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Question on intrusiveness of Insulation retrofit for dormer bungalow

  • 20-10-2021 4:09am
    Registered Users Posts: 2,200 ✭✭✭ ajeganwalsh21

    Hi folks, I own a dormer bungalow, built approx 15 years ago that has a fairly shoddy insulation job in the roof, large parts are missing entirely.

    My questions are what is the best way to retrofit this with minimal intrusiveness?

    I.e. I don't want to rip off the roof or plasterboard or have to move out for two weeks.

    See the imgur album for pictures,

    Also, what sort of cost am I looking at?


  • Registered Users Posts: 1,760 ✭✭✭ dudley72

    If it was me spray foam insulation

  • Registered Users Posts: 255 ✭✭ Biker1

    Your best option is to strip everything back to the timbers. insulate between the rafters and knee wall studs with the appropriate materials, install airtight membrane and insulated slabs. Don't forget to leave a ventilation void between the felt and insulation on the sloped section. All horizontal areas can get 350mm standard loft roll.

  • Registered Users Posts: 30,666 ✭✭✭✭ listermint

    As above. You can do it right once or you can do it and leave bits of problems all over the shop. Which will 100 percent leave cold rooms or cold spots that catch moist air from just living and black mould spots.

    I'd bite the bullet . Depending on your skill level I'd do it myself room by room. Product like rafterloc is good for pitched roofs coupled with airtight membranes and importantly tapes.

    You could get someone in to board it all and plaster when done.

  • Registered Users Posts: 2,586 ✭✭✭ MicktheMan


    Couple / few things going on here;

    1. Your insulation is poor but I wouldn't be thinking sprayfoam ... define your thermal envelope first and then follow this with insulation (most likely fibre).
    2. Likely poor or no air tightness barriers installed ... this likely to be the big heat loss mechanism which will not be sorted by insulating.
    3. Ventilation?

    Maybe consider a proper heat loss survey to find and prioritise the issues at hand and present realistic / cost effective solutions.