In Flanders (the other Belgian Regions are expected to follow shortly) from 1 January 2011 the EPB reporter must allow for the impact of nodes on the K-level for new buildings subject to a planning permit application or a report.

The compulsory method for determining the impact of nodes on the transmission heat loss coeffi cient is laid down in appendix VIII “Behandeling van bouwknopen” in Belgisch Staatsblad/ Moniteur belge (08.12.2010). Three methods are provided: a detailed method (Option A), a method of EPB-accepted nodes (Option B) and a method in which a fi xed penalty is placed on the K-level (Option C).

Numerical calculations with validated soft ware (Option A) are very labour-intensive and demand specialised know-how and soft ware. If no eff ort is made to limit heat loss at the nodes (Option C) the unknown impact of the nodes on the total heat loss is established by means of a fi xed penalty on the K-level of 10 K-points. In practice, as research has shown, Option B will most oft en be chosen.

It is important to note that, like the other options, Option C in no way absolves the building team from the responsibility to minimise the risk of mould growth and condensation.

In Option B, a fi xed K-level penalty of 3 K- points is allocated for ‘EPB-accepted nodes’. These are nodes whose specifi c features do not cause improper heat loss and that can therefore be considered as nodes with low thermal conductivity. No lengths and/or quantities need to be established for these nodes, which means that calculations can be limited. Option B proposes two ways for ensuring a node is ‘EPB-accepted’:
The node complies with the applicable limit values.
The node satisfi es one of the three basic rules for thermal bridge features.

Research has shown that more than 50% of all designers prefer to work with Option B and Basic Rule 2 (Insertion of insulating parts).