Farrat Structural Thermal Break Plates/Pads are high performance thermal insulators used between horizontal and vertical connections of internal and external elements to prevent thermal or cold bridging.
Structural Thermal Breaks provide a simple, economical and extremely effective solution to meeting Part L of the Building Regulations by way of reducing heat loss and the risk of internal condensation. Farrat Structural Thermal Breaks have British Board of Agrement Certification [BBA]. This is important in a market where there are materials offered which have not had independent evaluation to ensure suitability in structural connections.
Farrat Structural Thermal Breaks also meet the NHBC’s technical requirements.
Changing Legislation in response to climate change and energy saving has meant that Farrat now supply Structural Thermal Break Plates for the UK and overseas market.
Constantly driven by engineering excellence, we continue to lead the way in the development of the Structural Thermal Break Plate market with the following Certifications and membership:
Farrat Structural Thermal Breaks have British Board of Agrèment Certification [BBA].
Farrat Structural Thermal Breaks meet the NHBC’s Technical Requirements. This is referenced in the BBA Certification.
Farrat is a member of BRE’s Certified Thermal Details and Products Scheme.
Farrat Structural Thermal Breaks can be found on NBS Plus and NBS National BIM Toolkit and Library.
Farrat operates under an ISO 9001:2008 Quality Assurance System. This also incorporates BBA’s Product Quality Plan.
Farrat operates under an ISO 14001:2004 Environmental Management System.
Farrat is a member of The Steel Construction Institute [SCI].
Farrat Structural Thermal Breaks are manufactured from high performance materials. We only use materials specifically developed for use within the building envelope and have British Board of Agrement Certification [BBA] to ensure that designers and clients have confidence in the product which is used in structural connections. Every order is accompanied with a Certificate of Conformance.
We offer two grades, Farrat TBK and Farrat TBL.
|Farrat TBK||Farrat TBL|
|Characteristic Compressive Strength, fck (N/mm² , MPa)||312||89|
|Design Value for Compressive Strength, fcd (N/mm² , MPa)||250||70|
|Elastic Modulus (N/mm² , MPa)||4100||2586|
|Water Absorption (%)||0.14||0.48|
|Thermal Conductivity (W/m-k)||0.187||0.292|
|Colour (may vary)||Amber||Black|
|Thicknesses available (mm) +||5, 10 ,15 ,20 & 25||5, 10 ,15 ,20 & 25|
|Thickness Tolerances (mm) ++||0 to +0.3||0 to + 0.25 (TBL5)
+0.2 to +1.5 (TBL10)
+0.3 to +2.5 (15, 20 & 25)
|Maximum sheet size (mm)||2400 x 1200||2500 x 1250|
|+||Multiple plates can be provided for applications where thicknesses greater than 25mm are required. Both materials can be supplied in non-standard thicknesses (please contact Farrat for further details).|
|++||Farrat TBL can be supplied to tighter tolerances (please contact Farrat for further details).|
For further details, please refer to our Structural Thermal Breaks brochure.
There are few standard construction details between projects therefore detailing of the building envelope and penetrations can vary significantly. As a result, the calculation of thermal performance and compliance with requirements can be complex.
There are two aspects to the thermal performance of the building envelope; heat loss and condensation risk. Both issues are covered by Building Regulations and guidance on meeting them is provided in various Approved Documents (England and Wales), Technical Handbooks (Scotland) or Technical Booklets (Northern Ireland). These documents currently require heat loss and condensation risk to be assessed in accordance with the same British Standards, European Standards and BRE Publications.
Unlike proprietary mechanical thermal break systems, the plate type thermal break is very simple to incorporate into most details. This flexibility means that it can be used for a wider variety of applications and is not restricted by the modular nature or the space required for proprietary mechanical systems. This flexibility also provides the Designer with greater freedom to develop a bespoke solution.
Thermal Design Considerations:
How thick does the thermal break need to be?
Ideally the detail should be thermally modelled. This requires not only the members and connections, but the entire fabric of the envelope local to the connection to be included in the model. This applies to both mechanical and plate type thermal breaks.
This issue is often forgotten or considered late in the construction process and due to the cost and time implications, modelling is often not undertaken. However, modelling should be considered where:
- the environmental conditions pose a greater risk (e.g. swimming pools)
- the detailing of the planar elements local to the connection are considered to have an inferior thermal performance to that of the main building envelope
- there is significant repetition of the same detail (e.g. balconies).
If thermal modelling is not undertaken, the following should be considered:
- The thermal break should be located within the insulated zone of the building envelope.
- Selection of the thickest thermal break (up to 25mm) considering cost, thermal performance and structural requirements (limitations).
- Minimisation of the cross sectional area/ mass of the steelwork penetrating the building envelope where possible.
- The performance of the connection detail against the BRE’s Certified Farrat details – information provided below.
Stainless steel bolts are sometimes specified for durability reasons. Isolation using normal methods may need to be considered because of bi-metallic action and corrosion. Isolation using thermal washers and thermal bushes will provide minimal additional thermal performance.
Point thermal bridge
The quantity which describes the heat loss associated with a single penetration is a point thermal bridge(χ-value, W/K). This is pronounced as ‘chi-value’. This is a property of the thermal bridge and is the rate of heat flow per penetration that is not accounted for in the U-values of the plane building elements containing the point thermal bridge.
Linear thermal bridge
The quantity which describes the heat loss associated with a thermal bridge is its linear thermal transmittance (Ψ-value, W/m·K). This is pronounced as ‘psi-value’. This is a property of a thermal bridge and is the rate of heat flow per degree per unit length of the bridge that is not accounted for in the U values of the plane building elements containing the linear thermal bridge.
The Specifier will usually identify indoor and outdoor temperatures and relative humidity conditions under which condensation must not occur. Guidance on suitable conditions is given in BS 5250 Code of Practice for the Control of Condensation in Buildings. From these conditions it is possible to determine the allowable minimum temperature on the construction detail below which there would be a risk of condensation. Finite Element Analysis and similar analysis methods allow the temperature distribution to be predicted.
The temperature factor (f) is used to assess the risk of surface condensation or mould growth and is calculated under steady state conditions. To avoid problems of surface condensation or mould growth, the fRsi should not be less than a critical temperature factor (fCRsi).
A range of appropriate critical temperature factors are identified in BRE Information Paper IP 1/06 and listed below:
|Building type||Critical Temperature Factor (fCRsi)|
|office, retail premises||0.50|
|dwellings, residential buildings, schools||0.75|
|sports halls, kitchens, canteens||0.80|
|swimming pools, laundries, breweries|
BRE Certified Thermal Products Scheme
Farrat is a member of BRE’s Certified Thermal Details and Product Scheme.
The scheme database includes for both BRE Certified Thermal Details and Products and Government Accredited Details, and this provides a freely accessible and independently assessed and certified resource for users. The third-party BRE Global certification can distinguish products and services from their competitors, and give customers confidence about the thermal performance of the products.
- storage buildings
- retail premises
- residential buildings
- schools and sports halls
- kitchens and canteens
- swimming pools
Thermal Modelling Specialists
Graeme A. Hannah (MEng) – Technical Manager
BRE Certified Thermal Details and Products Scheme
T: +44 (0) 1355 576 000 E: email@example.com
Annalisa Simonella – Director
Loud1 Design | Building Physics
T: +44 (0)7906 082 828 E: firstname.lastname@example.org
Dr. Richard Harris – Partner, Consultancy Department
T: +44 (0)20 7565 7066 E: email@example.com
- Thermal bridge in a link without a Farrat Thermal Break. The temperature of the steel is on the hot side of the outer-wall system (9.8°C) and heat loss (χ value) is 1,31W / K.
- Distribution of temperature with Farrat Structural Thermal Break plate (TBK). The temperature on the hot side of the facade system has been improved to 16.5°C and the heat loss is limited to 0.35 W/K = 73% less heat loss.
Under the SCI Assessed Product Scheme the technical data and structural design methodology for Farrat Structural Thermal Breaks has been independently verified by the SCI. The design considerations are set out in the Farrat Structural Thermal Breaks Connections Guide.
Unlike proprietary mechanical thermal break systems, the plate type thermal break is very simple to incorporate into most details. This flexibility means that it can be used for a wider variety of applications and is not restricted by the modular nature or the space required for proprietary mechanical systems. This flexibility also provides the designer with greater freedom to develop a bespoke solution.
Structural Design Summary (steel connections)
Connections that include thermal break plates should be designed in accordance with the relevant design standards (e.g. BS EN 1993-1-8) or industry guidance (e.g. SCI publications). The following additional checks should also be undertaken, check that:
- the thermal break plate can resist the applied compression forces.
- any additional rotation due to the compression of the thermal break plate (including allowance for long term creep) is acceptable.
- the shear resistance of the bolts is acceptable given that there may be a reduction in resistance due to:
- PACKS – Clause 188.8.131.52 of BS 5950-1 or clause 3.6.1(12) of BS EN 1993-1-8
- LARGE GRIP LENGTHS – Clause 184.108.40.206 of BS 5950-1 or BS EN 1993-1-8
Structural Design Considerations:
Thermal break plates are contained within the protective envelope of the building and in general Building Regulations do not require them to be fire protected or have a fire performance rating. Where the connection containing the thermal break requires fire protection then the following options can be considered:
|Board Protection||A number of proprietary fire protection board systems are available on the market.|
|Sprayed Fire protection||A number of proprietary sprayed fire protection systems are available on the market. The manufacturer should be consulted regarding the compatibility between the system and the thermal break materials. Alternatively consideration can be given to recessing the thermal break and providing a continuous fire protection strip (Nullifire etc.)|
The majority of thermal break connections are related to secondary elements only.
The Structural Engineer will consider robustness during the design process and will refer to local codes and standards. Where a thermal break is located within a key critical element this may need further analysis leading to either consideration of the complete loss of the thermal break or inclusion, for example, of a physical “fail safe”. The detailing of this can often be undertaken whilst maintaining the thermal performance of the connection.
Handling on site
Thermal breaks are normally procured by the steel fabricator as part of the steel frame package on a project. The delivery from Farrat is normally co-ordinated with the steel work contractor erection schedule. They are delivered to site with each one labelled with a unique reference linked to the steel work contractors drawings.
For identification purposes Farrat TBK and TBL are different in colour. If it is essential to the project that both materials are used on the same project, Farrat normally advise that the connection arrangement (e.g. bolt positions) is unique to ensure that no errors are made during installation. This is in addition to Farrat’s normal labeling protocol.
The general handling requirements for thermal breaks should be in line with other component accessories expected to be handled with the primary steel work. This is covered in the NSSS: Section 8 Workmanship – Erection. The NSSS also sets out the requirements of the Quality Management System expected to be adopted by all competent steelwork contractors working on UK construction projects.
- Structural Thermal Break Plate (TBK) with 4-hole connection, steel-to-steel.
Farrat Structural Thermal Breaks can be used in a wide variety of applications where there is a structural requirement of the thermal insulation:
- Steel to steel
- Steel to concrete / masonry
- Steel to timber
- Concrete to concrete
- Facade system connections to the primary frame
- Brise Solei and Canopies
- Roof plant room columns
- Connections of external to internal primary building elements
- Isolation of sub-structure & basement structure elements
- External staircases or external balconies
- Man-safe systems
- BMU Systems
- Connections to existing structures
Farrat’s market leading Structural Thermal Break Plates & Pads (FTB) are high performance thermal insulators, used between horizontal and vertical connections of internal and external elements to prevent thermal/cold bridging.
- Mechanical properties of the materials aligned for building applications
- High or very high strength options
- Low thermal conductivity (k)
- Ability to be manufactured in 2D or 3D (i.e. recess, chamfer, etc.)
- Variety of thicknesses available. Special thickness/tolerances available to specifiers
- British Board of Agrement Certification [BBA]
- A simple and effective solution to meeting Building Regulations
- Not a proprietary modular mechanical system – so offers the designer scope to develop bespoke connection detailing
- Supported by technically qualified staff
- Supported by external organisations including BBA, NHBC, NBS and BRE.
- Manufactured under Farrat’s ISO9001 & ISO14001 Systems
- Manufacturing capacity allowing us to meet your lead time
Should show a fully detailed connection or one communicating the design intent with a supporting specification (NBS or similar).
Is normally responsible for ensuring that the connection meets the requirements of the Building Regulations Part L (SAP).
Design Output – Thermal performance/ Thickness (Farrat TBK or Farrat TBL).
The Structural Engineer
Is normally responsible for designing the connection or providing a performance specification for the steel work fabricator.
Design Output – Strength (Farrat TBK or Farrat TBL)
Sample Specification for project using Farrat TBK – National Building Specification (NBS)
NBS Clause: G10/ 350 Structural Thermal Break Connection Plate
- Manufacturer: Farrat Isolevel Ltd, Balmoral Road, Altrincham, Cheshire, WA15 8HJ, Tel: +44 (0)161 924 1600, Fax: +44 (0)161 924 1616 www.farrat.com
- Product Reference: Farrat TBK
- Thickness: 25 mm
- Plate Size: As Drawing number – or to be determined by the connection designer
- Hole Size & Positions: As Drawing number – or to be determined by the connection designer
- Certification – BBA
Please be aware there are cheaper materials on the market that the supply chain may provide as an alternative, but in our view not of equal performance or certificated for use in building applications (structural).
To enable us to provide a quotation, we will require the following information for each plate:
- Material – Farrat TBK or Farrat TBL
- Plate Dimensions
- Plate Thickness
- Size and Number of Holes
- Any Special Requirements
- Delivery Location
To accept orders, our manufacturing facility will require a fully dimensioned drawing with each plate type having a unique customer reference (drawing number).
We aim to start manufacturing within 3 working days of receiving the order and you will be advised of a despatch date.
We can very often start manufacturing sooner, and can work with you on very large orders to meet your programme and requirements.
- Each plate has a label attached [Farrat/BBA]
- Each order will be accompanied by a Certificate of Conformance under our British Board of Agrement Certification.
QMU Graduate Centre
Type: TBK Thermal Breaks
Type: Structural Thermal Breaks
Type: Structural Thermal Breaks
AIRC Cranfield University
Type: TBK Thermal Breaks
Nottingham Trent University
Type: TBL Thermal Breaks
To provide a quotation please submit the following information:
- Material Type – Farrat TBK or Farrat TBL
- Plate Dimensions & Thickness
- Size & Number of Holes*
- Delivery Postcode
We aim to start manufacturing within 3 working days from an order being placed.
*A fully dimensioned drawing will be required for each type of plate with a unique reference prior to fabrication.
Stephen Blundell BEng(Hons) CEng MICE MIStructE
Technical Director – Structural Thermal Breaks
DD: +44 (0)161 924 1600
Structural Thermal Break Connections
Stephen is a Chartered Engineer with over 35 years experience in civil and structural engineering. As Technical Director for Structural Thermal Break Connections at Farrat, Stephen is the technical lead for thermal break systems and specification.