Definition of cold roof in the UK
In order to put the cold ventilated roof system into context, we will refer to it as a roof where there is a continuous air space of at least 50mm between the substrate supporting the zinc and the insulation. This air space must be a vented space with openings generally at the eaves and the ridge.
Hybrid roofs are not recommended by VMZINC and can result in the whole roof including the zinc failing.
Cold Roof: Air inlets and outlets are generally linear (at least 10mm open) but can be individual. The ventilation must correspondto BS: S250: 2002.
Fundamental elements of the system:
- VMZINC PlUS must be used on plywood whereas VMZINC is acceptable on open-gap softwood boards.
- VMZINC Membrane can be used to protect the insulation.
- The substrate must be continuous and even, and the correct fixing clips must be used.
Linear air vents must be at least 10mm open and are commonly protected by insect mesh. It is always good practice to include a vapour control layer in the build up and this should be installed on the warm side of the insulation. The system is covered by the Code of Practice 143-5: 1964.
