Beyond efficiency in net zero housing: how councils can reduce embodied carbon

This is the featured story in this week’s Global Local Recap on low carbon housing. 

Over the next 30 years, putting in place the conditions to drastically decarbonise – or even reach net zero, as 61% of countries have pledged – will be a formidable task for governments globally. Representing 38% of worldwide emissions, the buildings industry must be a priority for change, and is an area in which local government’s impact could be instrumental.

Carbon emissions from buildings fall into two categories: operational carbon, which describes the energy used in running a building; and embodied carbon, created primarily through construction and demolition (including raw materials extraction, manufacture and transport etc.). Great progress has been made in recent years to improve the energy efficiency of homes for both retrofit and new-build, with guides and certifications – such as the gold standard of Passivhaus – filtering into building regulations, and the use of heating pumps and renewable energy becoming more commonplace (though perhaps not fast enough for many countries). Certainly, the twin benefits of reduced emissions and reduced household bills has played a part in the boom of help and resources, and housebuyers increasingly want eco-homes and know what to look for.

However, while improving operational carbon emissions has traditionally received the most attention in climate housing initiatives – and does currently constitute the largest chunk of emissions – a large proportion of the carbon emitted during a building’s lifecyle will be embodied. In fact, as housing energy efficiency continually improves and as energy production moves to renewable, operational carbon will no longer be responsible for the majority of emissions in a building’s lifecycle.

With this in mind, adopting a ‘retro-first’ approach to reusing and repurposing buildings instead of replacing them should be high on the agenda, as outlined in this LGIU briefing. Where such an approach won’t work, or when new housing developments are required – as they will be to solve the global housing shortage – we should look to improve both embodied and operational carbon emissions. With the urgency of climate change, a kg of CO2 saved now in construction is more valuable than the same amount saved over the next 30 years in running costs.

Embodied carbon

Regulations for embodied carbon tend to be less developed compared to regulations for energy efficiency – in many countries, there is still no regulation at all. While it is gaining momentum, the concept is still fairly new, and so there are many untapped opportunities to address embodied carbon in buildings that represent low hanging fruit – choosing to consider them during construction does not have to result in dramatically increased costs. There are valid arguments to considering embodied carbon from a cost standpoint, as much of the premise revolves around efficiency; evident from some of the core ideas outlined below:

• The identification of designs that optimise pre-existing building or structure use, especially preserving foundations where most of the embodied carbon resides.
• Utilising a more efficient use of resources and materials, e.g: using high-recycled content materials; salvaged materials; designing using modular methods or common sizes such as 4×8 plywood; maximising structural efficiency – such as optimum value engineering framing or lightweight floor construction.
• Using more resilient materials or ones that are more appropriate for the expected lifetime of the building/element.
• Reducing the use of carbon-intensive materials (e.g. virgin steel, aluminium, plastic or foam insulation) while opting for low carbon materials or even carbon-sequestering ones where possible (e.g. wood, low-carbon concrete mixes, hemp insulation, bamboo).
• Improving transportation and construction efficiency to reduce not only embodied carbon, but also cost. This may include modern methods of construction such as modular pieces mass-manufactured offsite which reduce wastage and transportation emissions.

Rating systems such as BREEAM, LEED and Green Star all take into account embodied carbon measurement and mitigation as part of minimising building life cycle impacts. The World Green Building Council’s report Bringing Embodied Carbon Upfront provides a helpful, multisectoral exploration into the challenges and solutions accounting for embodied carbon can bring to construction. The Carbon Neutral Cities Alliance has produced a City Policy Framework for Dramatically Reducing Embodied Carbon, containing 52 detailed policies for municipalities to consider, stretching beyond housing and into public realm developments.

So how can local authorities lead on low carbon housing?

The role of local authorities could be direct, leading by example – working to build houses or public buildings to low-carbon specifications. In Leeds, England, the pioneering Climate Innovation District will soon reach 1,000 homes (and an office, school and care home) – having been fabricated just across the road to use timber panels and wood-fibre insulation and take just a week to erect. Using low operational carbon methods and solar panels for energy, the houses will use 10x less energy than the average house and in fact create excess electricity to feed into the community grid. In Exeter, the council has been building low carbon social housing for over 12 years to Passivhaus standards to combat fuel poverty while aiming ambitiously for net zero by 2030.

Alternatively, councils can target the industry through standards. In many countries, including the UK, local authorities have powers to set higher emissions standards for developments than national building regulations apply. The City of Vancouver, Canada, has created a regulatory framework mandating that embodied carbon be considered in new buildings and reduced by 40% by 2030. Considering where to allow buildings to be built is also important – locations where low carbon transport options can be used as opposed to isolated areas with poor services, forcing all residents to use cars. The City of Helsinki, Finland, has applied wood requirements in several district zoning projects, in some cases requesting a wooden frame and façade. The Carbon Neutral Helsinki 2035 program requires zoning officials to incorporate carbon-reducing practices. Taking a different approach, the Austrian state of Vorarlberg provides grants for low operating or embodied carbon in new houses.

Lastly, councils can be instrumental in overcoming some of the largest barriers to low carbon housing method adoption – inertia from construction firms and skills shortage in the relevant techniques for building, often due to use of unconventional materials or techniques. Whether it be through standards or engaging in discussions or agreement with local developers and stakeholders, creating pressure to consider the carbon footprint of buildings for their whole lifecycle is important. Equally, the construction industry currently faces severe skills shortages in eco-construction and retrofit methods, with low demand contributing to under-investment in skills and capacity building. Without a trained workforce, there is limited scope for choice in construction methods – and the scarcity may also push up costs. Research from the Construction Industry Training Board (CITB) in Scotland estimates that an additional 22,500 net-zero trained construction workers will be needed by 2028. Councils may be able to lead change locally, not only by ensuring demand for low-carbon construction soars, but also by looking out for opportunities to improve training, such as by mapping the skills and training offered at local education institutions with the opportunities afforded by local housing strategies.

Referring back to Exeter City Council, the success of the passivhaus developments has been built on with the setting up of the Exeter Sustainable Energy Efficient Developments (EXESeed) Contractors Framework. This four-year agreement proves a commitment to collaborate with developers to tackle energy inefficiency in housing and fuel poverty. The framework will be used by the City Council to procure local and national contractors for the Council’s pipeline of energy-efficient developments. The Framework will also encourage contractors to create local apprenticeship opportunities creating additional benefits for the local economy. Exeter City Council would like to encourage other public sector bodies such as local authorities, universities and the NHS to use the Framework to provide access to building contractors committed to delivering low energy sustainable developments. Going forward, Exeter City Council plan to build a Passivhaus Academy in the City which aims to:

“provide a focal point for the essential skills needed to deliver new buildings, and the requirements for retro-fit, providing a workforce that is skilled, knowledgeable and professional. Training and skills development will be delivered in a purpose built centre in the city, and also through an online platform, to support reach beyond the city and region, sharing our skills and experience to as wide an audience as possible.”

Complex global issues require action at the local level more than ever. Sign up here to receive the new, free Global Local Recap by LGIU. This week’s edition puts a spotlight on low carbon housing.