Reply To: Underfloor insulation mandatory?

[Ian McChesney]

Hi Phil
My understanding is that the building will need to comply with H1. But H1 contains flexible options. The normally prescribed R1.3 for floors that you are probably thinking about is the minimum value contained in various ‘schedule methods’ for meeting the code. Schedule methods are like off-the-shelf prescribed solutions. The alternative is the ‘calculation method’. The latest H1 compliance document states:

“… “calculation method” of NZS 4218
compares the proposed building with the “reference
building” which is insulated in accordance with
Tables 1, 2 and 4 (as modified by Paragraphs 2.1.3
and 2.1.4). This method permits roof, wall, floor and
glazing insulation combinations which differ from
these Tables, but the building must still perform at
least as well as the “reference building”.

Note that the tables referred to above are the schedule methods. Therefore my understanding is that the Calculation Method of H1 would allow for low floor R values, so long as other elements of the house compensate with higher R values.

I suggest you confirm this understanding with someone regularly dealing with new houses.

cheers
Ian

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