Summary of LETI Climate Emergency Design Guide — How can new buildings meet the UK`s climate change targets?
By Manon Dangelser
What is LETI?
The London Energy Transformation Initiative (LETI) was established in 2017 to support the transition of London’s built environment to net zero carbon; they provide guidance that can be applied to the rest of the UK.
Why a Climate Emergency Design Guide?
The UK Parliament declared a Climate Emergency in May 2019, following the publication of the Special Report on Global Warming of 1.5deg by the IPCC in October 2018. In this context, and because almost 50% of annual carbon emissions are attributable to buildings in the UK, it was urgent to create a guide that would help developers, designers, policymakers to reduce carbon emissions significantly.
More than 100 industry experts contributed to creating the Climate Emergency Design Guide, and highlighted five main elements to address the global warming effect and ensure climate change targets are met:
1. Operational Energy (energy use in buildings based on demand, what is designed and what is available from the grid)
2. Embodied Carbon (materials, transport, construction, maintenance & disposal)
3. Future of Heat (move away from fossil fuels & reduce heating demand)
4. Demand Response (minimise demand on the grid)
5. Data disclosure (measure, record and share energy data throughout the life of the building — 5-year post-completion check)
The full guide is available here: https://www.leti.london/cedg. And you can also find on the same page the four building archetypes that will make up the majority of new buildings in the UK (about 75%) between now and 2050: small scale residential, medium and large scale residential, commercial office and school.
What does Net Zero Carbon mean?
Net zero carbon for buildings means that the whole life carbon cycle of the building must be considered, i.e. must comprise embodied carbon and operational carbon.
As described in the guide, a building that is whole life net zero carbon meets the operational zero carbon balance and is 100% circular, this means that 100% of its materials and the building is designed for disassembly i.e. all materials and products can be reused in future buildings.
It is to be noted that LETI does not include carbon offsets to achieve the net zero operational carbon balance. Instead, a focus on circular economy and a detailed LCA will lead to this goal, in addition to Energy Use Intensity (EUI) targets. The EUI represents the annual measure of the total energy consumed in a building, and the design guide sets targets so that each new building does not exceed its ‘energy budget’. Therefore all developments can achieve operational net zero carbon at the scale of the UK (as the amount of renewables that the UK can produce is limited).
What is the Embodied Carbon Primer?
The Embodied Carbon Primer is a complement to the main guide that focuses on best practice for reducing embodied carbon. Operational carbon has still the biggest part in whole-life carbon; but this is about to change with energy efficient measures and heat pumps to be introduced more and more in design, as well as renewable. Therefore embodied carbon will become increasingly important in the following years and the main part to reduce to achieve net zero.
The Primer gives best practice targets for 2020 and 2030 for embodied carbon (chapter 7.0):
· 2020 target: 40% reduction over baseline with 50% of materials to be reusable and 30% to be reused;
· 2030 target: 65% reduction over baseline — and emphasising the importance of the circular economy.
The Primer also presents a RIBA description for each stage; for instance, for the first three stages:
· Stage 0 — Strategic Definition: Appendix 1: How to talk to your client > engage from the first stage the client and talk about whole life carbon. Assess what their ambitions are. Review the opportunity to retain the existing structure/fabric and how to reduce materials.
· Stage 1 — Preparation and Brief: talk about embodied carbon reduction targets. Appoint an LCA specialist or design team member responsible for the whole life cycle carbon assessment.
· Stage 2 — Concept Design: Use the rule of thumb guidance to maximise opportunities for low carbon design. Analyse carbon reduction options using numerical analysis.
Appendix 6 (Rules of thumb) is useful to learn how to reduce embodied carbon by building element and how to carry out reduction calculations: from a baseline model, you apply rules of thumb (described p.49–84 — including case studies — for each part of the building, how to use fewer materials, reduce waste etc.) and consider the “big ticket” items on which you can have an impact, for example, the superstructure. Then you identify your carbon reduction strategy and finally determine an optimised model and the measures needed to achieve the % reduction required.
LETI concluded that it is possible to reduce the embodied carbon of buildings by around 10–20% with simple cost-neutral measures.
