Fixing and buying guide
VELUX Insulation Collar 78x140cm BDX MK08 2011
What this product is and who needs it
This insulation collar is a fibreboard sealing component that bridges the gap between your insulation layer and timber structural members in the loft. It is essential for builders, roofers, and serious DIY installers carrying out loft insulation work who need to eliminate thermal bridging and air leakage around roof trusses and timber frames. The collar prevents warm air from escaping through gaps that would otherwise compromise the overall insulation performance of your loft space.
- Fibreboard construction to BDX 2011 grade for durability
- Sized at 78 x 140cm for standard loft installations
- Suitable for both new build and retrofit applications
- Designed to work with roof trusses and timber frame systems
Compatibility and sizing
The 78 x 140cm dimensions are designed for standard loft construction where insulation needs to be sealed around typical roof truss spacing and timber frame widths. Before ordering, measure the gaps between your insulation and structural timber elements to confirm this size will cover your application. The collar is compatible with timber frame and roof truss systems in conventional loft construction. If your structural spacing or timber dimensions differ significantly from standard specifications, you may need to assess whether this size is appropriate for your project.
- Dimensions: 78 x 140cm
- Designed for standard roof truss and timber frame spacing
- Measure your gaps before purchase to confirm fit
- Suitable for both pitched roof and flat roof loft applications
Installation and preparation
Position the insulation collar around the timber structural member so it sits between the insulation layer and the timber frame or truss. The fibreboard should create a continuous seal, eliminating gaps where heat loss could occur. Ensure the insulation is properly compressed and in contact with the collar to maintain thermal performance. The collar should be fitted before or during insulation installation to prevent gaps from forming. Check that all edges are in firm contact with both the insulation and the timber to create an effective thermal barrier.
- Install around timber frames and roof trusses before or during insulation placement
- Ensure full contact between collar, insulation, and timber
- Compress insulation firmly against the collar to eliminate voids
- Check for gaps around all edges of the installed collar
Pre-installation checks
Before fitting, inspect the collar for any damage to the fibreboard and confirm the dimensions match your structural spacing. Verify that your timber frame or roof truss dimensions are compatible with the 78 x 140cm size. Check that your insulation material will sit properly against the collar without leaving voids. Ensure the loft space is adequately ventilated according to building regulations, as the collar seals gaps but does not replace required ventilation pathways. Review your project specifications to confirm this BDX 2011 grade product meets your thermal and durability requirements.
- Inspect fibreboard for damage before installation
- Confirm timber spacing matches the 78 x 140cm dimensions
- Verify insulation material compatibility
- Check loft ventilation requirements are maintained
- Confirm BDX 2011 grade meets your project specification