Natural Building Systems Limited                            SBE0010

Written evidence from Natural Building Systems Limited

Introduction and reasons for submitting evidence:

Natural Building Systems was established in 2019 with the purpose of researching and developing ultra-low-carbon alternatives to mainstream construction products and modular systems to promote a circular economy.

UK greenhouse gas emissions are 435.2MtCO2e, of which 24.9MtCO2e is embedded through new construction. The industry has been set the target of reducing emissions by 76% by 2050 (18.9MtCO2e). Currently UK building regulations focus exclusively on operational energy reductions. However, carbon emissions embedded in construction materials are far more consequential when considered in the context of grid decarbonisation and whole life cycle carbon. Indeed, some measures aimed at reducing operational energy have the unwanted effect of both front-loading carbon emissions and increasing the overall whole life cycle carbon impact of a building.

The technological challenge is a radical decarbonisation of construction materials. High energy bricks, steel and concrete need to be replaced with low carbon alternatives wherever possible.

More can be done to make low carbon alternative materials available. Engagement with approaches such as the RICS whole-life carbon assessment guidance may encourage broader acceptance, but government policy (both in planning and building regulations) needs to change to promote the adoption of high performing carbon sequestering materials such as straw, hemp, and timber. In particular, industrial hemp has huge potential as a construction material due to its exceptional hygrothermal characteristics and capacity to sequester 275% more carbon than forestry, straight away (rather than waiting decades to mature) and without competing with food supplies.

Novel bio-composites are now in development which allow these materials to be used with digital technologies and MMC, but barriers to entry include the high costs of product certification and regulations which discourage investment in farming and processing.

It takes over 50tCO2e to build an average UK house. When built using carbon sequestering products its carbon footprint reduces by 53tCO2e, resulting in negative-carbon housing.

The UK government has demanded the construction of up to 300,000 houses annually, yet construction of these houses using masonry and concrete would typically embed an additional 15MtCO2e. Construction of 100,000 houses using low carbon alternatives to mainstream construction products would save 5.3MtCO2e or 28% of the construction industry's target reduction.

In answer to specific questions:

Unfortunately, the CCC recommendation to increase the use of timber in construction is largely counteracted by revisions to the building regulations following the Grenfell disaster. But the focus on timber is in any case, far too narrow, since other biogenic materials offer better functionality and performance together with greater and more immediate carbon sequestration.

Materials which passively regulate indoor temperature and humidity such as wood-fibre and hemp bio-composite insulations can significantly reduce operational energy use and ‘up front’ embedded carbon.

The planning system and building regulations can and should play a role in encouraging the use of low carbon materials and sustainable design. Examples such as the draft GLA’s guidance on the circular economy and whole life-cycle carbon assessment are already promoting more sustainable development in London, by requiring early-stage development plans to anticipate future regulations.

If EPD’s were mandatory for all construction products, the building regulations could be revised to incorporate a rigorous application of EN15978, with a maximum permissible limit of embodied carbon relative to gross internal floor area.

May 2021