You are here: 9.0 Materials > Mat 04 Insulation

Mat 04 Insulation

Number of credits available Minimum standards
2 No


To recognise and encourage the use of thermal insulation which has a low embodied environmental impact relative to its thermal properties and has been responsibly sourced.

Assessment Criteria

This issue is split into three parts;

The following is required to demonstrate compliance for:


  1. Any new insulation specified for use within the following building elements must be assessed:
    1. External walls
    2. Ground floor
    3. Roof
    4. Building services

Embodied impact

One credit

  1. The Green Guide rating for the thermal insulation materials must be determined. Green Guide ratings for thermal insulation can be found at: (please refer to the Compliance notes for guidance where specific insulation has been assessed within an element for BREEAM issue Mat 01).
  2. The Insulation Index for the building insulation is the same as or greater than 2.
  3. The Insulation Index is calculated using the BREEAM Mat 04 calculator which uses the following calculation methodology:

    For each type of thermal insulation used in the relevant building elements, the volume weighted thermal resistance provided by each type of insulation is calculated as follows:

    1. (Area of insulation (m2) x thickness(m))/Thermal Conductivity (W/ m.K) OR
    2. Total volume of insulation used (m3)/Thermal conductivity (W/m.K)

The volume weighted thermal resistance for each insulation material is then multiplied by the relevant Green Guide point(s) from the following table to give the Green Guide Rating corrected value:

Table 26 Green Guide rating points/element

Green Guide Rating Points/element
A+ 3
A 2
B 1
C 0.5
D 0.25
E 0

To calculate the Insulation Index, the sum of the Green Guide rating corrected values for all insulating elements is divided by the sum of the volume weighted thermal resistance values (an example calculation is provided in the Additional Information section).

Note: Where an independently verified third-party Environmental Product Declaration (EPD), covering part of or the whole life cycle, is available for an insulating material/product, this can be used to increase the contribution of that material/product to the building’s Mat 04 performance (for more detail refer to the Calculation procedures in the Additional Information section).

Responsible sourcing

One credit

  1. At least 80% by volume of the thermal insulation used in the building elements identified in Item 1 must be responsibly sourced i.e. each insulation product must be certified in accordance with either tier levels 1, 2, 3, 4, 5 or 6 as described in BREEAM issue Mat 03. The table below shows the key processes and supply chain processes required for common insulation products.

Table 27 EMS criteria for insulation products

Material Key Process Supply chain processes
Foam Insulation Insulation manufacture Main polymer production, e.g. Polystyrene, MDI, Phenolic resin or equivalent
Stone wool, glass & cellular glass made using < 50% recycled input Product manufacture Any quarried or mined mineral over 20% of input
Wool Product manufacture Wool scouring
Products using > 50% recycled content except those using timber Product manufacture Recycled content by default
Timber-based insulation materials including those using recycled timber Product manufacture Recycled timber by default, all other timber from one of the recognised timber certification schemes in BREEAM issue Mat 03.
Other renewable-based insulation materials using agricultural by-products (e.g. straw) Product manufacture By-product manufacture by default
Any other product Product manufacture 1 or 2 main inputs with significant production or extraction impacts should be identified

Compliance Notes





Shell only

It is envisaged that the majority (80%+) of fabric/services insulation will be specified/installed in the shell and core building. Where the shell only developer is not installing the majority of insulation, compliance with this BREEAM issue for the tenanted areas of the building can be demonstrated via one of the following means:

  1. Option 1 – Use of a tenancy lease agreement between the developer and tenant/s (full value of available credits)
  2. Option 2 – A Green Building Guide for tenant fit outs (half the value of the available credits)
  3. Option 3 – Developer/Tenant collaboration (full value of available credits)

Refer to Appendix D – BREEAM New Construction and shell and core/speculative assessments of this Scheme Document for further description of the above options.


Insulation incorporated as part of an off-site manufactured element If the insulation is incorporated as a component of an element that has been manufactured offsite (in order to maximise material optimisation) e.g. a wall or roof, and that element has been assessed as part of Mat 01, then for the purpose of assessing the insulation for this BREEAM issue, a Green Guide rating of A+ should be used. The same rule applies to insulation that has a significant additional function, such as providing supporting structure e.g. structural insulated panels (SIPS). In the Green Guide the actual insulation will be listed within the element title, rather than under the generic insulation category.


Awarding credits Both credits can be awarded independently of each other - i.e. it is not a requirement of the second credit that the first is achieved, and vice-versa.


Element consisting of more than one insulation type See criterion 4 Where more than one insulation type is present for a given element, the rating, area and conductivity for each insulation type should be entered into the BREEAM Mat 04 calculator and an average is calculated (by volume).


Finding exact Green Guide Ratings See criterion 2 Where no similar insulation can be found assessors should seek guidance from BRE on the appropriate rating.


Environmental Profile Certification of products Mat 01 Life cycle impacts Compliance Notes.

Schedule of Evidence

Ref Design stage
Post-construction stage

Design drawings AND/OR relevant section/clauses of the building specification or contract confirming:

  1. The location of insulating materials.
  2. The area (m2) and thickness (m) or volume (m3) of insulation specified.

Manufacturer’s technical details confirming the thickness and thermal conductivity of the insulating materials specified.

A copy of the output from the BREEAM Mat 04 calculator.

The Green Guide rating and element number for the assessed insulation specifications.

And if relevant:

  1. Copies of Environmental Product Declarations
  2. A link/reference to the EPD’s Product Category Rules
  3. Online Green Guide calculator output
  4. Environmental Profile certificate(s) (or certificate number)

'As built' drawings and, where relevant, written design team confirmation of any changes to the materials specification.

5 Evidence as outlined in BREEAM issue Mat 03 confirming compliance for the insulating materials. Evidence as outlined in BREEAM issue Mat 03 confirming compliance for the insulating materials.

Additional Information

Relevant definitions

Environmental Product Declaration
Mat 01 Life cycle impacts
Green Guide
Mat 01 Life cycle impacts
Green Guide Element Number
Mat 01 Life cycle impacts
Insulation Index
A measure of performance used in BREEAM that seeks to assess the thermal properties of insulation products used in the building relevant to the embodied impact of that insulating material.
BREEAM Mat 04 calculator
A spreadsheet based tool used by the BREEAM assessor to determine the Insulation Index and therefore, whether the BREEAM credit is achieved.
Materials optimisation
Material optimisation means adopting a resource efficient approach to design which results in less material being used in the design (i.e. lean design), and/or less waste is produced in the construction process, without compromising the design concept. Whilst this assessment issue is focused on the embodied impact and sourcing of the insulation material specified, the design team should consider solutions that optimise the use of the material and therefore minimise construction waste.

Checklists and Tables


Calculation procedures

Example calculation as carried out by the BREEAM Mat 04 calculator

The Insulation Index is calculated for a building using the following types of insulation:

Type 1 Walls

Area = 450m2. Thermal insulation thickness = 100mm. Thermal conductivity = 0.023 W/mK Green Guide rating = A (2 points)

Volume weighted thermal resistance: ((450x0.100)/0.023) = 1956

Green Guide rating correction: 1956 x 2.0 = 3912

Type 2 Building Services

Volume of insulation used = 21m3. Thermal conductivity = 0.022 W/mK

Green Guide rating = C (0.5 points)

Volume weighted thermal resistance: (21/0.022) = 955

Green Guide rating correction: 955 x 0.5 = 477

Type 3 Roof

Area = 210m2. Thermal insulation thickness = 120mm. Thermal conductivity = 0.027 W/mK Green Guide rating = A+ (3 points)

Volume weighted thermal resistance: ((210x0.120)/0.027) = 933

Green Guide rating correction: 933 x 3.0 = 2799

Type 4 Ground Floor

Area = 210m2. Thermal insulation thickness = 120mm. Thermal conductivity = 0.027 W/mK Green Guide rating = B (1 point)

Volume weighted thermal resistance: ((210x0.120)/0.027) = 933

Green Guide rating correction: 933 x 1.0 = 933

Total volume weighted thermal resistance = 1956+955+933+933 = 4777

Green Guide rating correction = 3912 + 477 + 2799 +933 = 8121

Insulation Index: Green Guide Rating Correction/Total volume weighted thermal resistance = 8121/4777 = 1.7 (credit not achieved)

Calculation Procedure where a specific Environmental Product Declaration is available for a material

Please refer to the Calculation procedures in BREEAM issue Mat 01. Note, step 1 of the Calculation procedure outlined in BREEAM issue Mat 01 (the proportion of the total environmental impact of the assessed element) is not applicable for this issue as the insulation is assessed as a single material in BREEAM issue Mat 04 and not as part of a larger building element containing other materials (as in BREEAM issue Mat 01).

Other information