A Step Towards a Greener Future: How can High-Performance Fenestration help to improve building energy efficiency?

Ever paused to ponder the sneaky source of uninvited warmth infiltrating your cozy corner while you are seated right by the grand windows of an esteemed commercial building, offering a sweeping view of Singapore’s vibrant cityscape? Yet, amidst this urban spectacle, an intriguing question emerges: where exactly is this uninvited heat making its entrance from? Let us embark on a quest to unravel this mystery. In Singapore’s commercial structures, double-glazed windows fortified with low-emissivity (low-e) coatings which effectively reduces heat gain through the glazing, are often used. Now shift your gaze to the thermal image shown in Fig.1 below, it’s a canvas alive with hues of yellow, green and blue, suggesting that the glazing area is indeed relatively cool with little heat gain. But what about the intense red regions seen in the image?

The red regions unveil a different narrative, one of audacious heat invasion and hint at a compelling reality: relentless heat seeping through aluminium frames and the edge of glass, pushing air-conditioning systems into overdrive. The consequence? A surge in cooling demands, spiralling energy consumption, and an inadvertent uptick in our carbon footprint.

In a world where energy efficiency is paramount, improving the thermal performance of building envelopes poses a challenge for us as we strive to reduce the overall building energy consumption. A pressing question beckons: How then can our industry address this predicament?

Fenestration frames are predominantly made of aluminium, a good conductor of heat with a material thermal conductivity of 160W/mK. To put things into perspective, that's a staggering 160 times more conductive than glass! As a result, there is considerable heat gain into buildings through the fenestration frames, which constitute a substantial proportion (up to 10 percent, and could be even more in certain cases) of a building's total fenestration area. This ushers in an array of challenges for both maintaining desirable indoor temperatures and ensuring thermal comfort for building occupants. The familiar heat you feel when sitting beside a window that is not well-insulated? Now the puzzle pieces are falling into place! 

With this, it is important that fenestration frames should be taken into account when looking at the overall thermal performance of the façade. Recognizing their significance, some countries have accounted for fenestration frames in their building regulations, and notable examples include H1 Energy Efficiency under the Building Code in New Zealand, Section J of the Building Code in Australia and the Saudi Building Code in Middle East. 

The solution to this conundrum? Thermal break technology – a solution which revolves around a simple yet transformative concept, whereby a profile made of low-conductivity material is placed between the aluminium frames (as illustrated in Fig. 2), separating the interior and exterior aluminium sections. An insulating barrier is thus created, preventing the direct flow of heat, substantially reducing heat gain through the frames. 

The thermal break profile is made of glass-fibre reinforced polyamide (PA66GF25), and it is an engineering plastic with low thermal conductivity of 0.3W/m²K (over 500 times lower than aluminum) and excellent mechanical properties.

From a thermal simulation of a stick curtain wall frame conducted using THERM software, it was found that (as illustrated in Fig. 3) between a typical aluminium frame and a thermally broken aluminium frame with a basic thermal break, there is over 70 percent reduction in frame U-value from 17.1W/m²K to 3.0W/m²K. As for the Solar Heat Gain Coefficient value, there is a 83 percent reduction from 0.309 to 0.053.

To accommodate diverse architectural and performance demands, it may at times call for the adoption of specialised solutions. For instance, situations that demand enhanced thermal insulation might necessitate the use of wider, more complex insulating profiles, while the incorporation of low conductivity foam presents another tailored solution to tackle other heat gain mechanisms such as convection and radiation.

Speaking with Professor S.K. Chou, founding executive director of the National University of Singapore’s (NUS) Energy Studies Institute, he noted: “Many have the misconception that thermal breaks are only used in other climatic regions and there is no need for its use in tropical climates such as in Southeast Asia. In the tropical regions, there is no escaping the intense heat gain arising from sunlight impinging on the building fenestrations. When buildings need cooling, the heat transmission through the fenestration frames and edge of glass determines the magnitude of the cooling load and cooling energy consumption. Laboratory and in[1]situ studies have been conducted to shed light on the performance and benefits of this unique key technology solution, dispelling the misconception that thermal breaks are relevant only to cold climatic regions. In actual fact, adoption of the technology, supported by standards, is already widespread in the tropical belt where cooling is required all year round.”

To determine the effectiveness of thermal break technology in tropical climates, a study was conducted at the Building Construction and Authority (BCA) SkyLab, a state-of-the-art testbed facility which allows technologies to be tested under real-world conditions at different building orientations. The study, which was conducted by BCA, NUS, and Technoform (as the industry collaborator), and funded by National Environmental Agency (NEA) under the Green Building Innovation Cluster (GBIC) project, found that a thermally broken window system reduced peak heat flux by 59 percent.

In a quest to delve deeper into this issue, Technoform conducted a building energy modelling in collaboration with a third-party consultant, which yielded an impressive revelation: there is a 28 percent cooling energy consumption reduction when comparing thermally broken and non-thermally broken systems. These findings are not just a statistic – they serve as a real-world testament to the tangible benefits that can be realized through the adoption of thermally broken frames, as opposed to the common belief that its impact may be limited. For more information on the studies, please contact Technoform directly to find out more: info [dot] tesg [at] ap [dot] technoform [dot] com.

Through such efforts, Technoform hopes to pave the way for more informed decision-making by developers, architects and consultants in building design, ensuring stakeholders do not underestimate the amount of heat entering the building. The application of thermal break in tropical climates is not only viable but also essential in the pursuit of greener, more energy-efficient buildings.

Beyond the aluminium frames, heat will also enter through the edge of the glass. Typically, double glazed units are separated by aluminium spacers, which have high thermal conductivity, resulting in substantial heat transmission at the edge of glass. A warm edge spacer, which is a thermally improved hybrid spacer, can help to overcome this challenge.

The improved spacer has a linear thermal transmittance almost 2 times better than traditional aluminium spacers. Hence, when a warm edge spacer is used in place of an aluminium spacer, the edge of glass heat transfer will be substantially reduced. Technoform Warm edge spacers can be found in notable building projects such as the Apple Store in Bangkok (Fig. 8) and Suntec City in Singapore (Fig. 9).

Amidst the backdrop of Singapore’s relentless pursuit of sustainable architecture, one notable case study is the PSA Tuas Port Maintenance Base, which consists of 8 buildings that serve various aspects of maintaining the port facilities. One of them is a 6-storey Administrative Building, which is the first major building to be completed in Tuas Port. It has been awarded the Green Mark Award (Platinum) under the Super Low Energy Building (SLEB) category by Singapore’s BCA, highlighting its best-in-class energy performance and stands as a testament to the building’s exceptional energy conservation achievements.

PSA Corporation Ltd championed the implementation of a high-performance curtain wall system, targeting for an overall U-value performance of less than 1.8W/m2K, which on top of the glazing, also includes the performance of the frame and edge of glass in accordance to international standard ISO 12631. In pursuit of this demanding requirements, Technoform thermal insulation solutions were adopted, seamlessly meeting this exacting standard.

As the world continues to grapple with the challenges of climate change and the emphasis on greener buildings continues to grow, high-performance fenestration systems are poised to play an increasingly vital role in making buildings around the world more energy efficient. This also closely aligns with the goals set forth in Singapore’s Green Building Masterplan, as the adoption of high-performance fenestration systems contributes to substantial building energy savings, lower greenhouse gas emissions, and overall, a more sustainable built environment. “The adoption of high-performance fenestration, a key component of any building, is no doubt an essential strategy in the pursuit of our net zero future.” Benjamin Teoh, Technical Specialist of Technoform Bautec Asia Pacific, noted.