Metal Roof with Ceiling below Rafters

ICANZ System Reference R0400

Structure

Metal cathedral roof at 22.5o pitch with foil faced blanket product over 40mm battens with 200mm deep rafters ceiling insulation, battens with 10mm plasterboard fixed below.

Insulation Installation

Reflective insulation shall be draped over or under battens to create a 40mm air space. All joins should be lapped 150mm in accordance with AS/NZS 4200.2. To maintain effectiveness as insulation any tears or gaps shall be repaired with a suitable reflective foil tape. Where insulation batts (eg R3.0) are incorporated in the structure a 25mm reflective airspace is maintained between the lower side of the foil and the batts.

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.