Cold Roof Vapour Control Layer

We would recommend either a fully warm roof with insulation on top of the roof deck or a cold roof with a minimum 50mm well ventilated cavity between the roof deck and the top of the insulation.

Cold roof vapour control layer.

It s the first line of defence against high vapour pressure air entering the roof structure and causing interstitial condensation. Vapour control layers should be provided to warm roofs and. Bs6229 2003 gives advice on vapour control layers in flat roofs and the control of condensation within the building generally. A vapour control layer or vcl on a warm flat roof sits between the roof decking and the insulation.

The roof is an unventilated warm roof design finished with a single ply membrane. It has transpired that there is no vapour control layer fitted. A vapour control layer helps you shield your building from the consequences of condensation condensation is generated when warm moist air rises and condenses into a liquid on contact with the cooler areas above the insulation. Include at least one layer of bitumen roofing membrane s2p3 below the insulation fully bonded or mechanically fixed to the structural deck as appropriate or a suitable self adhesive or torch on membrane.

Where the ceiling below a cold pitched roof includes a vapour control layer the design should ensure adequate ventilation is provided to the habitable areas to prevent condensation problems in the home. An inverted roof construction sees the principal thermal insulation layer located above the roof structure and also above the waterproofing this method results in the waterproofing the structural deck and the support structure all being at a temperature similar to that of the interior of the building. Meets building requirements non ventilated pitched roof systems that use tyvek as roofing underlay satisfy the requirement of approved document c2. Because the waterproofing layer constitutes a vapour control layer on the cold side of the insulation there is a high risk of harmful interstitial and surface condensation on the underside of the deck or the upper surface of the.

To solve this we recommend installing an air vapour control layer avcl such as duponttm airguard control beneath the vapour open quilt insulation. This type of roof has normally been used over small extensions to dwellings using timber joists and plywood deck. The architect plans stated requirement for a vapour control layer below the insulation or a 3 in 1 insulation board including vapour control layer and an additional foil backed plasterboard. The notion behind a vapour control layer is to install it on the room.

Be it a cold or warm roof construction the primary function of a vcl is to keep warm moist air from inside the building inside the building.