Standard revised for thermal insulation


Standards New Zealand has published a revised Standard specifying Thermal insulation – Housing and small buildings, NZS 4218:2009, which supersedes NZS 4218:2004.
NZS 4218 specifies thermal insulation requirements for housing and small buildings for users of the Standard — architects, designers, building consent authorities and window and glass companies.

“The Standard is also useful for the building industry, including window and glass manufacturers, insulation manufacturers, and manufacturers and suppliers of building products so they can provide advice and stock appropriate products,” BRANZ committee chairman Michael Camilleri says.
“Ambiguities in the previous version of NZS 4218 have been resolved, and there is additional guidance with more worked examples.”

The revised version of NZS 4218:
• includes modified R-value tables and brings the Standard into line with these increased performance requirements. The construction R-values in this Standard result in a low life-cycle cost, based on current knowledge of insulation costs, energy costs, and heating behaviour,
• clarifies the three different ways of working out R-values (schedule method, calculation method and modelling method), and ensures consistency between the different methods, and
• includes clearer definitions.

Some of the most significant changes are:
• adjusted R-values to reflect improved energy efficiency,
• changes to the calculation method to ensure adequate thermal performance is not compromised by large glazing areas,

• a revised modelling method to take account of recent research, and to make it easier to use with recent computer modelling packages,
• new requirements for high thermal mass construction to ensure the thermal mass is adequate and effective,

• a revised appendix (now Appendix C) on windows and glazing,
• a new informative Appendix D provides guidance on alterations and how they can achieve higher thermal resistance,
• more worked examples in informative Appendix F,

• the new term construction R-values has been introduced to distinguish the performance values in this Standard from insulation material R-values.

“There is more clarity on the use of doors, skylights, decorative glazing and louvres, Glass Association of New Zealand (GANZ) Technical Advisor and committee member Allan Sage says.

“Appendix D – Windows and Glazing has been revised, offering more glazing options and guidance for users wanting to calculate other glass and frame combinations.
“A new term (RWindow) has been introduced to overcome confusion over the R-value for glass only (RCOG) and the total window R-values (RWindow).”

‘The major change for the window industry is the reduction of the limit on glazing area from 50% to 40% for the calculation method. The modelling method must be used for a glazing area over 40% of the total wall area.
“This will see more modelling of complex houses in the future, which GANZ believes is a positive move to stop over-heating and under-heating issues with modern house design.”