• MenuMenu
  • Home
Thermal Bridging

A requirement of SAP Assessments is to calculate thermal bridging lengths

Thermal Bridging Modelling using 2d and 3d software to simulate the extra heat loss through junctions known as its psi value.

Thermal Bridging

SAP accounts for heat lost through non-repeating thermal bridges such as lintels and door jams, separately from that lost through repeating thermal bridges within the building's thermal elements, such as timber studs or mortar joints. These are accounted for in standard wall U-value calculations.

A requirement of SAP 2012 is that thermal bridging lengths are entered for each non-repeating thermal bridging, such as lintels, corners and eaves. Where we are provided the thermal bridging value (PSI) from the client we will calculated the lengths and enter them into the SAP Calculations. Unlike some of our competitive we include this service as a complimentary as part of the SAP.

If you are using a thermal block such as Thermalite or Celcon we recommend using the Constructive Details.

Where non standard junctions are being specified we can calculate the specific PSI value using 2d and 3d modelling software as required to model the heat loss at the junction to determine any extra heat loss as a result of the junction details.

A thermal bridge occurs at the part of the building envelope where the otherwise uniform thermal resistance is significantly changed by:

  • Full or partial penetration of the building envelope by materials with a different thermal conductivity and/or
  • A change in thickness of the fabric and / or
  • A difference between internal and external areas, such as those occurring at wall/floors/ceiling junctions.


> Download Thermal Bridge Sheet

Heat flow is generally greater at junctions, and therefore this is often where the lowest temperatures on a surface occur. Therefore, the Frsi value is normally calculated using the temperature occurring at the internal intersection of the two constructions as this is lower than the surface temperature on the plane elements.

As internal surface temperature is a property of the construction, so too is the risk of mould growth and surface condensation risk. A more insulated construction will have a higher internal surface temperature and the risk of mould growth occurrence will be lower. The actual risk of condensation is dependent on the internal temperatures and external temperatures for the building as well as the relative humidity levels at those temperatures.

Why not ask us for a quote?

We have extremely competitive pricing, why not get a free non-commital quote.


Ready for a quote?

We have extremely competitive pricing, why not get a free non-commital quote. Call us on 01962 718870 or use the link below.


Why choose Sadler Energy for your next construction project?

There must be a reason why our clients keep coming back to us.

On Time

On Budget


Great Ideas


Happy Clients

© Sadler Energy and Environmental Services Ltd.
[Site Map] [Privacy] [Environmental Policy]

SAPs • Code For Sustainable Homes • EPCs • Air Testing
Covering Southern England: Hampshire, Dorset, Sussex, Wiltshire, Berkshire, Surrey and London.

Cookies Notice

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we'll assume that you are happy to receive all cookies on the Sadler Energy website. However, if you would like to, you can change your cookie settings at any time.

AllowMore Information