Mesh Energy                            SBE0040

Written evidence from Mesh Energy


How materials can be employed to reduce the carbon impact of new buildings, including efficient heating and cooling, and which materials are most effective at reducing embodied carbon.


Mesh Energy is an independent energy consultancy helping architects, homeowners, and commercial clients to create low-energy buildings from first principles and integrate appropriate sustainable energy solutions. Mesh Energy was founded by low-energy expert Doug Johnson.

Working across sectors, on new build houses, existing homes, developments, and commercial property Mesh’s expert team offer the following services:


              SAP, EPC, SBEM assessments

              Building fabric advice and optimisation

              Dynamic thermal modelling and overheating analysis

              Ventilation modelling

              Embodied carbon analysis

              RIBA 2030 analysis and benchmarking

              Renewable energy strategy and feasibility studies

              Renewable energy tender specification and design

              Full mechanical and electrical design

              Sustainable product installer recommendations


1.1              Executive Summary


The evidence submitted arises from a project currently at RIBA Stage 4 ‘Technical Design’. The project design team environment is highly collaborative and transparent in seeking an outstanding outcome in sustainable building performance and design. This statement will focus on the embodied carbon and whole life carbon of the project.


The project is creating an entirely new approach to working with justice involved women. In a healing, residential environment, women will be supported through a positive, compassionate and trauma informed approach to achieve better outcomes for women, their children and society. Due to the centres unique aspirational and ground-breaking nature, it has been crucial that anyone working on the project is faithful to its concept.

Figure 1 Project design

      The embodied carbon and whole-life carbon was assessed for this Building Research Establishment Environmental Assessment Method (BREEAM) Outstanding project using Building Research Establishment (BRE) Integrated Material Profile And Costing Tool (IMPACT). This tool is compliant with Building Information Modelling (BIM) software. The purpose of the analysis was to enable One Small Thing and the wider project Design Team to understand the impact of the choice of principles of construction and building services strategy throughout the building lifecycle.


      Three significantly different superstructure, substructure and hard-landscaping design options were modelled using the BREEAM methodology. Variations in vertical structures and façade, horizontal structures (beams, floor and roofs), other structures and materials (stairs, doors, glazing) and building technology were also compared.


      The embodied carbon of a cross laminated timber building is reduced by 49% in comparison with a steel frame and concrete deck building, while the whole life carbon of a cross laminated timber building is 51% less than a steel frame and concrete deck building.


      The client requirement for a robust collaborative design approach in designing a sustainable high-performance building that exceeded the requirements of the local Core Strategy has resulted in;

      A 63% reduction in embodied carbon.

      An 86% reduction in operational carbon emissions.

      A 51% reduction in whole-life carbon.


      The analysis demonstrates at RIBA Stage 3 that the RIBA Stage 2 Concept Design criteria can be met. This approach will meet the RIBA Sustainable Outcome for embodied carbon for 2030 and seek to deliver a BREEAM Outstanding building.


1.2              Introduction


One Small Thing set out to create places where women can imagine themselves differently and get the support and tools to achieve this reality for themselves and their children. People walking through the door may not have ever experienced their needs being met or feel a sense of worth in their lives – our aspiration is that they will leave Hope Street feeling stronger and empowered.

One Small Thing aspire for their buildings to be examples of sustainable design, in all considerations from the ventilation of spaces to the light, material selection and service systems. They should be as considerate to the environment as they will be to the people using them.

1.3              BREEAM


The BREEAM methodology embedded sustainability at RIBA Stage 0 in defining the brief at Stage 1 that led to a conceptual sustainability strategy that is being technically realised, to then be delivered and maintained. This facilitated design team approach that progressed from aspirational and contextual thinking to applied holistic design and detailed definition through collaboration between stakeholders and design practitioners in exceeding the requirements of the local Core Strategy.




1.4              RIBA 2030 Sustainable Outcomes


RIBA has developed the 2030 Climate Challenge to help architects meet net zero (or better) whole life carbon for new and retrofitted buildings by 2030. It sets a series of targets for practices to adopt to reduce operational energy, embodied carbon and potable water that will support the 17 UN Sustainable Development Goals.


Today the non-domestic embodied CO2 benchmark is 1100 kgCO2e/m2. The RIBA 2030 embodied CO2 targets are:

        By 2020 a reduction in embodied CO2 to <800 kgCO2e/m2

        By 2025 a reduction in embodied CO2 to <650 kgCO2e/m2

        By 2030 a reduction in embodied CO2 to <500 kgCO2e/m2


The RIBA Sustainable Outcomes approach acts as a pathway for step changes. if we follow the trend through to 2050 there is good cause to be optimistic that achieving net-zero energy will be routine by 2035 and that embodied carbon will be sequestered within the lifetime of a building.

Figure 2 Net-Zero carbon pathway

1.5              Life-cycle analysis


Lifecycle Analysis (LCA) is a method for evaluating the environmental load of building’s during their lifecycle from cradle to grave. LCA includes the energy and materials used, along with waste and pollutants produced as a consequence of a product or activity are quantified over the whole lifecycle.

1.6              Embodied carbon


Embodied CO2 is a measure of the energy used in the extraction, fabrication and transportation from place of origin of the materials used in the construction for the lifecycle of the building. Biogenic carbon is the carbon that is sequestered in biological materials, such as plants or soil. Carbon accumulates in plants through the process of photosynthesis and therefore bio-based products can contribute to reduce the levels of carbon dioxide in the atmosphere and help mitigate the challenge of climate change. Biogenic carbon within a building product can therefore be considered as a "negative emission". This means that during the growth stage of bio-based materials carbon is stored into the material.


1.7              Software compliance


A Level-5 dynamic thermal model has been constructed in Integrated Environmental Solutions Virtual Environment (IES-VE) using the Chartered Institute of Builing Services (CIBSE) weather files in accordance with CIBSE AM11 ‘Building performance modelling’.

The BIM materials and energy consumption data has been exported into One Click LCA for the purpose of completing a whole building life-cycle assessment.


        The tool is compliant with BREEAM UK New Construction 2018 technical guidance.

        The life-cycle costing is carried out in compliance with ISO 15686-5 standard.

        The tool is also third-party verified for EN 15978, ISO 21931-1, ISO 21929-1 and for input data for ISO 14040/44 and EN 15804 standards.

The  LCA analysis consists 10 design variations to explore variations in the building at RIBA Stage 3 while retaining the same functional requirements for each variation:


        Foundations and substructure.

        Vertical structures and façade.

        Horizontal structures - beams, floor and roofs.

        Other structures and materials – stairs and glazing.

        External areas.

        Building technology.

The analysis included:

        Comparison with the BREEAM LCA benchmark during RIBA Stage 2 Concept Design.

        Option appraisal during Concept Design.

        Substructure and hard landscaping options appraisal during Concept Design.

        Core building services options appraisal during Concept Design.

        LCA and LCC alignment.

1.8              Design Variation Analysis


The study provided a range of outcomes in terms of carbon and cost, with the least and most impactful as shown in Table 1.



Least embodied carbon

Most embodied carbon


Embodied carbon

Cross laminated timber with air-source heat pump or biomass

Steel frame and concrete deck with gas and electricity

361 kg CO2e/m2

Whole life carbon

Cross laminated timber with biomass

Steel frame and concrete deck with gas and electricity

1,179,683 kg CO2e

Life-cycle cost

Cross laminated timber with gas and electricity

Steel frame and concrete deck with air-source heat pump


Table 1 Study outcome summary

The embodied carbon of a cross laminated timber building is reduced by 49% in comparison with a steel frame and concrete deck building, while the whole life carbon of a cross laminated timber building is 52% less than a steel frame and concrete deck building. This approach will meet the RIBA Sustainable Outcome for embodied carbon for 2030.


1.9              Fabric Performance


The fabric first approach requires significantly improved U-values with low and zero thermal bridging details at key none repeating junctions. High levels of air tightness will be achieved through the use of air tightness membranes connecting the building elements and around building penetrations as shown in Table 2.


Building Element

Building Regulations (W/m2K)

Business as usual




Overall improvement

External wall





Ground floor










Air tightness

10 m3/h.m2@50Pa

5 m3/h.m2@50Pa

3 m3/h.m2@50Pa


Part L BER

23.5 kgCO2/m2


3.2 kgCO2/m2


Table 2 Relative performance of building fabric

1.10         Embodied Carbon Outcome


Using Royal Institution of Chartered Surveyors (RICS) data, each design variation for a building element was found to have the embodied carbon as shown in Table 3. Timber frame construction was discounted for analysis of building services variations as timber frame construction was found to have similar embodied carbon to cross laminated construction. Cross laminated construction was favoured for architectonic reasons. Variations in construction and energy strategy were then compared to understand the embodied and whole-life carbon, as well as lifecycle cost. The design variations are illustrated in detail in Appendix A.


Building Element

Design variation

Embodied Carbon (kg CO2e)

Super structure above ground

CLT (net carbon)


CLT (sequestered carbon at end-of life)






Substructure below ground

Concrete footings


Steel core piling


Rammed concrete piling


Hard landscaping

Quarried stone




Resin-bound decorative aggregate


Building services strategy



Gas, radiators MVHR, Solar PV


Biomass, UFH, MVHR, Solar PV


CLT (cross-laminated timber), ASHP (air-source heat pump), UFH (underfloor heating), MVHR (mechanical ventilation and heat recovery)

Table 3 Building element embodied carbon

In completing and overheating assessment in accordance with CIBSE TM52 ‘The limits of thermal comfort: avoiding overheating in European buildings’, the design was found to be naturally cooled. The mitigation of the need for air conditioning reduces embodied, operational and whole life carbon.

1.11         Whole Life Carbon and Cost Outcome


The life-cycle costs are calculated for a fixed 60-year assessment period using RICS data on a per Gross Internal Floor Area m2 basis for all:


        Building materials, and do consider the given quantities of material, materials transports, and material replacements required during the building assessment period as well as the end-of-life processing.

        Annual energy consumption.

        Annual water consumption.

        Other capital costs.

        Other operating costs.


In order to be able to add and compare cash flows that are incurred at different times during the life cycle of a project, they have to be made time equivalent. To make cash flows time-equivalent, the LCC method converts them to present values by discounting them to a common point in time, usually the base date. For the purpose of this report the discount factor (capital cost and inflation rates) are:


        Discount rate (cost of capital) 7%

        General inflation rate 2%

        Energy inflation rate 2%

        Water inflation rate 2%

        End of life as a percentage of CAPEX 2.5%


The study provided a range of outcomes in terms of carbon and cost, with the least and most impactful as shown in Table 4.


Design variation

Embodied Carbon         (kg CO2e/m2)

Whole Life Carbon         (kg CO2e)

Lifecycle cost

Cross Laminated Timber ASHP




Steel Frame ASHP




Concrete Frame ASHP




Timber Frame ASHP




Cross Laminated Timber Gas and Electricity




Steel Frame Gas and Electricity




Concrete Frame Gas and Electricity




Cross Laminated Timber Biomass




Steel Frame Biomass




Concrete Frame Biomass




Table 4 Design strategy whole life carbon and cost

1.12         Conclusion


This project demonstrates that there are already many existing design tools, methodologies and standards that encourage sustainable building performance and design. The most well known in the UK is BREEAM, and more recently the Well Building Standard (WELL). Both allow a robust and transparent collaborative approach and place low-carbon buildings with occupant health and wellness at the heart of the design and use of buildings throughout their lifecycle.

The client requirement for a robust collaborative design approach in designing a sustainable high-performance building that exceed the requirements of the local Core Strategy has resulted in;

        A 63% reduction in embodied carbon.

        An 86% reduction in operational carbon emissions.

        A 51% reduction in whole-life carbon.

The UK planning system has the most significant role to play in delivering a sustainable built environment, for example the National Planning Policy Framework (NPPF) should be used to set robust requirements for sustainable building design and performance, setting a National Core Strategy. The NPPF provides a mechanism for presumption in favour of sustainable development through the re-use and refurbishment, exceeding the requirements of the local Core Strategies.

A National Core Strategy that sets milestones to achieve net-zero by 2050 entered into law, and aligned with UN Sustainable Development Goals, would facilitate the required improvements in sustainable building design and performance for the five time periods. This clearly defined pathway would enable the necessary holistic step-change in architectural vernacular for a changing climate, labour skills, technology, materials, green and blue infrastructure, energy use and water consumption behaviour.

By setting national planning and Building Regulations milestones for 2022, 2029, 2036, 2043 and 2050 today, with all new projects conforming to that year in which they are to be constructed regardless of the year in which they are designed, would provide a robust pathway to net-zero. Such a framework would need additional support through Approved Documents and taxation setting out limits for embodied carbon as this would favour the re-use and adaptation of existing buildings.

IMPACT-compliant software that uses RICS data, such as OneClick LCA, enables embodied carbon and whole life carbon to be calculated against independently certified manufacturer Environmental Product Declaration’s (EPD). This encourages low-carbon products to be brought to market and favoured in the realisation of projects in the built environment.

As the afore mentioned project sets out to prove, embodied, operational and whole life carbon can be significantly reduced today through robust legislation and design practices that encourages sustainable building performance and design.

May 2021

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