R1300 Flat Concrete Roof with Suspended Ceiling Plenum Return (ventilated)

Structure

ICANZ system reference for this roof is R1300 - Foil faced blanket underside of concrete roof.Foil facing downwards.

Installation

• R1330 allow for R2.5 batt positioned on suspended ceiling grid.
• Fix reflective polystyrene 30mm to underside of concrete. R2.5 batts positioned on suspended ceiling grid.
• In all cases air space below foil assumed to be ventilated acting as a return plenum, 100mm - 600mm air space. Reflective bright side of foil faces downwards, i.e. Ceiling void used as a return air plenum.

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.

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.