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Daylight – The Forgotten Light for Office Space

It is ridicule to think about installing solar panels while we do not even attempt to daylit our office spaces in the Tropics. Why the need for expensive, long-term investment on renewables when there are relatively cheap (or even free with energy conservation) energy efficient design methods via passive design such as daylighting? With the sunshine all year round, it is a paradox that many building professionals and clients seem to immerse into the aesthetic and monetary value of their design products instead of understanding the ‘biophilic’ design aspect of the building to live in – the interaction with the sun and the climate. Rightfully, daylighting is a civil matter in the UK, administered by the “Right to Light” law which prohibits new development from interrupting daylight getting into any windows of its nearby buildings. Sadly, similar rights and laws in the USA were abolished following the introduction of electric lighting in the mid of 20th century. The finger plan school layout in the California was also abandoned with the invention of air conditioning then, due to the concerns of thermal heat gain from huge glazing openings.

Benefits of Daylight & Daylighting

The critical importance of daylight associated with human health, happiness, well-being and performance are understood since the ancient civilisation as well as in modern healthcare. It is a fundamental healthy architecture design that is resurfacing with the recent green building movement. People generally prefer daylight predominantly with supporting electrical lights for their work spaces. Considering most of the office task today works from an illuminated visual display, daylight functions well as an appropriate ambient light source to complement with. Some would prefer the variation of lighting level throughout the day that hints the outdoor weather condition, while some would prefer a task light instead that empowers them to customize their personal workspace luminous environment. It is one of the many workspace psychology factor that affects mood and work productivity. Most importantly, the forgotten light is also beneficial in non-visual aspect, by regulating our circadian. It has significantly higher blue wavelength (464nm) in its spectrum as compared to that of our office conventional lighting which will suppress the production of melatonin by the pineal glands. The secretion of melatonin assists our bodies to sleep. This explains jet lags and your difficulty of falling asleep after browsing through your bright phone in the dark.

But why aren’t we getting it Right?

The art of daylighting is easier said than being done. It has to take the surrounding obstacles, sun path, interior design, electrical light controls and work culture into account to understand occupant behaviours with their lighting environment. It bothers me when a local press quoted that green building has large glazing to enable plentiful of incoming daylight. Just look around our office towers with all the roller blinds pulled down due to sources of glare from bright sky, not only direct sun! Subsequently, that shuts out the incoming daylight from the vision window and hence the total reliance on electrical light. The trick is to distribute only diffuse light deeper into the office space uniformly, while ensuring direct sun is shaded off (which also helps in reducing radiation thermal loads that saves air conditioning cost). There are many ways to daylighting, from the façade via light shelf, from the top via light pipes, from courtyards, or even fibre optics and many advance technologies. Eventually a successful daylight system is one that is proven with reduction of electrical lights that shows daylight interaction and occupants visual comfort acceptance. This article will share one of the latest project consulted by IEN consultants, which pioneers the usage of daylight trough in this region.

Daylight Trough in Menara MK Block D

The conventional daylighting strategy utilizes light shelf which bounces off incoming diffuse light to the ceiling above and spread it throughout the office space. Instead, the approach taken by the daylight trough, in Menara Mustapha Kamal Block D, guides the diffuse daylight in and exit the aperture which flushes in as a ceiling panel. The 21 stories provisional GBI Gold certified office tower in Damansara Perdana has an average of 1,193m2 of net lettable area per floor with office depth ranging from 9-16 meters and alternate level of sky gardens. In terms of daylighting performance, the performance of the daylight trough is superior to that of the conventional office. Under the definition of useful Daylight Factor (1-3.5%) by Green Building Index, the result shows that the daylight trough is capable of delivering up to 6 meters into the office space. This measured result is taken in prior of occupancy with the blind assumed fully in rolled down as shown. It also compares with the lighting simulation tool, Radiance from IES-VE software and proving it’s a reliability with a significant correlation in result (r=0.7577).

Cross section illustration of the daylight trough and line chart of Daylight Factor and Illuminance performances
Cross section illustration of the daylight trough and line chart of Daylight Factor and Illuminance performances

Various scientific literature have shown that human subjects are capable to adapt to ambient daylight illuminance range from 200-2000 lux (sometimes we even measured as low as 100lux during laptop usage). As shown, the 3 different electric light circuits are controlled by the lux sensor with the set point of 250 lux. However, the provision of an ergonomic task light was also proposed to ensure localized lighting control. The depth of the sun shading slab works well to shade the interior from direct sun, which has the lowest altitude of 65 degrees. Hence, the variation in illuminance contributed by the daylight trough will not be dramatic as it is independent of direct sun. In terms of energy efficiency, the calculated lighting power density for the office is 5.25W/m2 and 1.90W/m2 without and with the assistance of daylight trough, both well within the MS1525:2014 maximum requirement of 10W/m2. Using the annual hourly weather file for Kuala Lumpur, the electrical lighting savings from daylight system by on/off controls of the lights is as high as 39.2%. The anodized reflectivity material within the daylight trough is MIRO95ax4 Extra Bright from Alanod, which means having reflectivity of 95%. It has to be noted that the diagram shows the north oriented office receives low illuminance from the similar daylight trough as oppose to the south oriented office. This is due to the surrounding obstacles as the north oriented office faces another tall office building and Flora Damansara hill as the obstacles, while the south oriented office faces the open skyline of Mutiara Damansara.

Interior perspective picture of the daylight trough with the bottom right as the exiting aperture
Interior perspective picture of the daylight trough with the bottom right as the exiting aperture

Aspects of Considerations and Challenges

The design of the daylight trough has to cater for three objectives; constructability considering all other mechanical and electrical components in the ceiling space, maintenance of the daylight trough (as dust affects daylight bounce) and daylight performance. The design of the daylight trough does not span across entire ceiling space as there are pockets of ceiling space for fresh air ducts and fire sprinkles (as shown). The daylight trough design only caters for the centre of the office space as the corners with shallow depth should get sufficient daylight from fenestration alone. While conventional office typically ignores the hidden space above the ceiling which offers the flexibility of laying the components anywhere, this one does not. The initial daylight trough design had the upper light trough tilted to allow redirection of daylight deeper into the space, however this was later revised due to constructability considerations. The evolution of the design also considered maintenance which suggested robot vacuum cleaners every half year to clean the daylight trough. As there was an uncertainty over the robot’s navigation due to height clearance and frequent ceiling hangers, and even levelling, the act of “over-engineering” also potentially added cost. Also, the unconventional issue of additional lateral load and movements by the robot vacuum concerns the warranty of ceiling panel suppliers and various sub-contractors. With the complication of liability and potential defects, the daylight trough was redesigned to be isolated and enclosed which accumulates only minimal dust. Telescopic mops will be used via the translucent exit aperture of the system to maintain the daylight trough.

Illustrated axonometric exposed view of the ceiling components arrangement
Illustrated axonometric exposed view of the ceiling components arrangement
Illustration of revisions of daylight trough
Illustration of revisions of daylight trough

Debatable Payback Period

Well, so comes the common question, what’s the cost? The total additional cost of the daylight trough per meter square office area (Nett Lettable Area) is RM38.21/m2, which includes the additional reflective aluminium sheet from Alanold and Gypsum Board. The expected payback period for the daylight trough is 20.4 years with the consideration of operational expenditure only. The operational energy savings computes the avoided lighting energy usage with the current C1 tariff rate at the price of RM0.365 while lamp replacement cost annually is reduced due to increased lifespan of T5 electrical lights. However, the conventional payback period does not capture intangible items such as building cooling load savings, carbon tax savings, residual value, enhanced corporate prestige, and most importantly, the effect of daylight on human well-being, which potentially improves work performance. A study from Carnegie Mellon University (CMU) shows that costs of an employee is some 160 times that of energy. Conventional daylight from windows yielded energy savings of £7/m2 and annual productivity gains of £142/m2 (Mayhoub & Carter, 2011). One example which uses the whole life cycle costing (WLCC) method computes a payback period of as fast as 6 years. Besides, there are three factors affecting payback periods; electricity prices, system capital cost, and available external local illuminance. Which in accordance to the Economic Transformation Programme (ETP), electricity prices will be subsequently increased due to the removal of subsidies.

Interior perspective of the office space with the measurements being taken at far behind
Interior perspective of the office space with the measurements being taken at far behind

Further investigation on the effectiveness of the daylight trough will be done during occupancy stage later. Do the occupants improve in cognitive performance under the daylight trough as compared to electrical lights? Are they visually comfort under such variation of natural daylight across the day? Despite whatever outcome, it is high time for us to think our cities and buildings as the space to live as they shape the way we are. The fundamental of good architecture lies in functional spaces that catalyses the idealism of social cohesiveness and biophilic design. Employees spend almost half of their days in an artificial space with artificial light levels. The forgotten light, daylight, is one of the many common sense aspects to rethink how we shape our built environment today.

Reference: Mayhoub, M. S., & Carter, D. J. (2011). The costs and benefits of using daylight guidance to light office buildings. Building and Environment,