by Katherine Bruce
[TL;DR] The Living Building Challenge is a sustainability certification scheme that addresses some of the key issues of building construction and operation. The certification aims to encourage a regenerative building that positively contributes to its surroundings with minimal to net zero, water and energy consumption. To date, many projects are under four stories in height. This post explores how tall buildings in the Middle East can apply the net zero principles to improve their sustainability performance and ultimately contribute to improving the wellbeing of the occupants and surrounding residents.
The construction and operation of buildings is the largest energy consuming sector, contributing towards nearly 40% of our world’s annual energy demand .
In light of this, the World Green Building Council recently launched their ‘Advancing Net Zero Program’, which supports and accelerates the transition of buildings to become 100% net zero carbon by 2050. Buildings also have a significant impact on our health and wellbeing, considering that we spend around 90% of our time indoors. We need to use buildings as catalysts to improve our quality of life and reduce our environmental footprint.
A sustainability certification scheme that aims to tackle some of these issues is the ‘Living Building Challenge’ (LBC). Developed by the International Living Future Institute in 2006, the scheme is comprised of seven themes, known as petals. For a building to become fully certified, the project must achieve all of the criteria under these petals. Alternatively, the building can be petal certified if the project achieves at least one of the energy, water and materials petals. Examples of buildings certified include the Bulitt Center in Seattle (one of the world’s largest net positive energy buildings producing a surplus of 30% more energy than it demands) and the Google Office in Chicago, which achieved the materials petal through reductions in embodied energy and use of low toxic materials. However, to date, the majority of LBC projects are less than 4 stories in height.
Globally, there are around 41 certified LBC projects and 280 registered projects (Dec 2019). However, one area with a particularly low uptake of the certification is the Middle East. Buildings in this region are often exposed to extreme climatic conditions such sandstorms, temperatures above 40oC and humidity levels in excess of 80%. Hence the LBC framework is often seen as challenging to apply in these environments. In this region, tall buildings are a particular characteristic of city skylines (Dubai, Abu Dhabi, Doha, Kuwait), so it is crucial we look to improve their long-term sustainability.
Figure- Dubai Marina Skyline
In this post, we have examined a case study of a typical 60 story office building in the Middle East, what would be required to reach some of the LBC targets: net zero energy and water?
Let’s start with energy. Using the ASHARE Standard 90.1 as a baseline, and maximizing the application of passive and active measures available on the market, it was possible to reduce the case study building’s energy consumption by 55% (refer to figure below). Some measures included: fiber optic cables to capture daylight and reduce the electrical lighting demand, daylight responsive shading and glazing to reduce solar heat gain, and installation of PV to generate on-site energy. The building would also benefit from free-cooling during up to 60% of winter month hours.
Figure- Measures applied to reduce a tall building's energy consumption
Despite the passive and active measures, there is still a 45% energy gap to be closed through on-site energy generation. Installation of solar PV on the small roof area barely contributes to the huge energy demand of a tall building. Other technologies like building integrated photovoltaic (BIPV) have performance challenges, for example the angle of installation typically at 90o, hence not facing optimum sunlight and the lack of airflow leads to faster degradation.
The solar-hydrogen cycle is one potential solution for advancing on-site energy generation. Solar energy may be used to power the electrolysis of water to generate hydrogen. The hydrogen can then be stored and used to generate electricity. Scientists are investigating various catalysts to make this process more cost effective, but what is great about the solar-hydrogen cycle is that water is a by-product of this process. In water deprived areas like Dubai, coupling energy and water generation would have immense benefits.
Tall buildings should also look to capitalize on their large exposed surface area, and not only through integrating BIPV. A good example is in Hamburg, Germany where a building has installed a bio reactive façade used to harvest algae. Harvested algae can be used as biofuel, in food supplements, cosmetics, animal feed or fertilizer. As an energy generator, the process is not yet competitive with fossil fuels but is expected to improve as the technology matures.
Engineers are investigating other sources of on-site energy generation that will reduce a skyscraper’s reliance on the gird. Although technically not applicable under the current LBC criteria, micro nuclear reactors (MNRs) may play a key role in decentralized energy generation. An MNR will be around 3-4 stories in height, fitting neatly into the basement parking of a skyscraper. Due to the small size of an MNR, engineers report significantly reduced risks in comparison to the large nuclear power plants. Several firms are developing these reactors and one company named U-Battery is targeting 2025 for installation in a remote off-grid community in Canada. Now, obviously there are associated issues with nuclear waste and we are still several years from unlocking fusion reactions. However, if we need to drastically cut down are CO2 emissions, this may be one solution.
Another key element of the LBC framework is the water petal – 100% of water must be contained in a closed loop system. Going back to the case study building, water consumption in a building may be reduced by design (installation of low flow fixtures and drought resistant landscaping for example) and through water reuse (condensate, greywater and rainwater recycling). By installing these measures a skyscraper could reduce water consumption by 68% using the LEED calculator as a baseline (refer to figure below). However, what would be required to achieve a 100% closed loop process?
Figure - Measures applied to reduce a tall buildings water consumption
Treatment of blackwater (water from toilets) is typically processed through municipality water treatment systems. The TSE (treated sewage effluent) is restricted for irrigation requirements only due to its quality. In recent years, technology has been developed for the on-site treatment of blackwater. One example is the Aquacell system, which is not much larger than a car. Developers are also looking to tap into existing sewer networks in a process known as sewer mining. Collecting this water reduces the demand placed on municipality systems and also allows a consistent flow through on-site water treatment units.
Another source of water is fog. In the winter, coastal cities in the Middle East are often coated by a layer of fog in the early morning. Scientists are investigating ways to capture the condensate directly from the air. Using biomimicry design techniques, a material has been developed that mimics the structure of the desert beetle. Micro-sized grooves and a combination of hydrophilic and hydrophobic surfaces allow the beetle to capture water from the humidity of the air. The material could be applied on the facades of buildings to increase water generation at site.
Now for water consumption. Did you know that toilets are the highest water consuming fixtures in a building? The installation of waterless urinals is becoming wide spread in many projects in the region due to the water saving they can achieve. Hand basin water can also be used to directly fill the cistern of a toilet, reducing the cost of a dedicated a greywater system.
The majority of countries in the Middle East rely on energy intensive desalination for potable water. There are pockets of geothermal water sources in the region at 120oC, although not hot enough to generate electricity the temperatures are suitable for desalination through membrane distillation processes. As it stands, high cost is a limitation.
Finally, the materials petal. One of the criteria under this petal is for the project to offset its embodied emissions. The embodied energy of steel and cement alone contributes to almost half of our industrial CO2 emissions. And tall buildings have a significant footprint
The embodied emissions of the Burj Khalifa is around 4 tonnes of CO2 per m2, which is ten times higher than a traditional villa in the region.
Rather than look to replacing these materials, we should first consider how we can reduce our consumption. Several design strategies may be applied, such as designing components that serve the same purpose but use less by design. These include improving the manufacturing process of the materials to reduce yield losses, reusing metal components (for example steel piling can be used multiple times before being discarded) and designing for deconstruction to enable reuse of components.
We can even take a step further and use materials to generate the surroundings. Researchers at UCL have developed a bio-active concrete that mimics the bark of the tree. Under the right conditions (porosity, pH and temperature), the concrete allows mosses and lichens to propagate from spores in the air. Such natural biodiversity is self-sustaining, and so reduces maintenance costs and irrigation. Furthermore, plants help to remove pollution from the air.
To summarize, the LBC framework is challenging but not impossible for the region. There are clearly still cost and political barriers to overcome, but skyscrapers of the future will not only be efficient in design but also have the ability to generate energy and water and provide for their surroundings.