Thermal Bridging: A Challenge for the Wall Tie Industry
Wall Ties are an essential element in the strength and stability of a cavity wall, but by crossing the cavity they act as a thermal bridge between the internal and external leaves. Generally speaking, the wider the insulated cavity, the more substantial the Wall Tie needs to be and the greater the effect the tie will then have on the U-value of the wall.
The challenge for the Wall Tie industry, set by the Government’s ambitious energy efficiency targets, is to reduce the thermal conductivity of its products whilst continuing to meet the structural performance requirements of wide cavity construction.
Ancon Building Products has met this challenge by launching a new range of Low Thermal Conductivity Wall Ties; ties which minimise heat loss through thermal bridging, thereby improving the energy efficiency of a wall. These products can actually be used to reduce insulation thickness and therefore provide savings on construction materials and wall footprint.
This new range of Ancon Wall Ties suits cavities from 50mm to 300mm, essentially future-proofing traditional masonry cavity wall construction with which all clients, contractors and designers are familiar.
In addition to a number of high tensile stainless steel wire Wall Ties, this range includes the new Ancon TeploTie which is manufactured from pultruded basalt fibres set in an epoxy resin.
The TeploTie has a BBA approval and is available exclusively from Ancon Building Products. It has a thermal conductivity of just 0.7W/mK, making it the most thermally efficient Wall Tie on the market. All fixings with a conductivity rating of under 1.0W/mk are excluded from U-value calculations to EN ISO 6946.
TeploTie has already been used on the UKs first zero-carbon retrofit project to achieve level 6 of the Code for Sustainable Homes and the UK’s first certified Passivhaus to be built using masonry cavity walls.
When calculating a U-value it is important to use the actual cross-sectional area of a Wall Tie and the thermal conductivity of the material from which it is manufactured, rather than allowing a calculation program to apply default values. This can make a considerable difference to the result; a default value will over-estimate the thermal bridging effect of an Ancon Wall Tie and designers may increase insulation width and wall footprint unnecessarily.