Around 30% of the total heat loss through a building’s fabric can be as a result of thermal bridging. And research shows that a dwelling’s annual CO2 emissions can be reduced by up to 10% with better detailing.
SAP2005 accounts for heat losses through “non-repeating thermal bridges” within building construction, such as lintels and door jambs, separately from “repeating thermal bridges” such as timber studs or mortar joints, which are accounted for within standard U-value calculations.
Values for these non-repeating bridges known as Lineal Thermal Transmittance need to be entered into the software by the SAP assessor.
When designing to meet the current energy efficiency standards the use of Accredited Details is a significant tool in helping the designer achieve the required objectives, however when trying to achieve higher standards eg when aiming for Code 3 and above the significance of reducing heat loss through these non-repeating thermal bridges becomes critical and the use of the Accredited Details alone are not sufficient.
When designing for Code 3 and above it is necessary incorporate the “Enhanced Construction Details” as produced by The Energy Saving Trust alongside the Accredited Details. This can improve on the performance of the Accredited Details by over 85%. and enables the SAP Assessor to input compliant values.
