R0800 Flat Metal Roof with Plasterboard Ceiling (exposed rafters)

Structure

ICANZ system reference for this roof is R0800 - Flat metal roof of between 0 and 5 degrees of pitch with R1.8 foil faced blanket product draped over minimum 110mm high batten which is located over ceiling lining and roof rafter. Foil facing downwards to minimum 15mm air space, 10mm plasterboard ceiling fixed between batten and exposed rafter.

Installation

• Option 1: Double side antiglare foil positioned over minimum 110mm batten. 70mm air space below double sided antiglare foil replaced with 20mm air space and R1.5 - 50mm bulk insulation. Bulk insulation laid over ceiling lining.
• Option 2: Double sided antiglare foil draped over minimum 110mm batten providing 40mm air space with antiglare side of foil facing metal roof. Reflective EPS board positioned at mid height of remaining 70mm air space providing 20mm air space above and below reflective EPS board.
• Option 3: Polyweave or double sided antiglare or bubble foil draped over 90mm batten providing 40mm air space between metal roofing and foil. 50mm air space between foil and plaster ceiling.

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

A. Calculations assumptions in accordance with AS/NZS 4859.1:2002.  Amendment 1. 2006. Amendment 1. 2006 on the path of the insulation, as required by the BCA Vol 1. Part J and Vol 2. Section 3.12.

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.