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Hello All, I'm trying to work out the U value requirement of a pitched roof. Its an extension roof and Building Regs require a .16 U value at the ceiling level.
This is the roof makeup thus far
Clay Tiles 20mm
Breather membrane (0.1 mm)
Air layer/battens 30mm
Rafters 200 mm
To get to a .16 the U calculator at Rockwool for example has the following after the tile/membrane
HARDROCK® Multi-Fix (DD) (50 mm)
FLEXI® (200 mm)
Unventilated air layer (10 mm)
Polyethylene/polythene, low density 0.15 mm (0.15 mm)
Standard Wallboard Plasterboard (12.5 mm)
I'm trying to understand what the below rafter height would be based on the above. Would it be 12.5 mm plasterboard + a further 60.15 mm to accommodate the air layer/Hardrock multi-fix+Polyethylene? So a total of 72.65 mm below the rafters as the insulation (200mm) would fit within the rafter gap. Thanks
This is the roof makeup thus far
Clay Tiles 20mm
Breather membrane (0.1 mm)
Air layer/battens 30mm
Rafters 200 mm
To get to a .16 the U calculator at Rockwool for example has the following after the tile/membrane
HARDROCK® Multi-Fix (DD) (50 mm)
FLEXI® (200 mm)
Unventilated air layer (10 mm)
Polyethylene/polythene, low density 0.15 mm (0.15 mm)
Standard Wallboard Plasterboard (12.5 mm)
I'm trying to understand what the below rafter height would be based on the above. Would it be 12.5 mm plasterboard + a further 60.15 mm to accommodate the air layer/Hardrock multi-fix+Polyethylene? So a total of 72.65 mm below the rafters as the insulation (200mm) would fit within the rafter gap. Thanks