Thermal bridging to impact Total R-Values from May 1st
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The transition period for the requirements of the National Construction Code (NCC) introduced in May 2019 will be ending on May 1st 2020. NCC 2019 introduced significant changes to the provisions outlined in Section J of Volume 1, which sets out the requirements for energy efficiency of buildings. For the first time in the Australian construction industry’s history, the effects of thermal bridging will have to be fully accounted for in thermal computations. NCC 2019 saw an introduction of a direct reference to NZS 4214: 2006, a method used in the New Zealand Building Code, to determine the total thermal resistance of building elements. The introduction of a direct reference of this method in Australia means that thermal bridging between building elements will now have to be accounted in thermal computations for most building classifications, directly impacting the Total R-Value of the built system.                                     

“We have been providing technical advice and computations to our customers in New Zealand for several years now taking into account the effects of thermal bridging, so this will not be a massive change for us, while maintaining our high level of service to our customers,” said Killian Smith, Kingspan Insulation’s Technical Services Manager.                                                                                                            

Thermal bridging occurs when there is a break in the insulation, less insulation, or the insulation is interrupted by an element with a higher thermal conductivity. Thermal bridges are paths of least resistance for heat to escape or enter the building envelope. The introduction of thermal bridging in thermal computation process will have a major impact on the predominant way of building in Australia, such as using batts and stud frames.                                                           

“The amended way of calculating thermal performance will significantly impact the traditional wall systems made up of batt insulation bridged by metal or timber studs. These systems will see a dramatic fall in Total R-Value,” added Smith.           

Traditionally system R-Value would have been calculated by adding up the R-Values of all the materials making up the system. The direct reference to NZS 4214:2006 mandates instead that Isothermal Planes Pathways need to be calculated, taking into account the heat that leaks through the repeating thermal bridges in the construction. These “leaks” will lead to an overall decreased thermal performance of the whole system. To make up for that, designers may need to design thicker walls, leading to less design freedom, or opt for continuous insulation solutions that achieve higher R-Values. “Achieving the target R-Values for walls will be challenging using just the traditional insulation systems. I expect we will see more architects and designers using continuous insulation on its own or as a part of the framed system, to raise the total R-Value,” concluded Smith.