A major factor in the performance of the building fabric is not simply the amount of insulation you install, but how it interconnects with other building materials and the other insulated elements within the design / installation.
Non-repeating (linear) thermal bridges are most commonly caused by discontinuities in the building envelope and can appear around openings such as windows and door openings, around loft hatches, rooflights, internal walls and floors junctions.
A thermal bridge or a cold bridge is an area of the building where there is a significantly higher heat transfer than the surrounding elements. Junction thermal bridges are measured linearly as psi values (Ψ-value – accumulated to make a Y-value) and they must be accounted for on all new build dwellings within SAP 10.2 and should be considered on all buildings (new or retrofit) to mitigate the heat loss through these bridges. A Y-value represents the sum of the total non-repeating thermal bridges, and these are added to the fabric performance within SAP as a penalty.
It has been estimated that up to 30% of the heat loss in a well-insulated building is through these “non-repeating thermal bridges”. It is critical when calculating the performance of low energy buildings that heat loss is measure and minimised. Thermal bridges in retrofit should also be considered when adding insulation to the fabric elements to mitigate the bridges.
Here at Unilin Insulation we can assist with the mitigation of the thermal bridges with the expertise within our technical department and our extensive range of psi values in our library.
KEY POINTS
• Continuity of insulation is key.
• Identify the bridges as early as possible so you can mitigate to ensure the building performs to the standard it should.
• Liaise with a specialist / locate certified psi value details to ensure that you put the right measures in place.
• Follow the detail as designed onsite: the devil is in the detail.
Below is a link to our video explaining thermal bridging.
What is a thermal bridge?
To make it simpler, think of a thermal bridge as a "heat leak" or a "hot or cold spot" in your home's insulation. It's like having a tiny gap or weak point in the protective layer that lets heat flow in or out more easily than the surrounding areas.
These thermal bridges can lead to energy loss, higher heating or cooling bills, and sometimes even uncomfortable spots in your home where you feel colder or warmer than the rest of the space. Properly identifying and addressing these thermal bridges is essential to maintain a more comfortable and energy-efficient home. Where thermal bridges exist there’s also more chance of moisture problems leading to damp and mould.
With thanks to Martyn Randall of Unilin insulation for pulling this short piece together. Martyn is a qualified retrofit coordinator, overheating assessor and the specification manager for the Southern UK for Unilin.