Outbuilding insulation - is just the roof space enough

Discussion in 'Eco Talk' started by Albs123, Jul 24, 2021.

  1. Albs123

    Albs123 New Member

    Hi All,

    I have a separate outbuilding at my property that is double skin brick construction with no cavity. Inside the previous owners have dot & dabbed and plastered but they never installed any insulation when doing this, and as a result it is unusable in the depths of winter.

    I’d like to install some insulation but I’m reluctant to rip all the existing boards down and re-do it all. There is access to the roof space and I can see there’s also no insulation in there. If I installed some say 300mm wool insulation up there, would that be enough to keep the place warm without insulating the walls too? Room is about 15m2.

  2. Abrickie

    Abrickie Screwfix Select

  3. Jimbo

    Jimbo Screwfix Select

    The heat loss is everywhere and proportional to the surface area (and thermal conductivity of the component). So the walls are likely the largest source of loss. The ceiling will help, but tbh if you want it usable bite the bullet and pull out the dot-and-dab and redo it with either foam backed board or batten the walls and fit 25mm celotex sheets between the battens and plasterboard on top. The first inch is the most important!

    Consider also moisture ingress, presumably there is a DPC? If it's rendered and painted should be fine as-is, if bare brick one option is to paint the bricks with a brick water sealer - try the builders forum for more advice on that.

    Ceiling wise 300mm wool should be more than adequate. It's diminishing returns, even 4" will dramatically reduce the heat loss.

    For the floor it's less easy. Presumably it's bare concrete. A thick carpet tile will give you something, or could lay a floating chipboard floor on 25mm celotex sheets then e.g. laminate over the top, but it will obviously bring the floor up nearly 2 inches. Could also consider vacuum panels under chipboard floating floor but v expensive - will reduce the buildup by 15mm though.

    Another option is 10mm foam tile backer boards then lay a tiled floor directly on top, maybe with an electric under floor heating wire set to say 18°C just to keep the chill off the floor. Or finally just a carpet with e.g. Cloud Nine 11mm underlay.

    Depending on the size of the building and the amount of time you're planning to spend in it, a small heat-pump might be the most cost effective solution in the end, like this:

    Even a system like that will use 1/3rd of the electricity compared to a resistive electric heater. More expensive split systems can be twice as efficient, but need professional installation so end up being twice the price. Either will do cooling in summer too.
  4. stevie22

    stevie22 Screwfix Select

    The ceiling is the easiest, cheapest and best place to insulate. Don't forget heat rises.

    There are huge number of houses that have solid walls and with no insulation except maybe a bit in the roof and people live in them.

    What do you want the outbuilding for? All you got to do is pump heat in quickly enough. Give the ceiling try and see how it goes: even if you do more this work won't be wasted,
  5. GS63

    GS63 New Member

    Definitely sort the floor - standing on bare concrete during the winter is a sure fire way to get really cold.

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