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Heating and cooling: insulating diy thermal store

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  1.  
    • CommentAuthorjohnnyh
    • CommentTimeDec 22nd 2015
     
    Hi all,

    if anyone else out there has a homemade thermal store i would like to know how you insulated yours.
    mine has a wrap of glass fibre 170mm and i am trying to add a fairly well sealed polythene sheet on top of that to stop air movements.
  2.  
    my TS was a purpose made 2000ltr tank (conventional shape with my own spec. of connections) It came without insulation so I wrapped it in 3 layers or 100mm glass fibre as carefully as possible and then put a polythene sheet over. - So much the same as you have done.
    I have no idea what the standing losses are as it has been in use ever since. Now it supplies CH and DHW supplied to an adjcent 300ltr DHW tank and outside the heating season DHW only. (DHW is supplied by a HEX coil in the DHW tank)
    • CommentAuthorjohnnyh
    • CommentTimeDec 22nd 2015
     
    Thanks Peter. How have you sealed your polythene? I made a giant condom type thing (for want of a better word) to slip over the top of the store but the glue has not held very well so it's coming apart at the seams. After that is properly finished, i was thinking a layer of the new-fangled multi-layer insulation. It's got 20-odd layers of foam, foil, bubble-wrap etc but it is only 25mm thick.
  4.  
    I didn't seal the polythene, it has a good overlap at the sides, about 1m, then tied around and the top is folded, gathered together and tied, a bit like one end of a Christmas cracker.
    Being a farm the polythene is poly-tunnel plastic tied up with bailer twine :bigsmile:

    Polythene is not easy to glue, you have to use the specific glue/weld. When ploy-tunnels are put up here joins are made by welding with SWMBOs iron on a low setting (but don't tell her you are going to use it for this and certainly don't melt any of the plastic onto the iron otherwise it will make a mess of your shirts next time she irons them and that will be the least of your problems :bigsmile:)

    Do you know if the multilayer insulation would give any benefit over cost against say another 100 or 150mm of glass fibre?
    • CommentAuthorjohnnyh
    • CommentTimeDec 23rd 2015
     
    As i understand it the glass fibre is good for 2 out of 3 of radiation, conduction and convection. I can't remember which but it doesn't cope that well with one of them. The multi-layer is about all i've left room for round the back of the tank anyway but it is also not good at combatting one of the 3 heat losses, again can't remember which but remember it is a different one than the glass fibre. It has various layers including reflective layers so that is maybe where it does a different job to the fibre.

    i glued my giant plastic sheet contraceptive with a hot glue gun and it seemed to stick quite well but the stresses and strains of installing it was too much. If i used one of the two irons that we own for welding plastic i think she would say "oh! I've always wondered what they are for".
  6.  
    Posted By: Peter_in_HungaryIf i used one of the two irons that we own for welding plastic i think she would say "oh! I've always wondered what they are for"
    :bigsmile::bigsmile::bigsmile:
    • CommentAuthorEd Davies
    • CommentTimeDec 23rd 2015
     
    Separating out convection and conduction when you've got a lot of air around (e.g., tank with no insulation) is tricky: heat moves into the air mostly by conduction but then gets moved away mostly by convection. Air on its own, if there's no convection for some reason, is a pretty good insulator (i.e., it's a poor conductor of heat).

    Glass fibre mostly works by reducing the amount of convection that can happen. Still, if the temperature differences are big enough to kick off convection even through the little holes or there's enough external airflow (like in a well ventilated loft) air can move through the glass fibre. My understanding is that the main difference between good-quality low-conductivity mineral wool insulation and some of the cheap low-performance stuff is how well it's packed together to stop airflow.

    Glass fibre is also good at blocking radiation, of course. Still, if convection and conduction are getting some heat through the layer then radiation from the top surface will be significant so wrapping it in foil of some sort - which doesn't radiate as much (has a much lower emissivity) - seems like a good plan.
    • CommentAuthorjohnnyh
    • CommentTimeDec 24th 2015 edited
     
    Good to have some technical stuff Ed Davies. And yes Peter in Hungary, you should see my shirts, I have to pretend that i am too cool to be neat and tidy.
    •  
      CommentAuthorfostertom
    • CommentTimeDec 24th 2015 edited
     
    It's no good wrapping multifoil insulation round something solid - nothing like how it's meant to work (shiny bubblewrap maybe worthwhile). This is uncannily like how the famous Multifoil topic started on GBF!
    http://www.greenbuildingforum.co.uk/forum/index2.php?DATEIN=tpc_wlpssdlpg_1142805843
    • CommentAuthorEd Davies
    • CommentTimeDec 24th 2015
     
    Shiny foil is often used over mineral wool on commercial/industrial ducts for good reason. Multifoil might be a bit much for this application (unless you have some for free) but it would do some good.
  11.  
    Posted By: Ed DaviesShiny foil is often used over mineral wool on commercial/industrial ducts for good reason.

    I'm not sure whether the mechanical protection or the thermal qualities are more important in this application.

    Certainly when I wrapped my TS with ploy it was as much for mechanical protection as anything else as it is next to the boiler and I did not want to be brushing against it or have glass fiber bits drifting into the air
    • CommentAuthorjohnnyh
    • CommentTimeDec 24th 2015
     
    In fact there will be an air gap although imperfect. I have built a frame around the glass fibre to keep it in place and to attach the next layer to.
    •  
      CommentAuthorfostertom
    • CommentTimeDec 24th 2015
     
    Ah now you're talking
    • CommentAuthorcjard
    • CommentTimeDec 24th 2015
     
    Cardboard box round it then pour 2 part foam into the cavity...
    •  
      CommentAuthorSteamyTea
    • CommentTimeDec 24th 2015
     
    I just boxed my water cylinder with 100mm of celotext. Saves me about 2 kWh/day in losses.
    • CommentAuthorringi
    • CommentTimeDec 26th 2015
     
    Posted By: SteamyTeaI just boxed my water cylinder with 100mm of celotext. Saves me about 2 kWh/day in losses.


    How much insulation did it have before?

    Did you come up with an easy way of making the box from the celotext? (What about access to pipes and thermostat etc.)
    •  
      CommentAuthorSteamyTea
    • CommentTimeDec 26th 2015 edited
     
    Around 50mm before. Is a bog standard, 1987 vintage, 200 lt E7 cylinder.

    As it it is in an airing cupboard I just cut up section from 50mm sheet and made them fit. I did make up some triangles for the corner voids.

    I left a hole, but no main air path for the cabling/elements and stats.
    Only has 2 pipes, one at bottom that comes down the side, so that just got covered and one at the top, in the centre.
    I just made up two sheets to go either side and another to to go front to back.

    Not perfect by a long way, but so much better than it was before when I compared the heat loss figures.

    If I was building a house, I would probably build an oversize cupboard, insulate it well, then fit the cylinder, then insulate the door.

    Actually, I would, depending on how our old mate Jeremy get on, fit a SunAmp. They use vacuum panel insulation.
    • CommentAuthorjohnnyh
    • CommentTimeDec 29th 2015
     
    I like the idea of foam, Cjard but a rough calc of the 2 part foam required is about 0.5m3 which would cost a couple of hundred quid.
    •  
      CommentAuthorSteamyTea
    • CommentTimeDec 30th 2015
     
    Posted By: johnnyhcost a couple of hundred quid.
    I think I paid £25/sheet for the celotex. It was delivered.

    You can get 50 kg of PU for £200. That would be enough to do the neighbours houses as well.
    http://www.cfsnet.co.uk/acatalog/2_Part_Expanding_Foam_TDS.pdf
    • CommentAuthorcjard
    • CommentTimeJan 1st 2016
     
    Seconds n co for some cheap battered, wobbly wobbly kingspan, shaped into a box perhaps, then pour CFS's foam into the voids. 1kg of it apparently realises 1 cubic ft. A 1800 high 600 wide cylinder is 508 litres, the smallest containing cuboid is 648 litres and the 140 litre difference is 5 cubic ft.. A 50kg pack might well do a lot of neighbours..

    I'd still get the 50kg pack and then use it as many places as possible in the house. I'm finding a lot of uses for it in mine

    Or Fill the voids with £20 worth of concrete, same price as the foam but a higher heat capacity (get 140l of heat storage)
    • CommentAuthorjohnnyh
    • CommentTimeJan 8th 2016
     
    I reckoned i would need about 20 to 25 kilos for a 4 inch covering of my tank which is about 2.6m high and 1m diameter and i saw prices of £10 per kilo but £200 for 50kg sounds pretty good. Mind you, it doesn't keep more than a few months, or so i read, so if you don't need all 50 kilos then you'll have to find something to fill with the rest. Thats a lot of door and window surrounds!
    • CommentAuthorcjard
    • CommentTimeJan 13th 2016
     
    Interesting. I've had mine nearly a year and it still goes off like a rocket. I'll keep an eye on it and report back if it changes
    • CommentAuthorjohnnyh
    • CommentTimeJan 13th 2016
     
    Maybe the 4 month thing is just them covering their a**es.

    What do you do for mixing and cleaning up? I know that foam in a can is an absolute nightmare to clean up.

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