Speedy Builder5 | 02/01/2022 10:35:30 |
2878 forum posts 248 photos | I can't find any answer to my query on the net. Thinking of installing rock wool insulation in the loft of our 150 year old converted barn. There is an existing multi layer Al foil / expanded plastic roof lining which is meant to be equivalent to 240mm of glass fiber, but this is not adequate and in practice does not live up to its expectation. I am proposing installing 100mm rock wool fibre backed with craft paper attached which acts as the vapour barrier between the roof rafters. Rockwool passes fire tests etc BUT the craft paper burns like a torch - how can that be classed as fire resistant ? Bob |
Gordon Tarling | 02/01/2022 10:40:00 |
185 forum posts 4 photos | AFAIK, the craft paper layer is not the vapour barrier and is meant to be installed with that side away from the ceiling/plasterboard. G. |
john halfpenny | 02/01/2022 10:59:30 |
314 forum posts 28 photos | You have a 'warm' roof design (multi- layer insulation immediately under the tiles), so an additional vapour barrier ought not to be necessary. Possibly you already have foil backed plasterboard on the ceiling. If the roof space is sucking up heat, perhaps you have draughts around the roof edge keeping the roof space cold. I have the same kind of roof insulation and it works well at keeping the loft space (and main living area) tolerably warm and usable. |
Dave Halford | 02/01/2022 11:07:13 |
2536 forum posts 24 photos | Craft paper is not a vapour barrier either. There are other Rockwool products, one for ground floors has tissue on one face. |
noel shelley | 02/01/2022 11:19:40 |
2308 forum posts 33 photos | As John has said, I think I would be looking for WHY the insulation you have is not working well, it should, but drafts will soon spoil things. Good Luck Noel. |
Speedy Builder5 | 02/01/2022 11:59:36 |
2878 forum posts 248 photos | The multi layer insulation is now not favoured by several of the roofers around here, with temperatures of 40+ deg C in summer and -18 C in winter its not quite the same as the UK. Also, looking on the Rockwool site, the paper backing IS the vapour barrier and should be installed facing the installer. My original question was "the craft paper burns like a torch - how can that be classed as fire resistant ?" One of the intended uses of the product is for loft insulation where there would be no "Fire protection" from a 12mm plaster board lining. Just seems a little strange to me - perhaps like lining the outside of high rise buildings with certain products. Bob |
Bazyle | 02/01/2022 12:17:43 |
![]() 6956 forum posts 229 photos | The paper will have been treated with chemicals that reduce its flamability. By putting it at the bottom it is also encased between the rockwool and plaster so by the time it gets near a flame the wood laths and beams will be well away. As to foil insulation - well it gets tested in very controlled and hence artificial conditions which are nothing like real life so it meets building regulations and is a effective s the proverbial chocolate teapot. |
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