Building New Homes And Meeting Climate Targets

AIMCH recently concluded that using sustainably sourced timber panelised methods could transform housing delivery. Stewart Dalgarno, AIMCH Project Director explains more.

The end of the UN’s climate change conference COP26 marked the beginning of the hard work required to prevent global warming rising above 1.5C. For the UK to play its part in lowering emissions, the construction sector, which accounts for 47% of the country’s total carbon emissions, must accelerate the adoption of new sustainable ways of working across the built environment sector.

Advanced Industrialised Methods for the Construction of Homes (AIMCH) is a project I believe offers the housebuilding industry a way to continue to improve the sector’s environmental performance.

The challenges faced by AIMCH are not insurmountable, but we must acknowledge that it is concluding at a time when demand for high quality, energy efficient and affordable housing continues to grow. What excites me most about it though, is that the project could offer solutions to skills shortages, the ageing workforce and poor productivity – challenges not limited to the housing sector, while also responding to requirements to use sustainable materials and panelised offsite systems.

AIMCH's ambition is to use industrialisation to transform how we build our homes in the UK, leading to more homes that can be built quickly, viable and sustainably. If we get it right, I believe the AIMCH project will accelerate the delivery of the 120,000 new homes the UK needs each year, for an acceptable cost, compared to masonry-built homes and with at least 30% reduction in build times.

An integral part of the project has been the completion of a whole life carbon assessment of current building regulations over a 60-year design life, assessing four typical homes across masonry, open and closed panel timber methods. The report’s findings indicate five tonnes of embodied carbon saving, per four-bedroom home, when using timber construction compared to masonry, equivalent to 16,500 road mile emissions. The report also finds that aerated masonry blocks have half a tonne less carbon emissions at end of life than timber frame construction methods. The carbon sequestration benefits of timber have been used in the research, benefiting all construction methods, where elements of the build use timber, such as internal non load bearing walls, floors and roofs.

Many of our partners are working on exciting developments, using proven, reliable and viable panelised timber based offsite systems, which will soon transform how the housebuilding sector operates. As part of AIMCH, Barratt Developments PLC has created a Z House – a zero carbon concept house that applied 50 different solutions to understand how we will deliver the ‘sustainable home of the future’. It is located on the University of Salford’s campus with their scientists tasked with measuring its energy efficiency to provide hard data on the home's design versus actual performance.

The home’s clever design feature’s high performing energy efficient building fabric, using Barratt Developments’ internal timber framer Oregon’s advanced panelised timber systems at its core. The home incorporates PV solar panels and battery storage to generate and store power, electric car charging points and an air source heat pump that transfers heat from the outside to water for home heating and hot water use. Inside, underfloor heating, innovative infrared panels and skirting heating systems provide instant zero carbon heat, a fridge controls humidity levels to reduce food wastage by 60% and atomising showers that could cut water usage by 80%.

As research continues into sustainable housebuilding, developers and housebuilders can use AIMCH findings as a starter for assessing how they can lower embodied carbon emissions of materials used in construction and their impact on lower whole life carbon emissions. Such is the environmental benefits of building houses with timber components or build methods, the UK Climate Change Committee reports that the UK can triple the amount of carbon captured in homes by building 270,000 timber frame homes each year.

Where houses are built is changing too. Increasingly more homes today are manufactured offsite and assembled at the development. New offsite factories developed by AIMCH, are being designed to include PV electric power generation to run machinery, electric forklift fleets and EV car charging for employees, such that they produce more power than they use, with any surplus recycled back into the national grid, making the transition to net zero carbon manufacturing a supply chain reality.

In the long term, battery storage systems could be used in these factories to store power 24/7 for continuous manufacturing needs. In addition, zero factory waste goes to landfill and 100% of waste is either repurposed, reused or converted to energy through large-scale waste to energy plants.

The UK needs more homes. At the same time, we must play our part in limiting the dangerous impacts of the climate crisis and transition to net zero carbon homes and businesses.

Continuing with the status quo in the housing sector will likely see the UK fail on both fronts. However, I am confident that projects like AIMCH will catalyse industry to accelerate near to market, reliable, viable and sustainable offsite solutions that transform how homes are built. Additionally, this will increase housing output, while helping the UK meet its environmental obligations to limit climate change to 1.5C. 

PANELISED TIMBER A CARBON CUTTER

The report ‘Whole Life Carbon Assessment of Homes’ by AIMCH concludes that using sustainably sourced timber panelised offsite methods to build new homes rather than masonry products can reduce the carbon impact of construction.

On a whole life carbon basis, the study predicts that up to 5 tCO2 e per 4 bed dwelling, equivalent to 16,500 road miles, could be saved, when using timber panelised MMC methods.

Using the RICS Standard for Whole Life Carbon Assessment, the report represents a rigorous cradle-to-grave assessment of the carbon impact of both types of construction materials and their respective methodologies. 82% of emissions are generated from the homes operational use over 60 years, which is the same for both methods. 14% of emissions are generated from the materials and construction process. A small proportion of emissions are generated at end of life. 

The study, authored by green energy consultancy Verco, examined four types of home utilising either: masonry – aerated blockwork and offsite manufactured open and closed panel timber MMC, both with brick cladding. Carbon sequestration benefits of timber, in line with RICS protocols, were applied to all methods of construction, for example benefiting masonry homes bult with timber floors and roofs. End of life assumptions used identical 90% recycle/re-use and 10% to landfill ratio across both material types.

Cementitious products including roof tiles, concrete blocks, brick cladding, strip foundations and floor slabs, were found generally to have the highest lifecycle embodied emissions. Conversely, timber frame wall elements sent to landfill, were found to produce 0.5 tCO2 e emissions at end of life, compared to aerated concrete blocks.

Panelised timber construction methods outperformed masonry construction on a whole life carbon basis, when comparing the direct substitution of various wall elements – external, load bearing and party wall elements. Embodied emissions of these wall elements being as much as 82% less than that of the masonry construction. In addition, timber offsite key properties contributed to reduced emissions.

For more information and a detailed summary of AIMCH’s report Whole Life Carbon Assessment of Homes visit: www.aimch.co.uk

Read the full article, go to Offsite Magazine

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