I wonder, has anyone here used the MBC open panel 140mm wall system (as compared with the 300mm twin stud)?   I know quite a few on here have used the MBC 300mm passive-house twin-stud wall system but for a range of reasons* I am thinking of specifying the open panel 140mm wall from MBC instead with external-wall upgrade to U-Value 0.11W/m2K.   I have some questions about the airtightness with the open panel system using the Protect VC Foil Ultra airtightness layer.