reduces operations cost by reducing or eliminating the need to electrically power lights. The energy savings from reduced electric lighting through the use of daylighting strategies can directly reduce building cooling energy usage an additional 10 to 20 percent. Consequently, for many institutional and commercial buildings, total energy costs can be reduced by as much as one third through the optimal integration of daylighting strategies.
However, as with any energy-efficient design strategies, there are higher initial costs associated with the use of daylight and electric lighting. Architects must also be aware and avoid glare and overheating when placing windows; more windows do not automatically result in good daylighting. Natural light has to be controlled and distributed properly throughout the workspace [evenly] to achieve the desired comfort and efficiency. Realistically, for cost savings to be realized, luminaries and controls have to be in proper functioning order. Poor installation, commissioning, or Operations and Maintenance (O&M) practices can all lead to sub-optimum performance.
Practical Design Concepts
“When man becomes reconciled to nature, when space becomes his true background, these words and concepts will have lost their meaning, and we will no longer have to use them.” – Michelangelo Antonioni
It is important to appreciate that the daylighting design process involves the integration and input of many professionals and disciplines, including architectural, mechanical, electrical, and lighting. This design team members need to be brought into the process early to ensure that daylighting concepts and ideas are carried throughout the project. One should look into parts as a general whole; this “holistic” design process will weld the different aspects that affect the daylighting design of spaces. As the head of the team, the architect should actively direct the other professionals towards one common goal which has been envisioned for the building or space.
Awareness of the basic visual acuity and performance issues is essential to an effective daylighting design.
1/ Veiling Reflections
Off the Internet, Veiling Reflections are reflections which partially or totally obscure the details to be seen by reducing the contrast. Due to reflections of high brightness light sources off specular or shiny surfaces, they obscure details due to reduced contrast. They should be avoided, particularly where critical visual tasks occur.
Introduce as much controlled daylight and as deep as possible into a building interior. The human eye can adjust to high levels of luminance as long as it is evenly distributed. In general, light which reaches a task indirectly will provide better lighting quality than light which arrives directly from a natural or artificial source.
The aim of an efficient daylighting design is not only to provide illuminance levels sufficient for good visual performance, but also to maintain a comfortable and pleasing atmosphere. Glare, or excessive brightness contrast within the field of view, is an aspect of lighting that can cause discomfort to occupants. The human eye can function quite well over a wide range of luminous environments, but does not function well if extreme levels of brightness are present in the same field of view.
Variation in brightness levels may be desirable in a space for visual effectiveness. Dull uniformity in lighting can lead to tiredness and lack of attention; both are incompatible with a productive environment. Often times a good daylighting solution will integrate a “blast” of beam daylight in a circulation area for visual interest and to help lead occupants through a building. The human eye is naturally attracted to this bright area and can be useful in guiding people down an otherwise insipid corridor.
Good daylighting requires attention to both qualitative and quantitative aspects of design. Make sure the combination of natural and artificial sources provides adequate light levels for the required task.
Around the world, like the Illuminating Engineering Society of North America publishes an industry-standard method for determining recommended illuminance levels tha are expressed in units of footcandles (fc) or lux (lx) for various tasks. A minimum of 50 footcandles [538.12 lux] on an imaginary desk-height horizontal or “work surface” is recommended for office spaces; nevertheless, when used in conjunction with indirect an ambient lighting system and direct task lighting, a high-quality daylighting design can be achieved with ambient lighting levels of 30 footcandles [322.91 lux] or less.
To be effective, daylighting must be integrated with electric lighting design. In particular, daylighting must be coupled with efficient electric lighting controls if net energy savings are to be realized. As part of a daylighting design, consider the use of continuously dimming fixtures controlled by luminous sensors – expensive, but the long term saving surpasses the initial cost.