Does anyone have any advice with regard to ducting the MVHR intake & extracts through a TF with 300mm cellulose? What did you do with the external membrane? My ducting will go through the wall into a small void in the roof overhang & then a bend in the duct to attach to external grills in the cedar cladding cloaking the underside of the overhang.. Internal wall is airtight OSB (the green stuff). Thanks. M