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Exrernal Cladding - Insulation query again

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  • 09-01-2006 3:40pm
    #1
    RedLady
    Closed Accounts Posts: 66 ✭✭


    Hi,

    A few weeks ago on About the House, they showed a house in Wexford that had put 350 mm of external cladding on their house. It was a Passive house and it looked like this type of insulation gave pretty oggd performance.
    Anybody have any experience of this? Is it expensive? Is it easy to maintain?
    Would it be better to use this than drylining an internal cavity wall?

    Regards

    Valerie


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    #2
    patrido
    Closed Accounts Posts: 299 ✭✭patrido


    Hi Valerie

    Kingspan make this (I'm sure others do too) and it's really just another version of all their other products - i.e. it gives the same thermal performance, for a given thickness, at more or less the same price. The kingspan product is TW53 (or K5). You basically fix a layer (or layers) of insulation to the outside of the main structure, and either plaster it or clad it with slates, wood, etc.

    The main structure of the house can be a normal cavity wall, timberframe, or even a solid wall (though in this case you'd have to provide for preventing moisture getting in, probably through a good vapour layer).

    The advantage is that you can put lots more insulation in without sacrificing internal room space, as you would with internal dry lining.

    You also maintain (or increase) the thermal mass within the thermal envelope of the building, assuming it's not a timber frame. This is very important if you are thinking along passive solar lines - though there is a lot more to passive solar than a few south facing windows and lots of insulation.

    It will also be easier to eliminate gaps in the insulation, and make it airtight (obviously apart from planned ventilation) - another potential drawback with dry lining.

    The downsides, as I see them are that your average builder will not have done this before, and while it's not rocket science, it might be wise to have an engineer who is familiar with it supervising things.

    Also, the main problem with increasing the insulation in walls, is that it widens the overall wall, and this introduces little complications and expenses that you wouldn't have with a standard wall. For example your foundations will probably need to be wider than standard and there may be issues with the roof, and with thermal bridging at the cavity closer, etc.

    It will also be a bit more expensive (purely in insulation terms) as it will take more insulation to cover the outside of a house than the inside.

    As for the expense, longevity and maintenance of the cladding itself... I don't know. But I would imagine that a wood cladding (like that beautiful finish on the house in the kingspan tekhaus literature) would require a lot of maintenance.


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