Premade lengths of ducting made especially to go out through soffit boards along with prewrapped insulation. This ducting goes from 100mm solid ducting to solid and flexible 204 x 60 ducting which is the equivalent of 125mm round ducting. This allows the installer to go between the wall plate and roofing felt while reducing the resistance going through the soffit board. Many installers use just 100mm flexible ducting and squash it down in size to go between the wall plate and the roofing felt. This greatly increases the resistance of the ducting and hence the flow rate of the fan. The soffit vent comes with 750mm of solid ducting and 1.2 meters of duct wrap insulation. Additional ducting and duct wrap insulation can be purchased on this site.
