Insulation Thermal Effectiveness

Wall Insulation Thermal Effectiveness (NZBC H1, AS/NZS4859.1:2002)

Insulation thermal effectiveness

Wall insulation thermal effectiveness is achieved by filling all except the narrowest wall cavities (eg: frame corners), without joints, gaps or edge crushing common with batting installation. The high-density dry fill process eliminates settlement and curing shrinkage away from framing timber, common with liquid foam materials. Total thermal effectiveness is guaranteed with installation of design thickness and weight.

When exterior wall insulation is added to an existing or new build wall construction, compliance with NZ Building Code (NZBC) clauses H1.3.1 (a) and H1.3.2 is achieved via H1/AS1, clauses 2.1, 2.2 and 2.3. The minimum Total R-values R1.9 / R2.0 (depending on zone) stipulated in Tables 2 of NZS4218 and NZS 4243, are exceeded respectively with all wall cavities >75mm. Alternatively, Licensed installers can complete a design on an individual building in accordance with NZS4218 calculation method, using the table figures.

Table 1 – Thermal Resistance – CosyWall Cavity Walls.

For a Total R-Value of:Material

R-Value :


Kg/m2 wall ex openings

Minimum Thickness (mm)
2.7 (2)3.12.5100
3.5 (3)4.33.5140


(1) Weatherboard >1950 with nogs. Deduct R0.2 if Sheet cladding

(2) Weatherboard <1950 510c/c, no horizontal nogs, no wrap

(3) Sealed Brick Veneer 50mm gap , no wrap (1)&(3) Total R-values assume no wraps18% thermal bridging as per H1/AS1 & may alter in walls with more or less framing timber.


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