Embodied carbon – the emissions produced over a product’s entire lifecycle – is a growing concern for construction stakeholders. With carbon-intensive materials accounting for 11% of all operational greenhouse gases, reducing embodied carbon is a priority for architects & designers, manufacturers, and construction professionals.
To do this, leaders need to understand newer green approaches and balance their pros and cons.
Rammed Earth
A descendant of ancient construction techniques like adobe, rammed earth is a building material that’s made by compacting (or “ramming”) moistened subsoil into place between temporary formwork panels. When it dries, the walls are dense and hard. It’s an ancient style of building, associated with arid regions, and there are plenty of old rammed earth structures still standing around the world.
It’s not as common as concrete, but it’s becoming increasingly popular. Builders in the southwestern United States have become proficient at it, and the homes they build are very attractive and livable. But outside that region, it will take more effort to get a construction loan, mortgage or home insurance for a rammed earth building.
Stabilized rammed earth walls contain much less cement than bricks or concrete, between 5 and 8 percent. This means that they have less embodied carbon, and builders can substitute the cement with alternative binders, such as natural pozzolans or blast-furnace slag. In addition, the soil for rammed earth can be dug locally, reducing transportation requirements and CO2 emissions.
The walls are also very energy efficient, because they have high thermal mass and can be insulated. A well-designed rammed earth house, with south-facing windows in the winter and overhangs to shield them in summer, should require only one-third as much heating as a conventional home, saving on energy bills.
Wood
Wood is an abundant natural resource that can be easily recycled and reused. As a building material, it adds beauty, warmth, and a feeling of comfort to a home. It is a great choice for anyone concerned about climate change and wants to make a positive impact on the environment.
The main greenhouse gas (GHG) from wood is carbon dioxide, which is released when the timber burns or decomposes. However, it is important to note that a wood product’s GHG footprint can be offset by the HWP sink impact. HWPs are a significant component of biogenic greenhouse gas flows, and incorporating them into life-cycle assessments is necessary to complete a full analysis of a forest product’s GHG footprint.
Using wood products instead of concrete and steel in construction can displace fossil emissions. However, it is important to understand that displacement factors are based on counterfactual analyses and may overstate the avoided emissions from increased wood use.
The use of wood in construction can also generate other GHGs during its life cycle. This is primarily because of the carbon dioxide that is released during the harvesting, transport, and combustion of wood for energy production. This additional carbon dioxide is not included in the typical GHG calculations for wood-based products because it does not enter the atmosphere directly from a harvested forest.
Concrete
Concrete is the second most widely used material on Earth – after water. It is also one of the world’s leading carbon dioxide emitters, with production accounting for 8% of the global industry’s emissions. This figure is likely to rise, as the concrete and cement industry is growing faster than any other industrial sector in the developing world.
The calcination process used to create Portland cement, the most common form of concrete, is by far the most energy-intensive aspect of its production. It uses up to 3.5 million barrels of fuel oil each year, and it is this energy demand that is driving its rising emissions. The concrete industry can reduce its emissions by using alternative blends of materials – but these are generally more expensive. It is also possible to prevent the carbon released during kiln heating from entering the atmosphere by using carbon capture and sequestration (CCS), but this technology is still relatively expensive, which limits its adoption in the concrete industry.
In the future, concrete and cement companies will need to focus on decarbonization strategies that reconcile societal needs and ecological imperatives. This will require a shift away from the use of fossil fuels in kiln heating processes and a move towards renewable electricity sources. They will also need to embrace sustainable production methods such as the use of recycled aggregates, which reduces the demand for natural resources.
Insulation
Insulation can significantly lower energy costs in both new and existing buildings, and also reduce carbon emissions by reducing the amount of energy required for heating and cooling. In fact, a single home or building that is adequately insulated can save up to 30% of its energy usage, resulting in substantial savings on both electricity and heating and cooling bills. This reduced reliance on energy consumption lessens the demand for fossil fuels, mitigating climate change.
Furthermore, if the insulation is made of recycled materials such as cellulose or mineral wool it can also decrease a building’s embodied carbon footprint. Embodied carbon is the total energy it takes to produce a building material (from raw material extraction to manufacturing and transportation) and is an indicator of its potential impact on climate change. For instance, cellulose insulation is made from up to 85% recycled paper and diverts tons of waste from landfills where it would otherwise decompose and release carbon into the atmosphere. It also takes 64 times less embodied energy to produce than foam insulation and 10 times less than fiberglass.
Insulation has the potential to be one of the most sustainable construction materials available. As innovation continues, it can be expected that new and improved insulation will provide higher levels of sustainability in terms of both energy efficiency and environmental impact.