Thermal breaks hinder or eliminate heat passing from one part of a structure to another where a differential exists between spaces. The main objectives of thermal bridging are to prevent condensation and lower energy loss. Critically, material choice can make a significant difference to the outcome of any intervention.
Here we consider various aspects of thermal bridging, including energy transfer and fire risk.
Why is a thermal break important?
Contemporary design and the regulations that govern them embrace the significance of conservation of energy and the need for occupant comfort. Advances in the science of materials and their manufacturing techniques have given rise to structural thermal breaks, which address the problems caused when building elements pass between areas where a temperature differential exists.
Evidence abounds about the effect on the building of poverty of detailing. Energy losses may have significant impacts on building performance—concerning the energy needed to raise or lower the temperature of a location and the financial and environmental costs.
In this regard, building regulations inform designers about minimum requirements for acceptable thermal performance. It is worth pointing out that energy loss is not the only downside to low thermal bridging; condensation and mould growth is another.
Applications of thermal breaks
It is possible to factor into any building detail, a calculable risk of thermal bridging, which often arises in conditions where there is a pronounced differential, such as in a warm server room or cupboard or in warm areas where the humidity is elevated (swimming baths and breweries are two good examples.
There are two main kinds of structural thermal breaks: Mechanical and solid-state. Mechanical includes situations where structural and compressive insulating elements combine as a means to adjust for thermal under-performance. Solid-State Thermal Break Plates, by contrast, may be observed in regular connections as ‘spacers.’
Energy depletion
Scientifically, every material may be assigned a value for heat conductivity. Every material has a value to indicate its thermal conductivity. In general, components with high-end structural properties also display low thermal conductivity. Such material must either be supplemented with more thermally useful materials to achieve acceptable levels of performance.
It is possible to calculate conductivity and adjust findings according to their intended environment. In this way, heat loss may be quantified for three types of elements: Plane, Linear, and Localised.
Condensation
Thermal transmission values assist in the calculation of likely performance. The greater the chance of detecting moist air, the greater the risk of moisture condensation, and all the problems that brings.
CE marking
Unfortunately, a European Standard does not exist to cover structural thermal breaks—therefore, no CE mark for thermal break products.
Materials testing
Manufacturing standards facilitate the comparison of a variety of materials through tests designed to be independent. New products give rise to new assessment standards. Currently, there are no specific standards for solid-state structural thermal break plates. It is, therefore, imperative that critical parts are subject to independent authentication.
There are many kinds of material testing. In general, they vary by the intended use of the product. This is important to designers because materials with apparently similar properties may perform quite differently in different real-life situations.
Design and thermal performance
The sole existing method for establishing the performance of point connections—known as Finite Element Analysis takes quite a bit of time and is complicated. And because there is little standardisation between building projects, details often vary significantly.
Current regulations demand assessing the risks of heat loss and condensation, to equivalent British and European Standards, and Building Research Establishment (BRE) reports.
Farrat structural thermal break plates can be successfully incorporated in most scenarios. Their flexibility offers designers more leeway to find appropriate solutions.
Carrying out comprehensive Finite Element Analysis requires consideration of both direct connections between materials and surrounding materials, which can also significantly impact outcomes.
Third-party BRE global certification can offer a competitive advantage over the competition. A database exists to give SAP 2016 access to the data.
These details apply to the following specific structures:
- storage facilities
- offices
- retail premises
- dwellings
- residential buildings
- Schools
- Sports halls
- Kitchens
A final SAP calculation at this stage is required to determine the thickest permissible break plate to ensure optimal performance.
Thermal break recommendations (principal checks)
Establish thermal break requirements. For optimal performance:
- Design in the littlest cross-sectional area of penetration of end connectors
- Use the least cross-sectional area of bolts
- Choose the thickest thermal break plate possible
- Select only materials with low thermal conductivity
- Place any thermal break connections in the building’s insulation.
Structural performance
The correct use of materials plays a critical role in performance, so make sure that you comply with manufacturers’ specifications in all cases. Also, take account of the material’s capacity for load dispersal from high-loaded points of a connection.
It’s a fact that material to material connections may torque under load. For this reason, make sure that the selected structural thermal break can deal with such loading. It would be best to avoid compromises over the short and long performance of connections with exceptional flexibility.
Fire performance
Tall buildings, since the Grenfell fire, now have much stricter requirements regarding building envelopes. Structural thermal breaks form no part of most recent Document B regulations, though they are a critical aspect of constructing tall structures’ fascia.
In common with most building materials, structural thermal breaks may be manufactured with various flammability and performance factors under fire loading. Designers discovering that the risk of fire in their construction is high should opt for fire-resistant material.
Deciding on the specification for structural thermal breaks is crucial. For this reason, endeavour to ensure that all performance criteria are known to all stakeholders. As a safeguard, ensure that the end product fully conforms by explicitly identifying manufacturers by name and product.
Mostly, thermal breaks feature in areas where fire protection is unnecessary. In cases where a fire rating is required:
- Apply a board fire-protection system
- Consider sprayed fire-protection (after checking compatibility)
- Design the connection assuming a total loss of thermal break material as the result of an accident.
Fire protection rules stipulate the amount of time afforded to occupants for escape and fire personnel for ingress. This is mostly down to the properties of materials that contribute to the fire load and easy combustibility or cause the fire to spread.
Chris Nicholls
Commercial Director
