Fixing and buying guide

What this product is and who needs it

The insulation collar is a flashing component that sits between your VELUX roof window or Sun Tunnel and the roof deck. It is designed for builders, roofers, and serious DIY installers who are fitting VELUX systems into pitched roofs. Whether you are installing a new window in a loft conversion or replacing an existing unit during refurbishment, this collar ensures a professional, weather-tight finish that protects the building fabric from water penetration and heat loss.

Compatibility and sizing

This collar is sized 550 x 780mm and is compatible with standard VELUX roof window and Sun Tunnel ranges. Before ordering, confirm that your VELUX window model matches this collar size. Check your window documentation or the product code on your existing unit. The BDX CK02 2000 code identifies this specific collar type; using the correct size is critical for a weather-tight seal.

• Dimensions: 550 x 780mm
• Compatible with VELUX roof windows and Sun Tunnel systems
• Product code: BDX CK02 2000
• Verify your window model before purchase

Pre-installation checks and preparation

Before fitting, inspect the roof opening to ensure it is square and the correct size for this collar. Check that the roof structure around the opening is sound, with no rot or damage to the timber. Ensure you have the correct flashing materials for your roof covering type (slate, tile, or sheet material). The collar must sit flush against the roof deck with no gaps. Have all fixings and sealants ready before starting work, and plan your installation to avoid weather exposure.

• Verify roof opening dimensions match the collar size
• Inspect roof structure for damage or rot
• Confirm compatibility with your roof covering material
• Gather fixings and sealants appropriate for your roof type
• Plan installation to minimise weather exposure

Installation and performance

The collar is engineered to perform reliably in typical UK roof conditions and contributes to an integrated daylight and ventilation strategy for your property. Proper installation is essential: the collar must be secured firmly to the roof deck and sealed against water ingress using appropriate roof sealant. The flashing should be integrated with your roof covering so that water runs away cleanly. This is a critical component of the window installation system and should be fitted according to VELUX installation guidance and building regulations requirements.