Most of us spend a large chunk of our lives in one building or another, but have you ever stopped to consider the greenhouse gases linked to the construction of these buildings?
One way to reduce greenhouse gases is the use of recycled and more environmentally friendly building materials.
The United Nations Environment Programme (UNEP) International Resource Panel has just published a recent report titled Resource Efficiency and Climate Change: Material Efficiency Strategies for a Low-Carbon Future. Commissioned by the G7 countries, it shows that natural resource extraction and processing account for more than 90 per cent of global biodiversity loss and water stress, and around half of global greenhouse gas emissions.
The findings point to opportunities to reduce these impacts through material efficiencies in homes and cars.
According to the Panel’s modelling, emissions from the material cycle of residential buildings in the G7 and China could be reduced by at least 80 per cent in 2050 through a series of material efficiency strategies.
A design with fewer or alternative materials, and more recycling of construction materials are among the most promising strategies, it says.
More concretely, the Panel’s modeling tells us that within the buildings and construction sector, we could reduce greenhouse gas emissions by 350 million tonnes in China; 270 million tonnes in India, and 170 million tonnes in G7 countries, between 2016 and 2060.
“Policy intervention from different angles is required to achieve these savings,” says the head of UNEP’s Cities Unit, Martina Otto.
“Policies can influence how people live, which materials they use and how they use them. Instruments such as taxation, zoning and land use regulation play a role, but so do consumer preferences and behaviour.Building codes and standards drive building performance and connect building design to policy. They can encourage or constrain material efficiency and circularity.”
According to the 2019 Global Status Report for Buildings and Construction, almost 40 per cent of energy-related greenhouse gas emissions are from the buildings and construction sector.
”In the buildings and construction sector, much attention was concentrated on ‘operational energy efficiency’, the energy used in buildings and which can be influenced by building design, insulation, passive solutions for heating and cooling, appliances and systems improvements as well as maintenance and usage,” says Otto. “But we also need to look at materials to reduce pressure on natural resources and ‘embodied carbon’.” Embodied carbon is the amount of carbon (CO2 or CO2 emission) to produce a material.
Building design and the use of recycled and alternative materials
In G7 countries, material efficiency strategies, including the use of recycled materials, could reduce greenhouse gas emissions in the material cycle of residential buildings by 80 to 100 per cent in 2050, the Panel’s report suggests. Potential reductions in China could amount to 80 to 100 per cent, and to 50 to 70 per cent in India in 2050.
“There are many different options. For example, sustainably managed and harvested timber has the potential to reduce greenhouse gas emissions by 1 to 8 per cent in 2050 in the G7,” says Otto. “There are also a variety of new products, for example from agricultural waste, that could help close loops towards circularity. Choices need to be locally appropriate and include sustainability considerations.
“Designing buildings using less material (savings of 8 to 10 per cent in 2050 in the G7, according to the Panel’s report) is another thing to look at, alongside passive cooling and heating and natural light to reduce operational energy at the same time.”
The consumption angle
Measures with the highest impact and lowest cost include getting greater use out of buildings for more hours per day and extending the lifetime of buildings (the Panel says up to 70 per cent savings could be achieved by 2050 in the G7).
Improved recycling could reduce greenhouse gases by 14 to 18 per cent in 2050 in the G7. Overall, cumulative savings in the period 2016–2050 from these strategies in the G7 would amount to 5 to 7 gigatonnes of CO2 equivalent, says the report.
Looking at the whole building life cycle, material efficiency strategies could reduce emissions in 2050 from the construction, operations and dismantling of homes by 35 to 40 per cent in the G7. Analogous savings could be up to 50 to 70 per cent in China and India.
“Virgin material taxation and removal of virgin resource subsidies should be key options for policymakers,” says Otto. The Global ABC Roadmaps 2020–2050 provide targets and timelines to achieve zero-emissions, efficient and resilient buildings and construction.
The world must immediately begin to deliver faster greenhouse gas emission cuts to keep global temperature rise to 1.5°C, says the November 2019 edition of UNEP’s Emissions Gap Report.
“To achieve this goal, we will need to use the full range of emission reduction options. We need progress in all sectors: energy, industry, agriculture, forestry, transportation and buildings, better integration across sectors, and urban planning and design to meet this target,” says Otto.