Sustainable Building Materials for UK Projects

The choice of materials is pivotal in any building project. The performance, life cycle and impact of materials used in a building project are critical. Sustainability is now a greater concern for most designers, contractors and clients as embodied energy or the carbon footprint of construction materials increase in significance. This paper provides information on some of the available materials and questions to consider when making a choice.

What Constitutes a Sustainable Material?

Although there are no definite rules, a material can be considered sustainable if it has a low environmental burden at each of the life cycle stages. The use of embodied energy to manufacture a building material is now a key consideration in material selection. Durability is equally important, as a material that is durable will reduce the impact of ongoing replacement.

Sourcing is equally important. Use of local materials reduces the carbon footprint of transporting the material and also ensures that the supply chain is managed responsibly, including no negative impact on the ecosystem and the community.

Timber and Engineered Wood

Growing trees to harvest to make timber are perhaps the easiest way to create a low-carbon building structure. Responsibly sourced timber can be used for a variety of purposes including framing, cladding and joinery. Engineered wood products, cross-laminated timber and glued-laminated timber, allow wood to be used for larger and taller structures.

Good detailing is important. Timber must be protected from persistent moisture. Fire performance, acoustic separation and long-term durability must be considered. When these are integrated into the design at an early stage, timber construction is fast to erect, light to transport and pleasant to occupy.

Recycled & Reclaimed Materials

The impact of extracting new materials can be eliminated by reusing materials. Reclaimed bricks, slates, beams and structural steel can be used in a new application where their quality and performance are suitable. Other recycled materials include fibrous insulation and aggregates from waste.

There are many practical challenges. Reclaimed materials may need to be tested to determine if they comply with the latest standards, and they may not always be available. Planning early and allowing additional time during the procurement phase can help.

Natural Insulation

Natural materials, such as sheep wool and wood fibre, can be used as insulation. Other natural materials, such as hemp, are also vapour permeable, which is helpful for managing moisture in older, less air-tight buildings.

It is important to verify the performance of natural insulation for each project. It is also important to ensure that project teams are familiar with each product and the correct methods of use. Used properly, natural insulation reduces the environmental impact of a project and improves thermal and acoustic performance.

Hempcrete and Straw

Hempcrete is a lightweight infill that is not load-bearing and requires a structural frame. It is made of hemp shiv and a lime binder. Straw bales can also be used as infill, and are now often sold in prefabricated panels. Both of these materials are renewable and offer good insulation values. Designers need to be comfortable working with different construction sequencing and drying times.

Lime and Low-Carbon Binders

In the UK, lime mortars and plasters have been used in masonry and timber construction. In traditional buildings, hard, low-permeability cement plasters can trap water and lead to decay of masonry. For new construction, cement and concrete can be replaced with less impactful alternatives.

Design for Longevity and Reuse

Permanent adhesives should be avoided in favour of mechanical fasteners. Standard or modular sizes should be used in the construction to facilitate removal and reuse. A simple, well-detailed, building can often be more sustainable than a complex, quickly-outlived building.

Questions to Ask When Specifying

From where does the material come? How far does it travel? What is it composed of? Are there harmful ingredients? For how long will it function? What maintenance will it need? Can it be reused and recycled? Does it perform for fire, structure, thermal comfort and moisture?

Working with the Whole Team

For successful sustainable material choices, designers, contractors and suppliers must communicate and agree early on. Unfamiliar material choices may need different sequencing, skills and storage.

Sustainability in construction is largely about trade-offs and experience, and not about exact numbers. With consideration for full life-cycle of a material, projects in the UK can positively impact the environment by delivering sustainable and high-performing built environments that are long lasting.