58 BUILDING FABRIC


failure to meet surface temperature performance factor fsi fi gures.


THERMAL PERFORMANCE & STRUCTURAL INTEGRITY


any designers are still not fully aware of ust how signifi cantly thermal bridges can affect insulation performance – and that the most effective way to minimise thermal bridging at cantilever balcony detailing is to incorporate a load-bearing structural thermal break. This is a highly effi cient balcony connector that minimises the  ow of thermal energy between the interior and exterior of a building, providing both structural integrity and thermally isolating the balcony. A structural thermal break has a very specifi c purpose and for longterm effectiveness requires certain physical characteristics – optimum thermal insulation thickness for the application in question, load-bearing components and a combination of reinforced and stainless steel. Solutions are available for applications as diverse as concrete-to- concrete, concrete-to-steel, steel-to-steel, renovations, even Passivhaus.


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CONDENSATION & MOULD GROWTH One consequence of thermal bridging is that cold surfaces can form condensation, resulting in both visual deterioration and structural damage. However, an even bigger concern is mould growth. To identify areas where there is a risk of condensation and therefore mould growth, a ‘surface temperature factor’ (fRsi) should be used.


t allows surveys under any thermal conditions and compares the temperature drop across the building fabric with the total temperature drop between the inside and outside air. The recommended fsi value for offi ces and retail premises is equal to or greater than 0.5; and to ensure higher standards for occupants in residential buildings, equal to or greater than 0.75.


RESPONSIBLE DESIGN FOR THE FUTURE The UK has set in law a target to bring all its greenhouse gas emissions to net zero by . As part of that ourney, there is a commitment to introducing the Future Homes Standard in 2025 – and the higher performance targets of 2


emissions


being reduced by  for dwellings and  for other buildings  is an interim step towards that standard. The thermal performance of the building envelope is therefore of increasing importance – and critical to this is the avoidance of thermal bridging.


THIRTEEN PRODUCT VARIANTS FOR HENDON


One ongoing current project with a demanding variety of cantilever balconies – and therefore thermal bridging challenges – is Hendon Waterside in North West London. Situated alongside the Brent Reservoir, the scheme involves a six-phase regeneration of a 1960s housing estate. The masterplan will deliver around 2100 new homes being constructed in twentythree blocks. The construction of the many balconies involved vary in their design demands and to ensure the risk of thermal bridging is minimised, Schöck has supplied over thirteen different structural thermal break variants.


Simon Hill is product and marketing manager at Schöck


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