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MAT 01 - Environmental Impact of Materials

Information correct as of 27thJanuary 2022. Please see for the latest compliance information.

Assessing basement external walls - KBCN0241

Only the external walls above ground level are required to be assessed under this issue. The external walls below ground (i.e. within a basement area) perform a specialist function, these are not comparable with other walls in a building.These are therefore excluded from assessment under this issue.  

Astroturf (artificial grass) - KBCN0106

This is not be considered as hard landscaping and should be excluded from the assessment of this issue.  

Boundary Protection - KBCN0753

Only boundary protection specifically forming the site boundary should be included in the calculations. This may not necessarily be located on the boundary of ownership, but is the physical barrier which ostensibly encloses the development. Any other freestanding walls or fencing within the site can be excluded.

BRE Environmental Profile certificates - KBCN0777

BRE Environmental Profile certificates are compliant EPDs and can be used as evidence for the purposes of Mat 01.

Building LCA tools recognised by BREEAM - KBCN1118

The following table shows the building LCA tools that are recognised by BREEAM for each BREEAM scheme. Only submissions from the tools listed here will be accepted as part of a BREEAM assessment. These recognised tools may be either an IMPACT Compliant tool or another type of building LCA tool that has been evaluated by BREEAM and considered suitable for carrying out building LCA according to BREEAM’s scheme specific requirements. To apply for a new tool to be evaluated, please contact: Where more than one version of the same tool is listed for a given scheme version, the most recent version of the tool (that is available at the point building LCA work commences on the project) should be used. Click on the thumbnail for the full table.        
Table updated to include new recognised LCA tools 26/02/2020

Certificate validity - KBCN0798

EPDs and Green Guide ratings which have expired or are pending verification at the time the relevant product was specified, cannot contribute to awarding credits.  
04/11/2019 Confirmed applicability to UK NC2018
27/03/2020 Added applicability to Green Guide ratings and ISO 14001 certificates
27/05/2020 Reference to ISO 14001 removed - Whilst the same principle applies, the wording relating to product specification does not - See KBCN1401.

Cut-off threshold for responsible sourcing - KBCN1409

For projects pursuing the one separate credit under Responsible Sourcing of Materials (where at least three of the material types listed in the material categories have been responsibly sourced), any material type which clearly accounts for less than 1 m³ per 1000 m² of gross internal floor area, can be excluded from the assessment. This applies for materials in any location or use category. The volume considered should be taken as the construction product's overall external dimensions, including any internal voids and air spaces. Minor fixings (brackets, nails, screws etc.), adhesives, seals and ironmongery would normally fall below this threshold.

Definition – Reused in situ with minor repairs - KBCN1160

This item in Table "Allocation of points awarded" refers to the Relevant definitions section. This reference is incorrect and should, instead, point to the Compliance Note "Repairs to existing in situ elements", which indicates that, 'Materials used to repair existing in situ elements may be excluded provided no more than 20% of the total area; or volume of the existing element is subject to minor alternations, repair or maintenance'.
To be amended in the next re-issue of the technical manual.

Evidence requirements for Mat 01 Calculator - KBCN0675

The following evidence requirements, taken from the BREEAM International New Construction 2016 manual, give further information on the evidence that can be used to demonstrate compliance. This will be added to the next manual re-issue and will be required as evidence. Evidence requirements Note: Aside from the likely benefit to the environment from teams using LCA tools, the objective for BREEAM is to gather LCA performance data in order to create benchmarks and inform future updates of the scheme. The evidence requirements below are generic, but BRE Global understand that some tools are not able to fulfil all of the criteria. Where this is the case, the tool operator should submit results as close as possible to that required for the tool. IMPACT compliant tools A copy of the full IMPACT project or building file submitted by the assessor to BRE Global must be transmitted in the following format:
  1. For 3D CAD or building information model (BIM) based IMPACT compliant tools: In Industry Foundation Classes (IFC) or the IMPACT Compliant tool’s native format.
  2. For spreadsheet-based IMPACT compliant tools: IFC, MS Excel or comma-separated variables (CSV) file format.
  3. Building element categorisation to be according to New Rules of Measurement (NRM) Royal Institution of Chartered surveyors (RICS).
  4. A table in MS Excel or CSV file format listing each building element with, for each one, the information listed under 2 b, c and d (from the 'other tools' section), along with the NRM classification.
Other tools An electronic data table or tables of results (suitably cross referenced) generated by the tool, submitted by the assessor to BRE Global must fulfil the following criteria:

Submit a total building environmental impact result for year 0 (installation only) and year 60 study periods, as follows:

Results for each element as follows, to enable project team members and assessors without an IMPACT Compliant tool to check the accuracy of the model:

Transmitted in IFC, MS Excel or CSV file format.

Data permissions Submission of information to BRE Global for the purpose of assessing this issue will be required at QA stage. The submission is deemed to grant permission for the BRE Group of companies to use the information to:

Fulfil BREEAM quality assurance requirements

Conduct further research (using anonymised data), including for the establishment of robust building level life cycle performance benchmarks in BREEAM and BRE associated tools and methodologies.

Technical manuals to be updated accordingly in next reissue.

Exemptions from hard landscaping and boundary protection - KBCN00062

Where a third party, such as the local authority, enforces strict constraints on the materials that can be used by the project for hard landscaping or boundary protection, and these materials do not achieve a Green Guide rating of A/A+, it is possible to exempt these materials from the assessment of this issue, on the condition that robust evidence confirming this is given. In this instance the developer does not have control over the materials specified, therefore it is not appropriate to include them in the assessment.    

Gabion as boundary protection - KBCN000008

A gabion can be excluded from the assessment if it acts as a retaining wall or any other form of a supporting structure. If it acts purely as a boundary and a generic Green Guide rating cannot be found for a specification, the BREEAM assessor will need to submit a Bespoke Green Guide Query proforma detailing the specification details.  

GN08 – Scope of IMPACT compliant tools and data submission requirements - KBCN0621

Scope of IMPACT Compliant (or equivalent) Tools and Data Submission Requirements - BREEAM UK New Construction 2011 and 2014 Introduction This Guidance Note relates to complying with the exemplary level criteria for route 2, as defined under the Mat01 issue of the BREEAM New Construction 2011 and 2014 versions. It provides information about IMPACT and the level of detail (the Quality Requirements) and file transmission requirements for the Building Information Model (BIM) from IMPACT compliant (or equivalent) tools. It also outlines criteria for demonstrating the equivalence of a proposed alternative to IMPACT compliant tools for BRE Global approval. View full Guidance Note (licenced assessors only) View all Guidance Notes (licenced assessors only)

Green-roofs - KBCN0263

When assessing green roofs,  only the structural elements of the roof construction need to be considered i.e. the waterproof layer and above can be excluded. Where Green Guide is being used to assess the issue, it is likely that the online Green Guide Calculator will need to be used to provide a rating for the roof construction. HQM - For the purpose of HQM, green roofs fall under 3.3 Specialist roof systems therefore should be included in the IMPACT model.

IMPACT compliant software - KBCN0809

For a list of all IMPACT compliant software please see How to get IMPACT on the IMPACT website.

LCA modelling for multiple BREEAM assessments - KBCN0960

Multiple buildings' assessments Site-wide approaches are not acceptable and each BREEAM assessment needs to have its own Life Cycle Assessment model (using an IMPACT compliant software tool or equivalent). This applies in all cases, including when the buildings are on the same plot and are built to the same specifications. Developing assessment-specific LCA models ensures that material quantities are accurate, refer to the actual building (and building type) and account for external works included within the scope of the specific assessment. Single building with multiple assessments within it Where multiple assessments are conducted for different parts of a building, it is acceptable to have a single LCA model covering all assessments. In this case, an explanation of the allocation process used should be provided and the following guidance applies:

Life cycle environmental impact of curtain walling - KBCN0178

Curtain walling performs two functions – the provision of windows and the provision of external walls. Specifications performing the same function are grouped together in the Green Guide to Specification.  This means that curtain walling needs to be modelled as two separate building elements (external walls and windows). The overall performance of the curtain wall will combine the ratings for the two parts according to their areas. It will depend on the curtain walling system selected, the choice of internal lining and the relevant proportion of glazed and opaque elements.
  1. For the opaque area of the external wall (Area A in the figure below):
    1. Select the relevant generic specification from the Green Guide (element category – External walls / Curtain walling, then either aluminium or timber framed and the internal skin specification) and note the rating and element number. If your specification is different from all of the generics, please submit a request for a bespoke rating.
    2. Enter the rating into the BREEAM Materials calculator with the area for the opaque section of the curtain wall (Area A).
  2. For the glazed (window-like) area of the curtain wall (Area B):
    1. Select the relevant specification from the Commercial window element category of the Green Guide. There are two specifications: Aluminium curtain walling system (Element no: 831500016) and Laminated timber curtain walling system (Element no: 831500015)
    2. Enter the rating into the BREEAM Materials calculator with the area for the glazed (window-like) section of the curtain wall (Area B).
The BREEAM Materials calculator will calculate the overall performance for the curtain walling system. It will also calculate the performance of the building elements and the overall number of credits to be awarded.      

Mat 01 / Mat 03 calculator not big enough - KBCN0647

If a project has more specifications than there is rows available in the tool you can group specifications that have the same green guide rating/responsible sourcing level with each of the specifications with the same rating listed in the same row. The proportion that they contribute to the overall area is also combined. For example where a project has 30 different upper floor specifications, if 10 upper floor specifications are A+, 10 are A, 5 are B and 5 are C then you would only need to use 4 lines.

Mat 01 Calculator Option 1 – verified LCA tools - KBCN0237

Before an LCA tool can be recognised by BREEAM, the tool developer must submit evidence to BRE to verify the tool’s points scored in the Mat 01 Calculator. The LCA tool is then given its own tab in the calculator, which confirms the maximum score the tool can achieve, if used to its fullest extent. Items coloured green within the calculator are locked because they do not change when using the LCA tool. The items in blue should be edited by the design team to confirm the extent the tool has been used on the project. For RFO schemes, the assessment parts must also be selected. Items listed as ‘N’ in column W ‘Included in assessment?’ cannot be changed to a ‘Y’, as the LCA tool cannot be used for this element. For example internal doors cannot be assessed by the Green Guide. An element listed as ‘Y’ can be changed to a ‘N’ if the LCA tool has not been used for the element in the assessment. Column S confirms if the assessed building includes the element and should be included. For example if there are no stairs in the assessment, then this element is removed from the calculation by saying ‘N’ to cell S15 (in the green guide calculator).
12/01/2017 Reference to LCA approved tools updated.

Multiple buildings on the same site - KBCN0559

The areas of hard landscaping and boundary protection that need to be assessed on a site that contains several developments/buildings depends on the scope of works and scope of the assessment(s) being undertaken. Essentially, the areas that need to be assessed are all the areas of hard landscaping (as defined within the relevant definitions of the credit issue) and boundary protection within the construction zone (again defined within the relevant definitions) that are within the scope of works of the building under assessment. Therefore, if all buildings on one site are being assessed in one BREEAM assessment, then the hard landscaping and boundary protection related to all of these building's scope of works will need to be assessed. If there are several buildings with individual assessments and their own defined scope of works, then the hard landscaping and boundary protection applicable to the scope of works of each individual building will be assessed for each associated assessment. The assessment is concerned with the hard landscaping and boundary protection associated to the project under assessment, i.e. the areas under the control of the project under assessment. 

Option 1 scoring based on robustness and extent of LCA - KBCN0674

For Option 1, BRE Global verifies the LCA tool's score within the Mat 01 calculator based on the rigour of the life cycle assessment tool and the extent it is used on the assessment.  For this reason, as opposed to the UK New Construction schemes, the performance/scoring of building elements is not to be taken into consideration and Green Guide ratings for building elements are not linked to the scoring of the Mat 01 tool and credits achieved. Please see KBCN0237 for further details on using the calculator with verified LCA tools.

Option 2 – number of credits available - KBCN0963

When choosing to assess under option 2 'Elemental assessment of environmental performance information', the online tool allows 'All other buildings' and 'Industrial' assessments to achieve a maximum of four out of six and one out of two credits respectively. The exemplary credit is available for both options. This is to recognise that option 2 is a less detailed and extensive way to demonstrate compliance than option 1 'Project life cycle assessment study', for which the maximum score of six credits can be achieved.
03/04/2018 KBCN wording amended to clarify the maximum number of credits available for different building types.

Option 2 – Use of Green Guide to Specification - KBCN0964

As per the relevant Compliance Note, the Green Guide to Specification can be used to demonstrate compliance with Option 1, as the Green Guide is a compliant LCA tool. However, Option 2 is an elemental approach, for which the Green Guide cannot be used, as robust environmental performance information for the specific new element needs to be provided. The Green Guide to Specification only provides generic rating and for this reason it cannot be used to demonstrate compliance with Option 2 criteria.

Playground or other specialist surfaces - KBCN0694

Where the hard landscaping surface is specified to meet safety related performance (e.g. non-slip or soft surfaces for playgrounds) or particular performance related requirements (e.g. specialist sports performance surfaces such as astro-turf, netball courts and running tracks), then these surfaces can be omitted from the assessment. The standard specification of surfaces for multi-use areas (e.g. cement, tarmac, asphalt) must still be assessed.

Recycled materials in hard landscaping - KBCN0975

When recycled material is to be used for hard landscaping, the Green Guide rating will depend on whether the material comes from the same site or from another location. Typically, on-site recycled material is treated with very little impact, or ignored, as there is little or no energy/material input in putting it in place. When recycled material is brought in from elsewhere, transport, as well as any processing the material has gone through to make it fit for purpose, will be taken into account. If the assessor is in doubt, they need to submit a landscaping proforma along with any supporting documentation on the materials and their use and BRE will provide a rating and/or guidance.

Scope of hard landscaping - KBCN0634

For the purpose of assessment, hard landscaping includes (but is not limited to) parking areas (including manoeuvring areas, lanes, roads within the parking area), pedestrian walkways, paths, patios. The definition excludes basement parking, access or approach roads and designated vehicle manoeuvring areas, balconies, roof terraces,specialist sports areas (running tracks, netball areas etc.) and retaining walls.

The importance of EPDs - KBCN0895

The publishing of a third party verified EPD by a manufacturer indicates a transparent, robust and credible step in the pursuit and achievement of real sustainability in practice. While an EPD in itself is not proof that a product is sustainable, it is a public declaration of the environmental impacts associated with specified life cycle stages of that product.  A manufacturer or group of manufacturers, who carry out life cycle assessment (LCA) studies on their product(s) and publish the results in verified EPDs, help to create a knowledge base and an awareness of the environmental impacts quantified using standardised metrics. This allows benchmarking and the identification of improvement opportunities for the product’s environmental credentials. By implication, there are also opportunities for economic and social benefits to the manufacturer, such as the reduction in resource wastage through improvements in product design and manufacturing efficiency. The reward for EPDs in BREEAM schemes promotes the above, while encouraging designers, procurers and other stakeholders to make decisions on the basis of robust and credible environmental data. This is one of the markers of BRE’s strategic approach to the selection and procurement of construction materials and products. We recognise that there may be steep costs at the moment to small manufacturers wishing to publish verified EPDs for their products. This is a result of the maturity of the market and it is anticipated that as the awareness of the benefits of EPD increases, the increased uptake of EPDs will drive costs down.
Information correct as of 27thJanuary 2022. Please see for the latest compliance information.