November 2022

Ask The A. Proctor Group
THERMAL BRIDGES AND ENSURING
BUILDINGS PERFORM AS DESIGNED
In the latest article in our series about some commonly held myths for contractors
concerning thermal and acoustic insulation, condensation control and fire protection, the
experts at The A. Proctor Group tackle the question: Is it true that the odd cold bridge is
not a problem and insulating reveals doesn’t make much difference?
Why a cold bridge / thermal bridge
matters
Acold bridge, more commonly referred to as
a thermal bridge, will result in additional
heat loss through a conductive part of the
building envelope that needs to be included in the
building’s energy assessment calculation. The
heat loss caused as a direct result of thermal
bridging will lead to increased energy costs for
buildings and homes. It is estimated that thermal
bridges can account for 20-30% of the heat
loss in new build houses. The drive to
improve the insulation of homes
will result in thermal bridging
becoming even more
significant. In addition,
thermal bridging can lead to
Left: Spacetherm Blanket from The A. Proctor Group. Above: Spacetherm Multi consists of Spacetherm
Aerogel insulation blanket bonded to a 6mm Magnesium Oxide Board.
cold spots, adding to the risk of
condensation and the potential for
mould growth.
Where thermal bridges are found
Within the construction of buildings, there are
typically two types of thermal bridges which can
occur:
• Repeating
Non-repeating thermal bridges
typically occur at junctions where
walls and floors penetrate the thermal
envelope, around windows and doors, and steel
lintels connecting the internal and external walls.
These require more complex calculations and
cannot be accounted for in the U-value but will be
accounted for by the PSI-value or Y-value (Ψ).
Thermal bridges also commonly occur due to air
non-dwellings. New build homes are to be
assessed under a new Standard Assessment
Procedure (SAP10.2) calculation. SAP10.2
stipulates increased insulation requirements and
new targets for the TER (Target Emissions Rate)
calculations. SBEM will continue to be used for
non-residential dwellings.
Identifying where cold bridging exists or the risk
of thermal bridging can be achieved using
• Non-Repeating
gaps or penetrations through the insulation layer thermal imaging. The A. Proctor Group provides
and between the external and internal structures. comprehensive technical support – including
A repeating thermal bridge will occur where
poorer insulating materials intersect other layers
of insulation within the building fabric. Examples
include timber or steel studs in framed
construction, at the point of wall ties, or the mortar
joints of insulated walls and balconies. The differing
heat flow due to a repeating thermal bridge can be
accounted for in the U-value calculation.
So air leakage is a potential issue increasing the
importance of efficient airtightness at the design
stage.
Identifying thermal bridging
Part L of the Building Regulations has recently
been updated, requiring a reduction of 31% fewer
carbon emissions for dwellings, and 27% for
advice on thermal bridging calculations – to
contractors and designers. This service helps the
client to identify and specify the right material
and required thickness for maximum efficiency.
The calculations demonstrate the effect of
thermal bridging before and after applying the
chosen solution.
Continued on page 66
64 TC NOVEMBER 2022