Hi
I have just had a leaky valley gutter repaired and large timber rafter replaced (leak was several years old and timber rotten). House is C1900 and 2nd storey room in roof (Vertial walls about 1m high then pitched) Roof is slate (no felt or membrane) with lathe and plaster. As there is currently a large section of plaster missing though it would be a good time to rip it all down and to insulate. Main Rafters (down Vallleys and across mid height of pitch) are 10" deep, but rafters that are plastered onto are 3"(75mm)x2". Looked at Kingspan info and it states 50mm gap for between and under insulation. If I use 70mm TP10 kingspan would the 5mm Plus the gap provided by the cross battening that the slates sit on, be enough ventialtion to prevent condensation.
Also TP10 insluation (for between) and K18 (for underrafter) both seem to have foil, surely foil is only needed on one as a vapour barrier?
Any help welcome.
I have just had a leaky valley gutter repaired and large timber rafter replaced (leak was several years old and timber rotten). House is C1900 and 2nd storey room in roof (Vertial walls about 1m high then pitched) Roof is slate (no felt or membrane) with lathe and plaster. As there is currently a large section of plaster missing though it would be a good time to rip it all down and to insulate. Main Rafters (down Vallleys and across mid height of pitch) are 10" deep, but rafters that are plastered onto are 3"(75mm)x2". Looked at Kingspan info and it states 50mm gap for between and under insulation. If I use 70mm TP10 kingspan would the 5mm Plus the gap provided by the cross battening that the slates sit on, be enough ventialtion to prevent condensation.
Also TP10 insluation (for between) and K18 (for underrafter) both seem to have foil, surely foil is only needed on one as a vapour barrier?
Any help welcome.