BISF house insulation

[martynfogg]

Hello,

I own a BISF house, essentially a steel frame prefab. The steel frame is covered with sheet metal cladding and/or render on the outside and stud wall on the inside.

What would be the best way to add or increase wall insulation?

Thanks,


Martyn

[Simonhayes]

I own one of these houses too and I am wondering about increasing the insulation in the walls. If you take the plasterboard off on the inside of the wall you will see that there is rock wool insulation hanging inbetween the framework. It is tempting to just get some thicker rock wool insulation and just pack the void out. However I am concerned that this could cause the timber and metal frame to 'sweat' if water vapour gets in and this could lead to rot/rust. At the moment the thin insulation allows air to circulate.

I am not an expert, but if you ever get any guidance from an expert, perhaps you could let me know. At this point I would suggest that the best way to insulate the walls would be to replace the pasterboard with some new plasterboard that has insulation fixed to it, I think its called Jablite. Infact rather than removing your existing wall covering, you can probably fix Jablite to the existing wall.

[martynfogg]

Simon.

Thanks for the reply. I had the same concern as you about adding to the 'cavity' insulation, I think it may form a bridge for moisture which would be lethal for the metal frame.

Other options I have considered are an external cladding with integral insulation, which is expensive, or dry lining all the walls. Insulated plasterboard would be good, although I think Jablite is just insulation, you have to plasterboard on top of that.

If I get any good advice or other info, I'll post here. It's good to get in touch with other BISF owners. I'm in Bath, where there are around 20 BISF houses (to my knowledge), although mostly Housing Authority owned. Whereabouts are you?

Martyn

[noseyparker]

guys, you are both right to be concerned about condensation forming in the cavity if you change the insulation. dont have any experience of these houses in particular, but if you were to increase the insulation you may also need to get the work checked and signed off by the Council's building control dept. as the work is covered by building regulations.


you would certainly need a vapour barrier if you were taking the plasterboard off and increasing the insulation behind it; this could be as simple as using foil backed plasterboard, or fixng polythene sheeting on the room side of the insulation and beneath the plasterboard. you could consider using an insulating plasterboard (polyurethane foam on the back of it), or lining on the room side of the existing plasterboard with "Sempertap" from Mould Growth Consultants Ltd. which is itself a vapour barrier. You may need to provide some ventilation into the cavity too.

strongly recommended that you get some expert advice from specialists on what to do, before you do it. should not be insurmountable. but "interstitial" condensation - when it forms in the cavity - can be very damaging, causing wood rot (rust in a BISF house?) etc.