Home Forums General Discussion Underfloor insulation mandatory? Reply To: Underfloor insulation mandatory?

Gleb Speranski

Hi Phil,

I agree with all the earlier comments but would like to add something for clarity.
Unfortunately NZS 4218 is still sited in H1 in its old, 2004 version. The standard treats draped foil as a ‘deem to comply’ insulation option for suspended timber floor. That means that even though BRANZ already established that the installed performance of a floor with draped pliable membrane is a fat zero, new builds still comply with the schedule method with foil. That is how deficient the whole ‘performance based’ approach of the Code is.
It should be noted that the more recent version of 4218 published in 2009 (?) is a lot stricter and introduced some good changes like a 6% limit, by surface area, on doors (including garage doors).
However, the political climate has already changed at the time the 2009 version was published and therefore it still remains a voluntary standard.
Back to your question- no, insulation is not mandatory: a house can be constructed in such a way that compliance with H1 is achieved by other means- solid walls, smaller double glazed windows, etc.