Fixing and buying guide

What this product is and who needs it

This insulation collar is a fiberglass thermal seal that sits around the frame of a VELUX roof window. It is essential for anyone installing or renovating a loft window in a UK home, particularly where energy efficiency and draught prevention are priorities. The collar works by closing the gap between the window frame and the surrounding loft insulation, eliminating cold spots and reducing heat loss that would otherwise occur through thermal bridging.

Sizing and compatibility

This collar measures 78x98cm and is designed for standard UK loft window openings up to 98cm in width. It is specifically engineered for VELUX roof windows and carries the BDX MK04 2000 specification. Before ordering, measure your loft opening to confirm it falls within this size range. If your opening is significantly larger or smaller, you may need a different collar size.

• Dimensions: 78x98cm
• Suitable for standard UK loft installations
• Compatible with VELUX roof window systems
• Check your window opening width does not exceed 98cm

Installation and preparation

The collar is straightforward to fit and can be installed during initial window fitting or as part of a retrofit upgrade. Position it around the window frame perimeter before or during insulation work, ensuring it sits flush against both the frame and the surrounding insulation. This creates the tight seal needed to eliminate draughts and cold air paths. Installation is typically completed as part of standard window fitting procedures and requires no specialist tools.

• Install during window fitting or retrofit work
• Position around the entire frame perimeter
• Ensure flush contact with frame and insulation
• No specialist tools required

Pre-installation checks

Before fitting, confirm that your loft opening dimensions match the 78x98cm specification and that you are installing a VELUX roof window system. Check that the area around the window frame is clear of debris and that your loft insulation is ready to be fitted around the collar. Ensure the window frame itself is level and properly positioned in the roof opening, as the collar will only seal effectively if the frame is correctly installed.

• Verify opening dimensions suit 78x98cm collar
• Confirm VELUX window compatibility
• Clear debris from around the window frame
• Check window frame is level and properly positioned