The Earth’s climate has changed throughout history. Most of the climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives. The current warming trend is of particular significance because most of it is extremely likely (greater than 95% probability) to be the result of human activity since the mid-20th century and proceeding at a rate that is unprecedented over decades.
Whatever the truth about the proportion of global warming caused by man and compared to natural causes, there is no doubt that we are burning more fossil fuels and causing more pollution than ever before. This impacts climate change and causes environmental degradation. Most fossil fuels are now imported; leading to dependency, so there are very sensible economic and political cases for reducing fossil fuel consumption.
Buildings account for about half of the total fuel burn and commercial buildings account half of that for. The reduction of this figure is probably easiest on big buildings. Unless buildings become more efficient and use clean energy sources, there is no way the political target of a Net Zero Emissions by 2070 will be met.
What Are Low-Carbon Buildings?
Low-Carbon Buildings (LCBs) are specifically engineered with GHG reduction in mind. So by definition, an LCB is a building that emits significantly less GHG than regular buildings. Carbon dioxide equivalence (CO2e) provides a simple metric for determining the environmental performance of buildings, including both embodied emissions and operating emissions.
There is presently no emissions threshold under which a building would qualify as an LCB. But to be genuinely “Climate Change neutral”, an LCB would have to achieve at least 80% GHG reduction compared to traditional buildings. According to the “Stern Review on the Economics of Climate Change”, emissions would have to be reduced by 80% compared to current levels in order not to exceed the Earth’s natural capacity to remove GHG from the atmosphere. By comparison, a regular building releases about 5,000 kgCO2e/m2 during its entire lifetime (though it varies a lot, depending on the project type and where it is located).
It is interesting to note that on a per-capita basis, India is one of the lowest Greenhouse Gas (GHG) emitters in the world – 1.91 tonnes of CO2 equivalent per capita. However, India is highly vulnerable to climate change, and has a strong interest in having a fair and equitable global agreement for minimizing the risk of climate change. Not due to anyone country alone, climate change is largely due to the historical emissions of the developed countries, India stands ready to be a part of the solution.
Opportunities for Low-Carbon Buildings
As one of the largest sources of carbon emissions, buildings represent a significant target of opportunity for carbon reductions. The Intergovernmental Panel on Climate Change (IPCC) has identified buildings as the sector with the greatest potential for carbon reductions, particularly because reductions that result from improved building performance also yield substantial economic benefits.
The World Business Council for Sustainable Development has concluded that the energy use of buildings worldwide could be reduced by 60% by 2050 using existing technologies. McKinsey Consulting has identified the building sector as the most cost-effective target for carbon abatement.
Efficient Building Design
One of the best opportunities (also most cost-effective) for large-scale reductions in carbon dioxide emissions on a national and global scale is to have more efficient building design. Thus, emphasis on integrated building design for the full life cycle of a building can lead to dramatic improvements in building performance. It requires incorporating systems thinking at the conceptual design stage, taking into account climate-specific factors and regional climate. Decisions about building orientation, façades, heating and cooling strategies, and glazing ratios, which must be made early in the design process, are crucial factors in the final energy performance of a building.
Use of Simulations as Design Tools
Several tools have been developed in the last few years to assist architects and engineers by providing architects with rapid feedback on environmental performance at early stages of design. Simulation results can be used for efficient master planning, building planning, façade design and MEP systems selection. It also works like a decision making tool for owners and project teams.
The choice of materials for a building cannot only determine the embodied carbon of a building, but also has implications for the carbon emissions from building operations, through thermal mass and improved day-lighting. Appropriate building materials can moderate diurnal temperature swings or help to distribute daylight deeper into interior spaces. These help reducing heat loads and optimize building systems resulting in lower capital and operational costs.
While a building can be LCB by reducing its carbon emissions, it needs to have zero emissions in its construction, operation and embodied energy, to be truly carbon neutral.
How Buildings Achieve Zero Net Operating Emissions
It is possible for buildings to achieve zero net operating emissions. There are already a number of projects worldwide that achieve this. New and existing buildings are taking steps towards becoming carbon neutral now by including a range of initiatives and technologies:
- Climate responsive design
- Efficient Master Planning
- Efficient design of building façade
- Efficient appliances and light fittings
- Optimizing or upgrading HVAC systems
- On-site renewable energy generation
- Purchasing green power
How Buildings Can Go Carbon Neutral, Including Embodied Energy
Embodied energy is all the energy required to construct a building. This can include energy required for producing and transporting building materials, on-site processes for constructing the building, as well as demolition of the building when time comes.
There are some things that can be done now to reduce the embodied energy in buildings, such as:
- Measuring the embodied energy
- Re-using and reducing materials
- Re-using and refurbishing existing buildings
- Considering how the building material is transported
Transportation of building materials
Building products have to be transported from their point of origin to the construction site. The energy used for this activity is generally included in the embodied energy of products. This energy, while small compared to the energy used in the manufacture of the product, can be reduced by:
- Changing the mode of transportation, e.g. using train or ship freight rather than trucks
- Using a fuel source with less environmental impact for transporting materials, e.g. hybrid vehicles or LPG;
Smart route planning, where trips to several destinations in close proximity of each other are combined.
Challenges for Low-Carbon Buildings
The Role of Engineers
Engineers play a crucial in designing more sustainable buildings and are often involved too late in the design process to make all of the necessary decisions. Many key decisions, such as building orientation, building massing, glazing ratio, and the overall form of the building are made in the earliest design stages. Once these critical decisions have been made, engineers have to attempt optimizing a poor design, but it is difficult at that point to achieve a low-carbon design.
The challenge is to integrate engineering analysis in a way that provides rapid feedback to architects and the rest of the design team early in the process. For this, engineers must be trained as designers, so they can propose multiple solutions to open-ended problems. In short, the design of high-performance buildings requires integrated systems thinking beginning in the earliest conceptual design stage. To ensure that engineers with the necessary skills are available, more of them must be trained in building science and sustainable design.
The buildings sector possesses a significant opportunity to achieve cost effective carbon reductions. An intensive emphasis on conceptual design and life-cycle thinking will be necessary to advance the field, reduce carbon emissions, and train a new generation of engineers. Integrated Design Approach is the key and the way forward where Architects, Engineers and Sustainability experts need to collaborate towards achieving low-carbon built environment.
Ashish K Jain is the Partner of AEON Integrated Building Design Consultants LLP. He is an MPM, FAAPM, AIID, LEED AP, IGBC AP.