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Andrea Blackmore
ER53 Thermal Bridging In External Timber-Framed Walls

ER53 Thermal Bridging In External Timber-Framed Walls by Verney Ryan, Guy Penny, Jane Cuming, Ian Mayes, Graeme Baker, ER53_Thermal_Bridging_in_External_Timber-Framed_Walls.pdf (3.4 MiB) – This report shares the results and findings of a project to investigate the extent of thermal bridging
in external timber-framed walls of new builds. The research methodology has evolved as the
team gathered information, and is detailed. The Wall Project took a case study approach to
investigate the percentage of framing in 47 newly constructed dwellings from Auckland,
Christchurch, Wellington and Hamilton. The results show that the average percentage of timber
framing compared to the area of the wall is above 34%. This is much higher than the 14 – 18%
framing content generally assumed by both regulators and the industry. The results strongly
indicate that the content of timber framing in external walls in residential new builds is at such
high levels that the increased thermal bridging compromises the performance of walls and may
mean that designed R-values are not being achieved. There is evidence that increasing framing
content is being driven by the requirements of various regulations, mostly in relation to structure
and weathertightness. In addition, there is also evidence that the definitions used in current
construction R-value calculation methods for achieving energy efficiency and internal moisture,
ignore significant areas of thermal bridging in wall framing. The report includes the results of
measuring framing in the 47 individual case study dwellings, and what the research team have
learned from both interviews with industry members, as well as through measurement and
analysis of the case study houses. In concluding, the report highlights opportunities for further
suggested research activity that could assist in improving the thermal performance of walls in
New Zealand.