H+H - Int

Heat losses through repeating thermal bridges, such as insulation bridged by cavity wall ties or stud framing, within a structure are accounted for by the calculation of the U-value of the plain element in question.

Thermal bridges also exist at junctions between elements (e.g., walls/floors, corners etc). Additional heat losses associated with these thermal bridges are required to be accounted for in SAP2005, which in Appendix K gives a procedure based on a linear thermal transmittance value, ψ (Greek letter Psi – pronounced "si").

The ψ factor is a property of the thermal bridge junction and is the rate of heat flow per unit length of the thermal bridge. Table K1 of SAP2005 gives values of ψ applicable to different types of junctions detailed in accordance with the accredited Construction Details (ACDs). The additional heat loss at each junction is given by multiplying the linear length of the junction by the appropriate ψ from Table K1, the summation of which will give the total heat loss due to thermal bridging (HTB) for the dwelling which is then added to the other heat losses in SAP.

H+H aircrete can be used to allow an enhance y – value of 0.04 to be used (effectively having heat losses at non repeating thermal bridges) without significantly changing existing construction details.

Changes to Part L of Building Regulations were issued in October 2010 and changed the way in which the y value is calculated.  A report, commissioned by the Aircrete Products Association (APA) shows that, even with the changes, Aircrete will continue to give a value of 0.04.

The H+H Thermal Compliance Guide also provides valuable information on the new Part L regulations with lots of practical guidance.

For more information on Thermal Linear Bridging, how it will affect your building or to obtain a copy of the APA Report, please contact our Technical team on 01732 880580.

To determine the products and applications we have available, follow the links on the Left hand panel or follow the Library link to download information on our products and services.

For more information please call 01732 886444 or email info@hhcelcon.co.uk.