Flat Metal Roof Suspended Ceiling with Plenum Return
ICANZ System Reference R1100
Structure
Metal roof at 0 to 5o pitch, with foil faced blanket over safety mesh. 10mm plasterboard ceiling fixed to the suspended ceiling grid to form a 200-600mm ventilated air space i.e. Ceiling void used as a return air plenum.
Tight safety mesh denotes no airspace between reflective insulation and flat metal roof. Hence no contribution from an airspace.
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.
G. Due to the ceiling void being used as a return plenum, elements including the ceiling void air space and below cannot be considered in the calculations. These elements have nil affect on maintaining temperature leakage as the conditioned room temperature is assumed to be the same within the ceiling void. Any insulation sitting on the ceiling only has insulation benefit when the HVAC system is off.
