Sustainability in modern glass facades and buildings is probably the most important contributor towards a reduction in greenhouse gas emissions, where carbon dioxide represents the largest share.
Cover image: The headquarters of the International Olympic Committee (IOC), Olympic House is a symbol of openness and unity as well as an investment in operational efficiency, local economy and development, and sustainability. DOWSIL™ Silicones for structural and insulating glazing contributed to the attainment of three demanding sustainability standards: LEED, LEED v4 and SNBS.
Carbon itself is a vital element of everybody’s DNA and without carbon, life on earth would not be possible.
Conversely, if we emit significantly more carbon in the form of carbon dioxide (CO2) than our planet can absorb, at a certain point, we will become extinct. To keep the balance is not the responsibility of any one individual; everybody has an obligation to actively contribute. Whilst cost control is important, the price we would be forced to pay for not managing carbon emissions is unthinkable.
There are legally binding targets for the reduction of net greenhouse gas emissions around the globe. In particular, the European Union is targeting a 55% reduction by 2030 and climate neutrality by 2050. The UK is targeting net zero emissions by 2050 including commitments to reduce emissions in 2035 by at least 78%, (compared to the 1990 levels). These targets cascade down to our construction value chain where our contribution represents a big opportunity.
Global share of buildings and construction final energy and emissions, 20191
Buildings make a significant contribution to global warming with about 39%* of carbon dioxide emissions, of which about 11% come from embodied carbon, so mostly construction materials used and the other approximately 28% is generated during building operation, predominantly coming from the building’s energy consumption due to heating/cooling, lighting, cooking, water heating, etc.…
A well-known source of CO2 emissions is fossil fuel combustion. So, looking at the building space, it is no surprise that construction material production, transportation, installation and energy generation during building operation, especially including the usage of fossil fuels, represents quite a significant level of CO2 or embodied carbon. A holistic view of the overall design and life cycle of a building or a façade is important. Building materials used in a façade design are sometimes overlooked when they also deserve equally important consideration together with their durability, circularity, recycling and of course, carbon footprint.
Carbon emissions and building operations
Innovation and new applications for existing technologies continue to emerge from the industry’s rapidly growing experience and knowledge for the mitigation of operational emissions. Building-integrated photovoltaics (BIPV), for example, are increasingly selected for roofs, skylights and facades for both new and remedial projects. Whether BIPV is chosen as a principal or ancillary source of electrical power, confidence and reliability in system durability and longevity is critical with such systems expected to operate safely and efficiently for the duration of the other façade or roof components, typically exceeding the 25–30-year lifetime of conventional PV modules. The more exposed elements of PV modules and laminates can be afforded high levels of protection and safety thanks to the use of proven silicone coatings and sealants. For example, DOWSIL™ 895 Structural Glazing Sealant securely bonds frames and junction boxes to PV laminates and has proven stability and durability in all environmental conditions whilst offering excellent performance in demanding applications such as structurally glazed facades. Two-component DOWSIL™ 993 Structural Glazing Sealant is used for rail bonding of frameless laminates enabling secure fixing and seamless photovoltaic facades.
It starts with the design
The carbon footprint of a building starts with its overall design, its functional requirements and how we can successfully integrate high-performance materials, whilst considering both embodied and operational carbon emissions. Pure glass façade designs are structurally bonded and depending on the type of design and area-specific requirements, energy efficiency can be enhanced. Structural bonding can also contribute to system rigidity in specific areas of the façade and therefore help to save potential additional material in the frame which can lead to a reduced final embodied carbon footprint. Different design options are available, from toggle systems to 4-sided structurally glazed systems.
Carbon emissions and construction materials
Using low carbon or carbon neutral materials is a great thing, because concrete, glass, aluminium and other components with a potentially reduced carbon footprint can also contribute. The challenge is that at the moment, there are not that many materials with a lower carbon footprint available.
It is fair to say that the European Green Deal will require more consideration to be given to how buildings of the future will be constructed, which materials are selected and their ease of removal, salvage and their reclaim potential. Interest is growing in renewable solutions with inbuilt lower embodied carbon, such as structural timber or timber framing, which can deliver systems with similar strength and as appealing aesthetics as conventional aluminium systems, yet with improved thermal properties and embodied carbon at a lower weight.
The use of timber construction has historically been limited to low to mid-rise construction due to performance and durability concerns such as moisture or fire resistance. Dow has developed silicon-based hydrophobizers which can help accelerate the adoption of timber construction in higher-performing structures. Dow’s water-based impregnation solutions, which are tailor-made to suit specific wood species, enable the required durability to be reached without impairing aesthetics or compromising the timber’s recyclability.
In parallel, Dow is evaluating the possibilities of direct wood bonding and the performance of silicone structural glazing sealants (SSG) in particular. It is much easier to machine and adapt timber for increased creativity or performance in frame design than with extruded aluminium profiles. The addition of an SSG solution would serve to further enhance its sustainability credentials. Finally, Dow also develops solutions for structural timber to improve fire resistance. Please contact us for further details.
Packaging – minimizing carbon footprint
Performance and sustainability are not only coming from the product inside the packaging! We are working with our packaging suppliers for the production and supply of standard sealant cartridges that will use 80% recycled plastic resin pellets. This change is another example of our strong commitment towards sustainability and our ongoing efforts to minimize our environmental footprint, while also helping customers to achieve circularity and meet their sustainability goals.
Impacting carbon footprint with durability and long-term performance
The longer facades last and the less repair or refurbishment that is required, the higher the impact on the long-term carbon footprint, which offsets the emissions incurred during production.
How long is a typical life cycle of a façade? One of the key elements is the quality and the longevity of the different components and materials used. For sealants in structural glazing designs, typically silicones are the material of choice. The European Technical Approval Guideline (ETAG 002) refers to an average lifetime of a façade of 25 years although in reality, facades last much longer than that. Structural glazing designs were pioneered in the mid-1960s, early 1970s with 2-sided structurally glazed designs. 4-sided structural glazing started a little later.
As the glazing of its almost 25-year-old façade at the IFT-Rosenheim Window Test Institute needed replacement to comply with current energy efficiency requirements, Dow took the opportunity to assess the performance of the bonding sealants after 25 years of work-life, combining climatic, dynamic and permanent loads. The sealants have been re-tested according to stringent test procedures for structural glazing silicones (ETAG 002). The outcome confirmed that the aged sealants still fulfil the requirements and could function for at least another 25 years, hence a 50+ year longevity projection. Even a specially simulated 50 years of service life test combining sealant aging and joint stress and movement at the same time proved that it would last more than 50 years.
In addition, the first 4-sided structurally glazed building is still in operation, based in Detroit using Dow Silicones and is celebrating in 2021 its 50 years of service life. These projects are actually a great testimonial for this technology and a proof of the long-term durability, which can help contribute to long-lasting facades.
Longevity and end-of life carbon balance
In a study commissioned by the Global Silicones Council titled Silicon-Chemistry Carbon Balance², various applications have been examined. The average benefits of a silicone until end of life have been assessed to be about 9 times higher versus the carbon dioxide emissions released during production. Applications using silicones in insulating glass even indicated a more than 27 times higher benefit.
Not only from a performance perspective, but also from a carbon balance perspective over the whole lifetime, technology choice is key to benefit from significant carbon savings.
The building environment – green and sustainable building certifications
Various green and sustainable building certifications are available globally with LEED, SGBC, BREEAM and DGNB amongst the most notable, which focus on reducing both operational and lower embodied carbon. The US Green Building Council (USGBC) recently produced the next generation LEED v4.1 standard for green building design, construction, operations and performance. This highlights that such certifications are encompassing more and more sustainability aspects which will likely need to be underpinned with low or carbon neutral product offerings that can be integrated into building designs for lower embodied carbon as well as reduced energy consumption. This is notwithstanding the ongoing requirements for building safety, design and durability. In addition, whilst a significant part of a building’s lifetime carbon print is locked into the materials used in a structure, these embodied emissions are currently unregulated. However, Building Life Cycle Assessments (LCAs) that evaluate the potential environmental impact of different processes and substances in conjunction with external EPDs (Environmental Product Declarations) are set to become the only reliable way to appraise the sustainability of a building. That said, commitment of suppliers to the social responsibilities of environmental, social and governance is of equal importance.
PAS 2060 verified carbon neutrality – a journey and a commitment
Product embodied carbon is primarily generated during production coming from energy consumptions using fossil fuels and waste. Various actions can be taken to offset the generated emissions. Two key elements are the continuous reduction of fossil fuels by using renewable energy (e.g., power coming from solar, water, wind, etc.) and, equally important, the ability to build additional natural sources absorbing the carbon dioxide produced (e.g., forestation, plantation, etc.). In reality, this journey has a much broader scope as social aspects come hand-in-hand with climate change, where efforts and investments need to be undertaken to address the impact on the economy, impact on society adopting climatic change as well as governance aspects. Therefore, Environmental, Social and Governance (ESG) are the key aspects to be considered when considering carbon emissions and carbon reduction. This is a journey which needs strong commitment. Returning to the indication that about 11% of the carbon equation are generated by building materials, it requires a huge and continuous effort of material companies to continually reduce levels of embodied carbon AND this requires a significant contribution and investment into Environmental, Social and Governance (ESG) – the “ESG carbon”.
Carbon neutrality it is not about buying offsets, it is a journey and a commitment towards continuously reducing material, hence the effect of the production carbon footprint. This does not happen overnight.
Verified and credible carbon neutrality claims are needed to avoid the negative perception of “pure green washing”.
The British Standard Institution with its PAS 2060 standard “Verified Carbon Neutrality” provides guidance on how to quantify, calculate, reduce and offset GHG emissions. With its international recognition and reputation, it helps build market confidence and trust. Annual audits contribute to continuous progress in the journey of reducing and offsetting emissions. A key difference is that offsetting using certified credits emphasizes and requires the support of climate finance projects with the aim of adding social and environmental value. The PAS 2060 is an internationally recognized standard which includes an “ambitious commitment to climate action”.
First Carbon Neutral Silicones High-Performance Facades
Dow High-Performance Building Facade will be introducing the first-ever PAS 2060 certified LOW CARBON silicone by end of 2021. This is a huge development and a revolutionary change that is strengthened by Dow’s environmental, social and governance (ESG) efforts, which is having a positive impact on the environment and the well-being of local communities. Our silicone materials already provide proven performance and durability in excess of 50 years, that is progressively impacting the carbon balance over the whole lifetime of a building in multiple applications. The introduction of carbon-neutral silicone materials will bring a completely new dimension to this technology offer, with externally audited carbon emission (CO2) certificates which will be provided with a complete life cycle analysis and contribute toward green building certification. Available anywhere in the world, customers can get this low carbon range for façades on a project-specific basis. It includes silicones for structural glazing, insulating glazing and weatherproofing.
Key benefits are:
- Individual project specific carbon neutral certificate – PAS 2060 with external EPDs
- Contribution to achieving regional and global targets for CO2 reduction
- Green Building Certification – supports getting additional points for LEEDS, SGBC, etc.
- Enhanced circularity with long-term durable structural glazing silicone: > 50 YEARS of performance, for enhanced building life cycle
- Reduced carbon footprint through smart structural glazing designs
Silicone is a powerful enabling technology that is set to contribute to an evolution in curtain wall designs for a reduced carbon footprint. Looking globally at the huge numbers of different captive façade systems, structural glazing designs can help enhance energy performance, which can positively impact the carbon balance when looking to reduce the operational carbon footprint over the lifetime of a building. Moving forward, cross-disciplinary industry collaboration will further accelerate the adoption of fully integrated designs which will play an important role in the ongoing development of low carbon solutions.
The ability of companies to bring to market truly low or carbon-neutral products is one measure of corporate sustainability. Specifiers seeking products for designs or systems will seek authenticity backed up with genuine data or credentials that are underpinned by exacting certifications.
Dow – silicone reduced carbon footprint
Dow’s lower carbon footprint for silicon metal production at Breu Branco site in Pará, located in the Amazon Rainforest of Brazil, is a competitive advantage for Dow. The manufacturing complex plays a critical role in Dow’s integrated global supply chain, providing a reliable and cost-competitive supply of silicon metal to manufacture high-value silicone products to serve our customers in diversified markets, including high-performance buildings.
At Breu Branco site, Dow uses more than 80% renewable energy, 100% audited woodchips and mineral sources, and 100% charcoal from FSC certified forest. We have invested millions of dollars in the Breu Branco site to make it safer and more efficient and will continue to invest strategically. This is another significant step on a challenging journey, but one that enables us to make a strong contribution to reforestation, sustainable forest management and protection of the native rainforest and its biodiversity.
With its ambitious 2025 Sustainability Goals, Dow collaborates with like-minded partners to help lead the transition to a sustainable planet, society and business environment. Our journey has evolved from focusing on operational efficiency (our footprint), to product solutions and world challenges (our handprint), to recognizing that only through collaboration can we accelerate our positive impact (blueprint thinking). Sustainability is not optional.
Visit the Dow showcase for innovation and performance-enhancing technologies for sustainable and modern building design at www.dow.com/buildingscienceconnect
1Adopted from IEA (2019a) World Energy Statistics and Balances
Author: Markus Plettau, Global Marketing Manager, Dow Façade High Performance Building
Markus Plettau is the global marketing manager for High-Performance Building Façade emphasizing market-based, sustainable and high-performance innovations. Based in Wiesbaden, Germany, he is tasked with developing product and system solutions for building envelopes that meet and exceed industry requirements and trends for energy-efficient, sustainable, safe and durable facades.