DWF Fire-Rated Knee Wall Access DoorDWF Fire Rated Knee Wall Access Door The Fakro DWF Fire Rated Knee Wall Access Door provides safe, reliable access to non habitable spaces behind knee walls while maintaining fire safety standards. Designed for residential use, this door features a 2 thick sash with fire resistant insulation and a finished white surface on both sides. With an R value of 8. 9, the DWF door offers excellent thermal insulation, reducing heat transfer throughout the year.