Active Building Toolkit: Carbon
In 2019, the UK Government amended the Climate Change Act (2008) to set a target to reduce carbon emissions by at least 100% below 1990 levels by 2050.
Decarbonising the built environment sector is key to reducing energy use and greenhouse gas emissions. Globally, buildings account for approximately 40% of energy consumption and 28% of carbon emissions and hence are large contributors to global warming.
The UK Green Building Council (UK GBC) define the embodied carbon of a building as a consequence of the total carbon emitted during the creation of the individual elements of the building, added to the carbon emitted during the construction process.
The carbon emitted during the operation of a building depends on the efficiency of the building and the ease of maintaining the building using low carbon technologies. Operational carbon is also dependent on the life of the building, the ease of dismantling and the ability to re-purpose building elements, spreading the embodied carbon over as long a period as possible. (Source: National Federation of Builders)
Both embodied and operational carbon must be reduced if the UK is to meet its decarbonisation targets and should be fundamental to all design decisions.
- Key Design Considerations
- Carbon Offsetting
- LCA Methods
- Low Carbon Construction Materials
- Operational Carbon
Key Design Considerations
Low carbon site considerations for an Active Building:
- Site location
- Access to existing cycle routes and footpaths
- Access to public transport
- Landscaping within the site curtilage:
- Promote biodiversity
- Reduce runoff – minimise hard surfaces, maximise green spaces and other permeable surfaces
- Provision of outdoor exercise facilities
- Provision of cycle shelters
- Provision of EV charge points for a variety of EVs (see Principle 5)
- Adopt a life cycle assessment (LCA) methodology early in the project and use available databases in selecting materials and technologies (see page 35)
- All members of the Project Delivery Team should understand, record and publish their carbon footprint and then work to reduce it. This will be needed for calculating the carbon contribution to a project of all stakeholders.
- Work with your client and contractors to develop designs, specify products and use processes that can help reduce the embodied carbon of a project.Educate all stakeholders regarding the challenges, urgency and solutions to reduce carbon dependency on the carbon emissions from the construction industry.
- Use performance targets to drive down embodied and operational carbon of a building by all stakeholders involved in the building project.
- Consider use of Government Soft Landings to ensure that the operational carbon matches the original design parameters.
In their Embodied Carbon Primer, LETI describe offsetting as the use of carbon negative activities to remove greenhouse gases from the air and store them for long periods of time.
Net Zero Embodied Carbon is difficult to achieve currently (2020). While it should not be relied on to reduce carbon emissions from building projects, carbon offsetting can be used to help achieve Net Zero; and most carbon offsetting measures are beneficial, even if Net Zero can be achieved through embodied and operational savings. Some possible carbon offsetting measures include:
- Tree planting on-site or within the community
- Reducing energy demands of existing buildings by adding insulation and more efficient heating and cooling systems
- Including additional renewable energy generation
- Using a clean local energy supplier
- Investing in renewable energy schemes
- Supporting local community schemes
It is, however, difficult to accurately measure the benefits of carbon offsetting and it is not recommended to use this as a replacement for true Net Zero measures.
Further information can be found in Appendix 10 (p.109) of LETI’s Embodied Carbon Primer.
Assessing Whole Life Carbon (WLC) of buildings is necessary to mitigate against global warming caused by ‘human generated’ greenhouse gas (GHG) emissions to the atmosphere, commonly referred to as carbon emissions. Here are just some of the available assessment methodologies:
BS EN 15978:2011 – Sustainability of construction works. Assessment of environmental performance of buildings. Calculation method.
Sets out the calculation method to assess the environmental performance of a building, based on LCA for both new and existing buildings, providing a description of the object of assessment, system boundaries applicable at the building level, procedures used for inventory analysis, a list of indicators and procedures for calculation, reporting and data requirements. There are four main stages to carrying out an LCA:
- Goal and scope definition
- Inventory Analysis
- Impact Assessment
- Interpretation and Improvement
The bulk of the data collection takes place during the inventory analysis of an LCA, where inputs and outputs to the product are determined – inputs include the materials and energy required to make a product; and outputs are the waste and quantities of emissions caused by the production process.
Mandates a whole life approach to reducing carbon emissions within the built environment. It sets out specific mandatory principles and supporting guidance for the interpretation and implementation of the BS EN 15978 methodology.
A freely available framework for LCA to enable the development of flexible models using Open Source software.
IMPACT for LCA is a specification and database for software developers to incorporate into their tools to enable consistent LCA and Life Cycle Costing (LCC). IMPACT compliant tools work by allowing the user to attribute environmental and cost information to drawn or scheduled items in the Building Information Model (BIM), taking quantity information from the BIM and multiplying this by environmental impact and/or cost ‘rates’ to produce an overall impact and cost for the whole (or a selected part) of the design. The results generated by IMPACT allow the user to:
- analyse the design to optimise cost and environmental impacts.
- compare whole-building results to a suitable benchmark to assess performance, which can be linked to building assessment schemes.
The overall aim of IMPACT is to integrate LCA, LCC and BIM.
A fast LCA and LCC web-based tool, compliant with IMPACT, with access to a large LCA database. The tool is also compliant with BREEAM and many other green assessment methods.
The ICE database is the world’s leading source of embodied energy and carbon data and is free to download.
HB:ERT is a Revit-based tool that enables design teams to quickly analyse and clearly visualise the embodied carbon emissions of different building components and construction material options at any time during the design process. This is also free to download.
Low Carbon Construction Materials
Steel Screw Piles
Steel screw piles are a versatile, environmentally friendly and cost-effective foundation technology, ideally suited to lightweight structures; and are faster to install than most other foundation solutions. They are typically manufactured from high-strength steel using varying sizes of tubular hollow sections for the pile or anchors shaft.
For an example of screw piles in action, check out our Active Classroom Case Study.
Benefits of Screw Piles
- Quick to install – saving time, money and carbon
- No concrete or curing time – enables faster commissioning of sites
- Flexible design – frames can be designed to bridge services and other obstructions, allowing areas with congested services, for example, to be built on
- Installation in low temperatures is possible – no down time, unlike concrete
- Cost effective solution in soft ground, where traditional piling is more expensive and concrete is technically unsuitable
- Sustainable – they are removable and reusable
- Minimal vibration – working next to existing buildings is no issue
- No excavations or spoil to cart away – saving money (particularly if there is contaminated ground), transport, carbon
- Minimal noise – dependant on excavation, but most installs below 80db
Low Carbon Concrete Products
Concrete is the most widely used man-made material on earth; and cement, one of the key ingredients of concrete, is the source of about 8% of the world’s carbon dioxide (CO2) emissions. In fact, it has been reported that, if the cement industry were a country, it would be the third largest emitter in the world – behind China and the US.
There are two ways to significantly reduce the embodied carbon of concrete – one is to use a cement substitute and another is to reduce the carbon emitted of the manufacture of concrete.
Here are some examples of available low-carbon concrete products:
- Hanson EcoPlus® Range – sustainable concrete solution that replaces up to 70% of Portland Cement with Hanson Regen GGBS (Ground Granulated Blast Furnace Slag) – For more information you can book a free CPD seminar here.
- The process of manufacturing concrete is highly energy intensive and the second largest contributor to carbon in concrete products. An innovative project in Port Talbot, South Wales, is trialling generation of green hydrogen (via a wind turbine) to use as an alternative fuel source in the manufacture of concrete that utilises GGBS.
- Cemfree Concrete – an Alkali-Activated Cementitious Material (AACM) using GGBS and Pulverised Fly Ash (PFA) to create a binder to replace cement.
- Carbicrete – a Canadian company who combine cement substitutes, such as GGBS with carbon capture technology, where the carbon emissions from their industrial process are captured, hence reducing the amount of emissions being pumped into the atmosphere. Their future plans include use of direct air capture (DAC) to draw CO2 from the atmosphere.
- Cenin Renewables – at their site in Stormy Down, South Wales, Cenin utilise anaerobic digestion, wind and solar energy generation to manufacture ultra-low-carbon cement substitutes using recycled materials.
Reducing Thermal Bridging
- Schöck Isokorb® has been designed to thermally separate elements, such as balconies, parapets or canopy roofs, acting as part of the thermal insulation, while at the same time forming part of the structure. As such, the Isokorb ® products can significantly minimise thermal bridging issues.
- Keystone Hi-therm+ Lintels are thermally broken steel insulated lintels with a Psi value of 0.3 – 0.6 W/m2K, significantly lower than a standard insulated lintel.
Low Carbon Insulation
Many of the mainstream insulation products contain recycled content and/or are recyclable at end of life. ROCKWOOL, for example, use waste material from refurbishment and demolition, as well as off-cuts in their insulation products, which are themselves recyclable. They have a dedicated recycling facility in Bridgend, South Wales, where contractors can recycle unused ROCKWOOL insulation. Here are a few examples of other low carbon insulation products:
- Warmcel insulation is manufactured from recycled newspapers, with the addition of naturally occurring mineral salts, which provide fire resistance and fungal/insect protection.
- Thermafleece is a natural and sustainable sheep’s wool insulation made in the UK (using wool from UK sheep), comprising a blend of 75% wool with recycled polyester fibres, to provide the enhanced performance of sheep’s wool with durability and sustainability. It can be used in roofs, walls, lofts and floors and can be supplied in different sizes, formats and densities to suit different performance needs.
- Natural Insulations – manufacturers of Thermafleece – also manufacture other low carbon insulation products, including:
- SupaSoft – recycled plastic bottles
- Thermofloc – recycled newspaper
- NatraHemp – hemp fibres and recycled polyester
- Steico – wood fibre from forest thinnings
- Inno-Therm®/Métisse® consists of 85% recycled denim/cotton and is recyclable at end of life. It’s manufacture uses 70% less energy than conventional insulation, adding to its low embodied carbon credentials.
A London-based company, Biohm, have created a range of bio-based materials, for example mycelium to create building insulation that is naturally fire retardant and removes carbon from the atmosphere as it grows. Mycelium is a biomaterial that forms the root system of fungi, feeds on agricultural waste and in the process sequesters the carbon that was stored in this biomass. It is fast-growing and cheap to produce in custom-made bioreactors.
The lowest carbon cladding systems are those made of natural materials, such as timber. Recyclability of cladding is also an important factor – steel, for example is infinitely recyclable – and the lifetime environmental impacts of any cladding material can be checked via its Environmental Product Declaration (EPD). Cladding materials made out of recycled materials are also increasingly available. One example is recycled plastic cladding by a UK company called Kedel.
A German company called Made of Air has developed a carbon-negative bioplastic, using wood waste, that can be used for external cladding. The material contains biochar, a carbon-rich substance made by burning biomass without oxygen, which prevents the carbon from escaping as CO2.
External Doors and Windows
Glazed elements of a building envelope are often the biggest sources of heat loss, but this can be mitigated through use of high performance glass units and through framing choices. Timber frames, for example, have better insulating properties than metal or uPVC frames. However, timber requires more maintenance than the man-made alternatives. Combining materials such as timber and aluminium can provide a solution to this, and there many manufacturers who provide this hybrid solution. A couple of examples are:
- Norrsken: a UK manufacturer of high performance, double or triple glazed, timber framed windows and doors, with exterior aluminium cladding.
- Vellacine: another UK organisation manufacturing aluminium clad timber framed windows.
This combination is beneficial to overall building performance, as the timber frames have a low thermal conductivity, while the exterior aluminium cladding provides a durable and low-maintenance outer skin.
These manufacturers also deploy other measures to further reduce their carbon footprints. For example, to minimise waste, the sawdust from Norrsken’s manufacturing process is used for heating; while Vellacine collect recycled glass from old windows for reprocessing into new glass units.
Internal Finishes for good Indoor Air Quality
- Auro Breathable Paints: A wide range of natural plant and mineral based, paints, free from synthetics, pollutants and non-degradable plastics. The use of natural materials creates healthy indoor environments.
- Dulux Forest Breath Eco-sense: A high-tech emulsion paint with an air purifying function designed to capture formaldehyde and a range of other VOCs (Volatile Organic Compounds), as well as effectively killing bacteria. The paint utilises solvent-free technology which incorporates natural bamboo and charcoal to give it anti-bacteria, anti-virus anti-benzene and anti-formaldehyde properties.
The National Grid Electricity System Operator (ESO) has developed a Carbon Intensity (CI) forecast of the electricity grid in Great Britain, with a regional breakdown. This can be utilised to determine the CI of all the electricity consumed by a building at any time of the day. To use the Active Office as an example, the graph below indicates the difference between the CI of electricity used from the battery to that of the CI of the grid. The grid CI of South Wales is higher than most other regions in Great Britain, due to the location of Tata Steelworks in Port Talbot. The graph below clearly demonstrates the impact use of renewable energy sources and energy storage can have on the operational carbon of a building.
- RIBA. 2019. Embodied and whole life carbon assessment for architects.
- RICS. 2018. Whole Life Carbon Assessment for the Built Environment.
- World Green Building Council. 2019. Bringing embodied carbon upfront.
- BSI. 2020. PAS 2080: Carbon Management in Infrastructure Verification.
- Wrap. Designing out waste: a design team guide for buildings.
- BRE. 2020. Background to the Green Guide to Specification.
- Circular Ecology. Net Zero Carbon Construction.
- Cabinet Office. 2013. Government Soft Landings.
- LETI. 2020. Embodied Carbon Primer.