Fixing and buying guide

What this product is and who needs it

The vapour barrier collar is a specialist component that sits between your VELUX roof window or Sun Tunnel and the roof structure. It manages moisture vapour from inside the building, preventing condensation and damp problems that can occur at the roof penetration. This product is essential for anyone installing a VELUX roof window or Sun Tunnel system, whether you are a builder, surveyor, or experienced DIY installer carrying out a refurbishment or new build project.

Compatibility and sizing

This collar is designed specifically for VELUX roof windows and Sun Tunnel systems and carries the product code MK04 0000. The 780×980mm size is the standard dimension for MK04 compatible installations. Before ordering, confirm that your VELUX window or Sun Tunnel model requires the MK04 collar specification. Check your VELUX documentation or product code to ensure compatibility, as different window sizes and types may require different collar variants.

• Product code: MK04 0000
• Size: 780×980mm
• Compatible with VELUX roof windows and Sun Tunnels only
• Verify your window model number before purchase

Installation and pre-install checks

The vapour barrier collar must be installed as part of the complete VELUX flashing system to ensure a weather-tight seal. It works in conjunction with the external flashing, insulation collar, and internal trim components. Before installation, inspect the collar for any damage and ensure your roof opening is cut to the correct size according to VELUX specifications. The collar should be positioned on the warm (internal) side of the insulation layer to manage vapour effectively. Follow the detailed installation instructions provided with your VELUX window kit, as correct positioning and sealing are critical to performance.

• Install as part of the complete VELUX flashing system
• Position on the warm (internal) side of insulation
• Ensure roof opening matches VELUX specifications
• Seal all joints and edges according to manufacturer guidance
• Use appropriate sealants and tapes recommended by VELUX

Pack contents and storage

Each pack contains one vapour barrier collar sized 780×980mm. Store the collar in dry conditions before installation to prevent damage. Keep it flat or in its original packaging to avoid warping. Do not expose to direct sunlight or extreme temperatures during storage, as this may affect the material properties.