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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    The house we just bought has a newish hot water cylinder in the unheated loft, with the usual layer of foam insulation factory-fitted, about 50mm thick. Not what I would have chosen, but we won't be changing it anytime soon.

    According to the manufacturer, it has standing losses of 65W (1.5kWh/d). This will add up over time to quite a lot of waste, so I'd like to add lots more insulation.

    As there's no shortage of space, I was thinking of wrapping it with lots of loft roll, there's some handy spare roll in the loft. Maybe add 400mm thk of mineral wool.

    Has anyone done this? Any pitfalls? How to hold it in place? Does it need to be removable?
    I think the only issue is that you mustn't cover the plastic back of any immersion heaters. Maybe look at rockwool that is covered in foil so the insulation can be easily taped together and to the cylinder. It's also worth covering any pipework to and from the cylinder.
    • CommentAuthortony
    • CommentTimeJan 10th 2020 edited
    Go for it, more insulation will reduce heat losses but they can never be eliminated
    • CommentTimeJan 10th 2020
    I've wrapped our thermal store with loft roll (recycled plastic so it's not itchy). As PoS said, don't cover immersions or in my case the pump and control unit as well.

    My thermal store is in a cupboard so the insulation is mostly held in place by the cupboard walls but I did tape together the front. It needs continual attention, because the tape doesn't stay stuck. I haven't tried any Sicrall or similar yet. If you have access all round, I'd suggest instead to tie it in place with loops of string round the tank.

    Yes, you will need to remove it if (when) there's a problem with the tank or plumbing.
    • CommentAuthorHats
    • CommentTimeJan 10th 2020
    Wrapped mine in rock wool and then built a 75mm Calotex box round that all foamed and taped. left the heater element area accessible. That was 5 years ago and it works great even the overflow pipe gets hot as there is nowhere else for the heat to go !
    • CommentAuthorRobL
    • CommentTimeJan 10th 2020
    Ours is in a cupboard too - we fitted Xps between it and the nearest walls, used squirty foam to hold it all in place.
    Then poured a bean bag poly balls down the back between the outside wall and it.
    If ever we had to remove it, i guess Id cut the squirty foam to remove the xps, and vacuum up the mess of poly beads.
    • CommentAuthortony
    • CommentTimeJan 10th 2020
    • CommentAuthorborpin
    • CommentTimeJan 13th 2020
    Don't forget the pipes.

    I've double layered my pipes with EPDM insulation. Makes a huge difference.
    • CommentAuthortony
    • CommentTimeJan 13th 2020
    • CommentAuthorCliff Pope
    • CommentTimeJan 15th 2020
    We've got an old-fashioned airing cupboard for storing bed linen etc. Originally it had an uninsulated cylinder, but even with a bit of thin plastic-wrapped foam tied round the cupboard was always very warm. It was useful for germinating pips - I successfully germinated a coconut once.
    Then when we had to replace the cylinder I fitted the factory-insulated kind. It must be working well because the cupboard is chilly and now useless for airing things!

    I did modify the pipework having read a lot about heat losses along pipes through local thermo-syphon circulation within a single pipe. All vertical pipes should have a minimum horizontal run from the tank first of at least 2', including the vent pipe, and be well insulated of course.
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