Fixing and buying guide

Who this product is for

This insulation collar is for builders, roofers, and serious DIY installers undertaking new build or refurbishment projects that include VELUX roof windows or Sun Tunnel systems. It is essential if you want a professional, weather-tight finish that meets building standards and maintains the visual integrity of the roof line.

Compatibility and sizing

The BDX MK08 2000 collar is engineered to work with VELUX roof window and Sun Tunnel ranges. Before ordering, confirm that your VELUX product is compatible with the MK08 size designation. The collar dimensions are 780 x 1400mm, which corresponds to the MK08 window size. Check your roof window specification or contact VELUX technical support if you are unsure of the correct collar size for your installation.

• Compatible with VELUX roof windows and Sun Tunnel systems
• Size designation MK08 – verify compatibility with your specific VELUX product
• Dimensions 780 x 1400mm

What is included and pre-installation checks

The BDX MK08 2000 is supplied as a complete insulation collar flashing unit ready for installation. Before fitting, ensure the roof opening is cut to the correct dimensions and that the surrounding roof structure is sound and level. Check that all VELUX window components are on site and that you have the correct collar size for your roof window model. Inspect the collar for any damage in transit.

• Complete flashing collar unit supplied
• Verify roof opening dimensions match the 780 x 1400mm collar size
• Confirm VELUX window and collar compatibility before installation
• Check roof structure is level and sound around the opening

Installation and performance

The insulation collar creates a weather-tight seal between the roof window frame and the roof structure, preventing water ingress and heat loss. It supports a neat, professional finish that is visually consistent with the roof line. The collar is engineered for reliable performance in UK roof conditions, including exposure to rain, wind, and temperature variation. Follow VELUX installation guidance and ensure the collar is fully secured and sealed according to the manufacturer's instructions for optimal long-term performance.