🕑 Reading time: 1 minute
The building construction sector is a significant contributor to the overall global carbon emissions. This includes the emissions during the construction phase as well as throughout the building's operational life.
The construction phase comprises emissions due to equipment, heavy machinery, and the vehicles used for transportation of the building materials. During the operational life, electricity, power requirements, and maintenance are a big part of the building's carbon emissions. Moreover, buildings contribute to carbon emissions, even when they are demolished.
Almost half of the greenhouse gas emissions are generated from the urban construction sector. Therefore, it is of utmost importance to consider the construction of buildings with minimal carbon footprint. The Pixel building in Melbourne, Australia, is one such epitome of sustainable construction.
About The Pixel Building
The carbon-neutral Pixel building was constructed in July 2010. The building was developed to support the changing business practices and provide a dynamic work environment.
The idea for the project was conceived to create a structure capable of minimizing the carbon emissions generated during and after its life span.
The building will offset all of the carbon used in its construction over time and generate energy back to the grid.
How is the Pixel building keeping a check on carbon emissions?
The Pixel building has managed to keep a check on its carbon emissions, which is significantly less than that of ordinary buildings. The building has secured the highest LEED (Leadership in Energy and Environmental Design) and BREEAM (Building Research Establishment Environmental Assessment Method) ratings. These rating systems are highly systematic and reliable. A brief explanation of the same is given in the FAQ section at the bottom of the article.
1. Photovoltaics and Wind Turbines
The roof of the Pixel building is installed with wind turbines and solar panels. The panels with solar tracking system can generate 6.3 kW of electricity, while the wind turbines have an installed capacity of 5 kW. The building has reduced dependence on other external sources of energy and is quite self-sufficient. It fulfills most of its energy requirements without affecting the environment.
2. Rainwater Harvesting
Rainwater harvesting is commonly used as an additional source of water in many buildings. The Pixel building is also equipped with special tanks to collect and treat the stored water to be distributed across washrooms and other areas. The leftover wastewater (also known as Grey wastewater) is used for watering the plants.
3. Eco-Friendly Refrigerants
Refrigerants such as CFCs (chlorofluorocarbons), hydro-fluorocarbons, and halons form an integral part of various cooling systems such as air conditioners and refrigerators. These refrigerants are infamous for their adverse effects on the ozone layer of the atmosphere. To tackle this, the Pixel building does not depend on air conditioners and utilizes Ammonia refrigerant. This ammonia refrigerant has zero impact on the environment as it does not deplete the ozone layer and is a reliable substitute for CFCs.
Cement is a fundamental element of any concrete mix. Its production includes the manufacturing of clinker by calcination in large kilns at temperatures as high as 1450°C. This process alone generates a considerable amount of carbon emissions; therefore, cement is responsible for around 8% of the world's CO2 emissions.
Therefore, the Pixel building utilized a unique concrete mix called 'Pixelcrete'. With nearly 60% less cement than a traditional concrete mix, it has helped in significantly reducing the building's carbon footprint. Besides, the aggregate used in this mix was recycled.
5. Unique Air Conditioning System
The Pixel building is unique in yet another aspect. For instance, it does not have several fans on each floor and instead has only two fans—one for the supply of fresh air, and the second one for releasing the fully exhausted air out of the building.
The air entering the building from the outside is heated or cooled, as per the requirement, by a gas-fired ammonia absorption heat pump. Absorption heat pumps are beneficial in situations where both heating and cooling is required. In an ammonia heat pump, ammonia acts as the refrigerant when cooler air is needed, while water acts as an absorption medium by giving out substantial heat when warmer air is required.
The building features thermally active floors with vents responsible for circulating the pre-conditioned air evenly on each floor. The individual exhaust vents located in the ceilings carry the exhausted air to the main exhaust fan. In this manner, fresh and conditioned air is circulated throughout the building without affecting the environment.
6. Vacuum Flush Toilets
A share of the treated rainwater is sent to the vacuum flush toilets in the building. These vacuum flush toilets use air suction to remove fecal waste and minimize water usage. Although, setting up a vacuum flushing system requires some level of expertise, it is an excellent initiative towards a greener outlook.
7. Anaerobic Digester
The roof of the Pixel building also has a small anaerobic digester that receives the waste from the vacuum flush and effectively produces biogas from it. This sewage then goes directly towards the sewer pipelines. Overall, this digester ensures that no form of energy remains unused from within the building.
8. Reduced Energy Demand
The Pixel building was constructed with a focus on carbon balance rather than energy and is therefore energy-positive but carbon neutral. Its design incorporates energy-efficient components in the facade and services to minimize electricity required for lighting, heating, cooling, and ventilation.
Apart from the entire building using only two fans, it also utilizes LED lights for non-office areas, an external shading system to reduce solar thermal loads, and an individually addressable dimming system.
Grey water waste is the waste water generated from any building’s occupants, other than the fecal waste. All other uses of water such as washing hands, washing utensils, bathing etc. constitute grey water waste. This waste water is not as toxic as the sewage waste (black water waste) and requires little to no chemical treatment. Sometimes, this water is used for other purposes such as watering the garden or plants, which is also the case in the Pixel building. This helps in reducing the waste water generation as well as save the extra water which would otherwise be used for watering plants.
Often when buildings reach the end of their service lives or there are certain building violations, demolition of the buildings are carried out. This process requires fuel operated heavy equipment which generates considerable amounts of CO2. Moreover, a major part of the demolished building is not reusable and is dumped away into landfills or some other waste treatment is done. This again aggravates the problem of carbon emissions and waste production.
LEED stands for Leadership in Energy and Environmental Design. It is a world famous green building rating system. Ever since the concept of green buildings was realized, a benchmark for their effectiveness was required. The LEED credit categories which is illustrated below, shows the parameters on which the building is rated. A building can score a maximum of 110 points on this rating system and the Pixel building has an outstanding score of 105 points.
BREEAM stands for Building Research Establishment Environmental Assessment Method which was launched long back by the Building Research Establishment of the UK. A few criteria which this system takes into consideration are : Ecology, Pollution, Waste, Energy, Management, Water consumption, Health and Well being, Efficiency, Materials and Transport. The rating scale that the BREEAM follows has six rating benchmarks which are shown in the illustration below.
Low Carbon Concrete and Its Advantages
How can we reduce the carbon footprint in the Construction Sector?