Fixing and buying guide
VELUX Vapour Barrier 78x140cm BBX MK08 0000
What this product is for
This vapour barrier is designed specifically for VELUX roof window installations. It manages moisture migration by preventing water vapour from entering the insulation layer, which would otherwise cause condensation, dampness, and thermal performance loss. The barrier sits between your room and the insulation, creating a protective layer that extends insulation life and helps maintain a dry, healthy interior.
- Prevents moisture vapour penetrating insulation layers
- Reduces condensation risk around roof window openings
- Maintains insulation thermal performance and longevity
- Protects interior environment from damp-related issues
Sizing and compatibility
This barrier measures 78 x 140cm and is sized to fit standard VELUX roof window openings at size MK08. Before ordering, confirm your roof window model and opening dimensions match this specification. The barrier is compatible with VELUX roof window systems; check your window documentation or product code to ensure compatibility.
- Dimensions: 78 x 140cm
- Designed for VELUX MK08 roof window size
- Verify your roof window model before purchase
- Not suitable for non-VELUX installations or different window sizes
Installation position and preparation
The vapour barrier must be installed on the warm side of the insulation layer, which means on the room-facing side of your roof window opening. This positioning is critical for the barrier to function correctly. Before installation, ensure the opening is clean and dry, and that all insulation is properly fitted. The barrier should be installed before any internal finishes such as plasterboard or cladding are added.
- Install on the warm side of insulation (room-facing side)
- Position before internal finishes are applied
- Ensure opening is clean and dry before fitting
- Check insulation is properly in place and secure
What you need to know before buying
This is a single vapour barrier membrane for one roof window opening. If you are installing multiple VELUX windows, you will need one barrier per window. The barrier works as part of a complete roof window installation system; ensure you have all other necessary components such as flashing kits and insulation before you begin work. For best results, follow VELUX installation guidance specific to your window model.
- One barrier per roof window opening
- Part of a complete VELUX installation system
- Order additional barriers if installing multiple windows
- Refer to VELUX installation instructions for your specific window model