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Internal insulation of solid stone walls of period cottage

SuperHomes Revamp Forums General Discussion Internal insulation of solid stone walls of period cottage

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    Nicholas Verge

    I will shortly be modernising a small two-storey period cottage in Cornwall and would be grateful for any advice on choosing and installing internal insulation to the exterior facing walls.

    The cottage is in a terrace with similar properties either side and comprises an older part with a post-war extension. The older part is constructed of mortared slate slabs on the interior and exterior faces, with a presumed mortared rubble core. The walls of the more modern extension are concrete block and/or brick, possibly with a central cavity. Both parts have a pitched roof of slate.

    Exteriors of old and modern parts of the cottage are rendered, probably with cement, rather than lime mortar. Interior faces are painted or papered plaster.

    Currently, the cottage is heated by a single small open fireplace and a couple of electric storage heaters. Together these are not sufficient to keep the place comfortable during the colder months.

    Because an oil-fired or calor gas central heating system would be prohibitively expensive to install and run, to make and keep the place warm, I am proposing to insulate the cottage as best as is economically and practically possible, and to install an additional solid fuel stove (there is a unused flue available) +/- extra electric radiators and/or storage heaters. Hopefully this will suffice.

    I am thinking of installing internal insulation to the exterior facing walls, replacing existing windows with double-glazed ones and to install insulated palsterboard to the upstairs ceilings (+/- additional foambord between the joists in the loftspace.

    Regarding internal insulation of the walls, since cottage also needs to be completely rewired to modern standards which would ordinarily mean a lot of repairs to plasterwork afterwards,the plan is to install internal vapour impermeable PIR foamboard insulation to exterior facing walls using the “warm wall” method described on this site. Then to afix a free-standing stud frame internal of the insulation through which an electrician can route the wiring. Finally to install plasterboard over the stud framework.

    Does this sound feasible? Does anyone have any tips and advice from doing similar? Are there any problems with this proposal? Should any new wiring be run inside of the insualation or outside? Is it worthwhile also putting additional insulation (sheets of rockwool?) between the stud uprights and horizontals? What is the best method of fixing foamboard to the walls, glue or screws? Is it necessary to strip the existing plaster from the walls to be insulated to allow them to breath better (I am reluctant to do this as this would likely leave a very uneven wall to fix foamboard to)?

    Thank you kindly for your advice



    Nicholas – The Centre for Sustainable Technology in Wales have a lot of stone built cottages in area so will have some valuable experience to share on what works. They offer a free telephone advice service and may have a leaflet or book to offer on the subject. They may have some info on hemp/lime internal wall insulation trials for stone cottages and similar…

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