In this article, I will provide a case study on how the daylighting autonomy for one of our projects was optimized through collaborative efforts and integrative design from various stakeholders involved in the delivery of the project. In our experience with high performance and energy efficient buildings design, we’ve often found that such collaborative efforts would yield innovative yet practical solutions as each stakeholder presents strong technical knowledge and recommendation relating to their field.
The Menara Kerja Raya office tower was designed and constructed between 2010 to 2014. The building achieved final GBI Platinum in 2016, becoming the 1st high-rise office building to achieve this accolade. You can read more about this project on our Projects page as well as from the article published in FuturArc magazine (Nov-Dec 2017 issue). IEN Consultants worked on this project as the energy efficiency consultant as well as the green building certification consultant.
With such an ambitious sustainability target, we knew we had to ensure that the project could leverage on good daylight autonomy in order to not only achieve good overall building energy efficiency (Menara Kerja Raya achieved a Building Energy Intensity, BEI of 91kWH/m2*year at GBI Completion & Verification stage) but also producing better indoor environments by allowing daylight access to more occupants.
We eventually demonstrated that more than 44% of the net floor area achieved Daylight Factor (DF) between 1.0% to 3.5%, which is the recommended range for usable daylighting levels in an office environment. What was even more impressive is that this project demonstrated that it was possible to have more than 50% of the office lights turned off during the day – a strategy that helped reduce lighting power as well as cooling demands
I mentioned at the start of the article that this is a case study of good collaborative efforts among the stakeholders. I shall provide some insight to how this came to be.
If you have ever visited any government offices in Malaysia and taken note of the workstations design – you would have probably noticed that the general trend is for these offices to utilize workstations with high partitions of at least 1.5m to offer the occupant some privacy.
From early on we encouraged the designers of Menara Kerja Raya to push for an open office design for majority of the workforce in each floor as the most effective approach to meeting the 5meter facade perimeter daylight requirement. To push the daylighting and view-out goals even further, even private offices were proposed to have transparent glass partitions so as not to block daylight and view from interior spaces. However, in the initial interior design proposal, like many office designs, the circulation corridor was positioned deep in the floor space, closest to the building core. This made logical sense since priority would be to place the workstations and employees closer to the façade for better view-out.
Using Radiance in IES to simulate the daylighting levels at the office, we could see that usable daylighting for reading and writing (Daylight Factor between 1.0% to 3.5%), could only reach approximately 4.0meters from the façade. This means that if the original interior furniture layout was adopted, only the lights above the row of workstations directly next to the façade could be turned off regularly, which is less than 30% of the total lights on a typical floor. This would have a rather significant impact on the overall energy usage of the building.
This finding was raised to design team and various solutions were considered – including ways to redirect daylighting deeper into the space, strategies to select lights with even lower power, providing lower overall background with supplement desk light – but all these strategies were either too expensive to implement or would require significant abortive work since the tower construction was fairly advance.
Eventually, after quite a few brainstorming sessions between the IEN, the architect, the interior designer as well as the builder, a simple and practical solution which had minimal impact to cost and delivery time of the project was found. The solution was to move the location of the circulation corridor to the middle between 2 rows of workstations.
Since it was no longer possible to change the building design to increase the floor area that could achieve the Daylight Factor of 1.0% to 3.5%, the design team switched strategy to make best use of the slightly lower daylight factor between 4.0m to 5.0m from the façade. Daylighting at this depth may not be sufficient for frequent reading and writing associated with office work, but it is definitely sufficient for circulation.
With the revised interior design layout, we could now expect the more than 50% of the electric lighting to be turned off when there is sufficient daylight.
In many buildings, the daylighting and view-out falls short during operation as compared to how it was envisioned and modeled during the design phase due to occupant behaviour. For ease of cleaning and reducing cost of installation, many office buildings are provided roller blinds, either solid or perforated, to allow occupants means to reduce discomfort glare. Unfortunately, when lowered, even perforated roller blinds cut out about 90% of the daylight into the space. This cuts out daylight access to all but the occupants seated right next to the window.
Anticipating this problem at Menara Kerja Raya, we proposed the adoption of perforated venetian blinds with limited adjustment angles. The individual venetian blades operating angles is limited from horizontal to about 120deg. This avoided occupants from fully closing the venetian blinds, whilst allowing good glare control.
Although these horizontal venetian blinds would require a bit more effort to clean, they present many advantages over roller blinds, as explained in the visual below