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Mat 04 Insulation

Number of credits available	Minimum standards
1	No

Aim

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

Assessment criteria

The following is required to demonstrate compliance:

One credit - Embodied impact

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.

The Insulation Index for the building fabric and services insulation is the same as or greater than 2.5. See the Mat 04 Insulation section for a description of calculating the Insulation Index.

Checklists and tables

None.

Compliance notes

Ref	Terms	Description
Shell and core
CN1	Applicable assessment criteria	Embodied impact - criteria 1 to 2 Both options: All new insulating products being specified or installed by the developer must be accounted for in the assessment of this issue. Refer to Appendix D – BREEAM UK New Construction and Shell and Core Project Assessments for a more detailed description of the above shell and core assessment options.
Simple buildings
CN2	Applicable assessment criteria	All criteria relevant to building type and function apply.
General
CN3	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 off-site (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.

Methodology

Insulation Index calculation

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:

(Area of insulation (m²) x thickness (m))/thermal conductivity (W/m.K) OR
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 49 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. See example calculation below.

Note

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).
Where no similar insulation can be found assessors should seek guidance from BRE on the appropriate rating.
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. See below for more details.

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 = 0.023W/mK
Green Guide rating = A (2 points)

Volume weighted thermal resistance: ((450 x 0.100)/ 0.023) = 1956

Green Guide rating correction: 1956 x 2 = 3912

Type 2 Building services

Volume of insulation used = 21m³
Thermal conductivity = 0.022W/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 = 0.027W/mK
Green Guide rating = A+ (3 points)

Volume weighted thermal resistance: ((210 x 0.120)/ 0.027) = 933

Green Guide rating correction: 933 x 3 = 2799

Type 4 Ground floor

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

Volume weighted thermal resistance: ((210 x 0.120)/ 0.027) = 933

Green Guide rating correction: 933 x 1 = 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 Mat 01 Life cycle impacts – Methodology

Note: Step 1 of the methodology 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).

Evidence

Criteria	Interim design stage	Final post construction stage
All	One or more of the appropriate evidence types listed in The BREEAM evidential requirements section can be used to demonstrate compliance with these criteria.
All	A completed copy of the Mat 04 Calculator tool	As per interim design stage

Additional information

Relevant definitions

Environmental Product Declaration: Refer to Mat 01 Life cycle impacts
Green Guide: Refer to Mat 01 Life cycle impacts
Green Guide element number: Refer to 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. While this assessment issue is focused on the embodied impact of the insulation material specified, the design team should consider solutions that optimise the use of the material and therefore minimise construction waste. See Mat 06 Material efficiency for more information.

Other information

None.