Can Buildings Store Carbon?

When we think about the relationship between buildings and climate change, the conversation often focuses on energy. How efficiently a building is heated, how well it is insulated and whether renewable energy can reduce its reliance on the grid all have an important role to play.

But there is another part of the picture that is receiving increasing attention: what we build with.

Some construction materials begin their lives by absorbing carbon dioxide from the atmosphere. When these products are incorporated into a structure, some of that captured carbon can remain stored within them for decades.

This is known as biogenic carbon storage, and it is changing the way we think about the environmental impact of what we build with.

From forests to buildings

Timber is one of the clearest examples.

Trees absorb carbon dioxide as they grow through photosynthesis, storing carbon within their biomass. When sustainably sourced timber is turned into structural components, flooring, doors or other building products, that carbon remains stored throughout its useful life.

The UK’s 2025 Timber in Construction Roadmap recognises this potential. It states that sustainably sourced timber products can act as carbon stores for the duration of their use, with that storage potentially continuing when timber is reused or recycled.

The figures are particularly interesting. The Government estimates that carbon storage at an individual building level is approximately 50% higher in timber-framed homes than in masonry homes, while for larger structures using engineered timber such as cross-laminated timber (CLT), storage can be up to 400% higher than when concrete is used.

That doesn’t mean timber automatically makes a development carbon neutral. Its production, transportation, treatment and eventual disposal all contribute to its overall environmental impact. But it demonstrates an important shift in thinking: the materials within a building can hold carbon, as well as generate emissions.

Beyond timber

The concept isn’t limited to structural timber.

Hemp-based products, including hemp-lime, use rapidly renewable plant material that has absorbed carbon during growth. Straw can also be incorporated into construction, retaining some of the carbon captured by the crop while providing an alternative to more carbon-intensive products.

Other emerging applications include biochar, wood fibre and cellulose-based components, with researchers exploring how plant-derived products could be incorporated into insulation, wall systems and other parts of the building envelope.

This is becoming increasingly relevant as the industry looks beyond the energy used once a building is occupied. Embodied carbon accounts for emissions associated with the materials and products that make up a building, including their manufacture, transportation, maintenance and disposal.

As properties become more energy efficient, understanding their associated carbon impact becomes an increasingly important part of the wider picture.

Storage isn’t the whole story

There is, however, an important distinction to make: storing carbon doesn’t automatically make a product low-carbon, and a structure containing bio-based products isn’t automatically carbon-negative.

The full life cycle needs to be considered. Sustainable sourcing, manufacturing processes, transportation, durability, maintenance and what happens at the end of the building’s life can all affect its overall carbon impact.

This is one reason the Government’s Timber in Construction Roadmap places emphasis not only on increasing timber use, but also on whole-life carbon, sustainable sourcing, fire safety, durability and opportunities for reuse.

Reuse is particularly interesting. If a timber component can be removed from one structure and incorporated into another, the period for which that carbon remains stored can potentially be extended. Designing so that materials can be repaired, dismantled and reused could therefore become an increasingly important part of a more circular approach to construction.

A different way to build

The idea of carbon storage doesn’t mean every future build needs to be made entirely from timber, hemp or other biological resources. Different products have different properties, and the most appropriate solution will depend on the building, its location, structural requirements and how it will be used.

A timber frame could retain carbon captured by trees. Hemp-based insulation could store some of the carbon absorbed during the plant’s growth. Reused materials could extend that storage period further, while thoughtful design could make it easier to recover components at the end of a building’s life.

It then becomes part of a longer carbon cycle, rather than simply a final destination for raw materials.

The possibility of buildings storing carbon is still evolving, but it offers a fascinating new way to think about sustainable design: not simply reducing the impact of what we build, but considering how the buildings themselves could play a role in keeping carbon out of the atmosphere.