Metal Roof with Cathedral Ceiling above Rafters

ICANZ System Reference R0600

Structure

Metal cathedral roof at 22.5o pitch with foil draped over 90mm batten providing 40mm air space with antiglare side of foil facing metal roof. 50mm air space between foil and 10mm plasterboard ceiling fixed between batten and exposed rafter.

Insulation Installation

Option 1: R1.8 roofing blanket adhered to RFL vapour barrier foil product draped over 110mm high battens which are located over ceiling lining and roof rafter. Foil facing downwards to minimum 15mm air space.

Option 2: Double sided antiglare foil over minimum 110mm batten. Remaining 70mm air space below double sided antiglare foil replaced with 20mm air space and R1.5 - 50mm, bulk insulation. Bulk insulation positioned over 10mm plasterboard ceiling fixed between batten and exposed roof rafter.

Option 3: Double sided antiglare foil over minimum 110mm batten. Reflective EPS board positioned at mid height of remaining 70mm air space providing 20mm airspace above and below reflective EPS board.

Option 4: Polyweave or double sided antiglare foil draped over 90mm batten.

NOTE: Total R-Values can be increased by substituting bulk insulation products of higher Material R-Value.

A. In accordance with AS/NZS 4859.1:2002.  Amendment 1. 2006.

B. Temperatures and parameters are based on Australian climate assumptions. Air temperature difference 12oC (36oC less 24oC) for summer conditions and 6oC difference (18oC less 12oC) for winter.

C. Thermal resistance of air films and attic spaces based on values obtained from Section K5 and K6 of AS 4859.1:2006.

D. Building material elements based on 2000 AIRAH Handbook and attic thermal value based on AS4859.1 app K6 table K2.

E. Where reflective insulation is installed, a simple addition of R-values is not possible. Care must be taken to ensure the performance of reflective air spaces is not “double-counted”.

F. The emittance of the reflective surfaces are dependent on tested values and the conditions of the installation, as specified by AS/NZS 4859.1. Amendment 1. 2006.