Building Construction Handbook, Eighth Edition

Conservation of Energy ~ this can be achieved in two ways:

1. Cold Deck † insulation is placed on the ceiling lining, between

joists. See page 448 for details. A metallized polyester lined

plasterboard ceiling functions as a vapour control layer, with

a minimum 50 mm air circulation space between insulation and

decking. The air space corresponds with eaves vents and both

provisions will prevent moisture build-up, condensation and

possible decay of timber.

2. (a) Warm Deck † rigid* insulation is placed below the
   waterproof covering and above the roof decking. The insulation
   must be sufficient to maintain the vapour control layer and roof
   members at a temperature above dewpoint, as this type of roof
   does not require ventilation.

(b) Inverted Warm Deck † rigid* insulation is positioned above the

waterproof covering. The insulation must be unaffected by

water and capable of receiving a stone dressing or ceramic

pavings.

* Resin bonded mineral fibre roof boards, expanded polystyrene or

polyurethane slabs.

Typical Warm Deck Details ~

Timber Flat Roofs---Thermal Insulation