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Light Shelf – 3 Reasons on why it is the feature of High Performance Building in the Tropics

It is the element that anyone can relate to, Light. There is no doubt, the field of photobiology has proven the significance of light towards our circadian rhythm. However, the disappointment may be the lack of understanding from the built environment industry, while the language of aesthetic value in buildings has been always on the sketch book of Architects, many have failed to understand the fundamental of a biophilic buildings, the very built environment that we need that connects us to nature better. One crucial aspect of it is the usage of Daylight. As some of you may know, i am on my investigation to the effectiveness of daylight and task light for office space as part of my Msc thesis, part of the reason that motivated me so much in trying to understand lighting design was my office space in my previous architecture internship.

Lighting Office Scenarios

Daylight for the Office Space – The language many still do not Appreciate

Lighting matters in an office space, a good lighting system can save the energy usage while not sacrificing office occupants’ visual comfort which will affect their productivity. However with the invention of artificial lighting, many architects have preferred to do away strategies to harvest natural daylight and rely on artificial lights during the day time. Such a waste! The best quality of light remain untapped! The picture above illustrates 3 example of lighting strategies, as you can see the left one has induced glare into the office space (judging by the obvious luminance ratio), the one in the middle was actually my work place that i really hated, the right one is an example of good daylight distribution across the office space.

There are many creative ways of getting daylight deeper into your office space. In this write up i am going to write specifically on the 3 reasons why light shelf is part of the design of high performance building in the tropics. I will not go into the details of light shelf however, but i will like to highlight on 3 reasons that also debunk 3 common myths on the usage of light shelf in the tropics, as some have regarded it as an architecture element coming from the west.

GEO Building Exterior Look
Green Energy Office @ Bangi, details showing Light Shelf

1) Light Shelf does not induce additional heat into Indoor AC space

Light shelf shall not harvest direct sunlight into the office AC space. The reason is obvious, significant heat gain will be brought in and glare will be allowed in the office space, and you will find people covering the entire light shelf eventually.  There is a difference between direct sunlight and diffuse daylight. One shall only reflect in diffuse daylight, thus which is much lower in heat radiation. Some may say that the louvers will be ‘heated up’ and radiate heat into the indoor space, this will not happen as it is only for glare prevention for steep morning/evening sun for the west/east facade.

Raytrace Simulation of ST

Then you may ask me why are these louvers needed for North and South orientation, this is because the source of glare is not necessary from the sun alone but diffuse sky sometimes can be a source of glare as well when being viewed from indoor. This entire facade system, example from ST Diamond Building, is how one can ensure diffuse light is distributed evenly throughout the office space while there is no risk of any glare as a result from poor luminance ratio. The daylight is well distributed, thanks also to higher ceiling height by taking off the ceiling panels and painting the ceiling white, thus allowing a higher bounce of natural daylight.
ST Diamond Interior Office
The detail of the light shelf, there is also roller blinds for the bottom portion to allow occupants  to control the uniformity of incoming daylight, while this does not affect the overall room daylight distribution coming from the light shelf. Furthermore, ST Diamond building  is designed to the form of a diamond, which helps in being self shape and also preventing potential glare.
ST Diamond CLose in Light Shelf

​2. Harvesting Daylight does not only saves Electrical Energy from avoiding the need of artificial lighting, but saves internal AC load instead

The fact of  ST diamond building and Green Energy Office in Bangi is, artificial lights are so rarely on, most probably only 5% of the time. And there is feedback from the deputy CEO (who is housing GEO Building) that they have yet to change the T5 tubes after 7 years of operation. The lighting power density of ST diamond building is only average of 0.9W/m2, that is 95% of savings compared to the MS1525 recommendation of Lighting Power Density.
Lighting Power Density of ST

​Also, by having lesser electrical lighting, this also means lesser indoor AC heat gain in respect to the law of thermodynamics where any electrical wattage of indoor space will be eventually converted to heat gain for indoor AC. Below is an illustration of the breakdown of energy consumption of a typical office, as you can see, lighting heat gain is significantly one fifth of the AC load.

BSEEPBreakdown
In addition to that, the quality of diffuse light is much higher efficacy compared to artificial lighting, thus if we compare the same overall luminance output for both daylight and artificial lighting, the heat load from daylight is much lower than that of artificial lighting. This is because daylight has a higher efficacy compared to electrical lighting as illustrated below.

Lighting Efficacy Comparison

​3. The benefit of Daylight is Abundance, and often underestimated.

The last point is on the benefit of daylight, there are many literature citing on the benefit of daylight when it comes to office ergonomics, provided that the office is designed right to prevent glare and poor uniformity of light. It is also part of the benefit of biophilic architecture in ensuring that occupants are connected to the external outdoor view rather being captivated in a routine office work space. I will not share much on this however i am attaching a peer review report citing dozens of literature on this matter.
Just some additional picture to show the daylight distribution measured in Green Energy Office Bangi..

DaylightMeasurement

 

 

An example of a lecture on going in a 100% daylight assisted room, way much more pleasant compared to artificial down lights. Don’t you think so?

GEO Interior Meeting Room

The Green Energy Office is also designed in such a way that the light shelf is placed along North and South orientation while the building self shades itself, it is understood that the sun path in Malaysia will have a maximum of 63 degrees sun angle from floor plane for both North and South, thus it is relatively easy to shade against direct sun light.

GEO Visit_00019

 

So what do you think about the application of Light Shelf in the tropics? These are examples of projects in Malaysia already done with light shelf and has proven to be a significant component in the overall high performance building to bring down energy usage and hence also shorter payback period. Here i attach some of the key facts of the mentioned building.

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