Fixing and buying guide

What this product is and who needs it

The BDX Insulation Collar is a flashing collar that sits between your VELUX roof window or Sun Tunnel system and the roof structure. It prevents water ingress, maintains the integrity of your building envelope, and provides a neat, visually consistent finish at roof level. This product is essential for roofers, builders, and experienced DIY installers carrying out new build work or refurbishment projects where VELUX roof windows or Sun Tunnels are being fitted.

Compatibility and sizing

This collar is engineered specifically for VELUX roof window and Sun Tunnel ranges. Before ordering, confirm that your chosen VELUX system is compatible with the BDX collar type. The collar dimensions are 940 x 1600mm, which accommodates standard roof window opening sizes. Check your roof window specification sheet or installation manual to verify compatibility, as different VELUX models may require different collar types.

• Compatible with VELUX roof window systems
• Compatible with VELUX Sun Tunnel systems
• Dimensions: 940 x 1600mm per collar
• Pack contains 10 units

Pack contents and quantity planning

Each pack supplies 10 insulation collars. If you are installing a single roof window, one collar will suffice; however, this bulk pack is ideal for multiple installations, new build projects with several windows, or where you need spares. Calculate your requirement based on the number of VELUX windows or Sun Tunnels being installed, then order accordingly.

• 10 collars per pack
• One collar required per roof window or Sun Tunnel installation
• Suitable for new build and refurbishment projects

Pre-installation checks and preparation

Before fitting, inspect the roof opening to ensure it is square, level, and matches the collar dimensions. Check that the roof structure is sound and free from damage. Verify that your VELUX window or Sun Tunnel system is compatible with the BDX collar by consulting the product documentation. Ensure you have the correct flashing materials and sealants recommended by VELUX for your roof covering type (slate, tile, felt, etc.). The collar is engineered for UK roof conditions, but proper installation is essential to achieve a weather-tight seal and long-term durability.

• Confirm VELUX system compatibility before installation
• Inspect roof opening for square and level fit
• Check roof structure is sound and undamaged
• Prepare appropriate flashing materials and sealants for your roof covering type
• Follow VELUX installation guidance for weather-tight sealing