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Housing - Renovation: Most eco loft insulation

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  1.  
    • CommentAuthorneelpeel
    • CommentTimeAug 7th 2022 edited
     
    I'm going to help someone topping up their loft insulation and filling in the many metres of gaps. I will need to fill up the battened walls and much of the floor in the eaves.
    They are keen to use sheeps wool insulation as the assumption is that it's the greenest option. There was discussion on this umpteen years ago on the forum, but what are the thoughts these days? Any new eco wonder products around?
  2.  
    Search sheep's wool and it will give you much re moths but little on whether the currently-manufactured product is deemed to suffer from unwanted moth attention, I think. I know people who have had issues a long time ago, and I know many who have not. None of the sheep's wool installations I have done has, to my knowledge, succumbed.

    How about recycled cotton? Pavatex sell it. Not sure if others do in the UK. If you don't mind loose-fill how about recyc newspaper (Warmcel or similar - (?)Isofloc?). Obv difficult for stud walls but you could always membrane the stud wall on the back side to a height where you can scoop in the Warmcel, then finish the last but with a 'Green' quilt of your choice.

    Eco wonder products? Probably not!
    • CommentAuthortony
    • CommentTimeAug 7th 2022
     
    I consider money a resource not to be wasted, and time

    I use fibreglass whenever I can, cheapest and easy to use, often now has high recycled content. Eco wool is so nice now that it isn’t itchy.

    Seen and heard too many problems with moths and sheeps wool plus I can’t afford it.
    • CommentAuthorneelpeel
    • CommentTimeAug 7th 2022
     
    Reading about moth potential is putting me off the wool idea. Especially as there has apparently been issues with moths in the loft before.
    Non-itch glass wool? Is that just certain brands? I used to hate the stuff but not used it for a good few years.
    • CommentAuthorMike1
    • CommentTimeAug 7th 2022 edited
     
    Posted By: Nick ParsonsSearch sheep's wool and it will give you much re moths but little on whether the currently-manufactured product is deemed to suffer from unwanted moth attention, I think.

    The last I heard was from 2010, that the effectiveness of treating wool with borax (the favoured treatment against insects) 'seems to be uncertain':
    https://www.exmoor-nationalpark.gov.uk/__data/assets/pdf_file/0025/221578/EB63-Ecos-Trust-2010-Audit-of-Local-Sustainable-Construction-Materials-in-the-Greater-Exmoor-Area.pdf
    Unless anyone had an update on that?

    For a natural insulation, personally I'd choose hemp. Apart from its good insulating properties, growing it also locks up CO2, rather than - like sheep - causing methane emissions (albeit it can be argued that wool's a waste product).

    For a non-natural product, I've previously chosen recycled plastic quilt.
  6.  
    Another vote for recycled glass wool, if there is enough space to put enough thickness in. For each unit of insulation value, it has less impact than all others over its whole lifecycle, including production, treatments, transportation and eventual decomposition. Knauf do a 0.032 one.

    If you are tight for space, such as behind wall linings, then phenolic. It's not eco to use insulation that doesn't insulate enough!

    Obvs be mindful of condensation issues and vapour barriers, it's also not eco to install insulation that will get damp and need replacing only a few years later.

    Anything organic will make methane when eventually landfilled.

    Other considerations: Fire resistance? Easy fitting without gaps? Breathability? Wind-washing? Mouse proofness?

    https://www.greenspec.co.uk/building-design/embodied-carbon-of-insulation/
    • CommentAuthorMike1
    • CommentTimeAug 8th 2022 edited
     
    Posted By: WillInAberdeenrecycled glass wool... For each unit of insulation value, it has less impact than all others over its whole lifecycle
    An interesting statistic and although (since emissions over the next 3 or 4 decades are the most critical) embodied carbon is the priority, I'd be interested to see a product comparison.

    In terms of embodied carbon, the most recent information I can spot - March this year - is the 'The City of Nelson Material Carbon Emissions Guide' https://www.nelson.ca/documentcenter/view/5583 which, for a 100m² home with an element resistance of R-13 (Canadian system, so U-value presumably 0.077) gives the following embodied carbon figures (among others) for wall & roof insulation products at the factory gate, in kg of CO2e / m²:

    Mineral wool batt: +300 to +916 (average +608)
    Wool batt: +296
    Fiberglass batt: +106 to +215 (average +154)
    Hemp fiber batt: -182
    Cellulose batt: -466
    Wood fiber batt: -710 to -386 (average -566)
    Hempcrete: -1,676 to -969 (average -1,142)
    Straw bale: -1,957

    Obviously the situation & manufacturers in Canada are somewhat different to the UK, but the figures are interesting.
    •  
      CommentAuthordjh
    • CommentTimeAug 8th 2022
     
    Posted By: Mike1Hemp fiber batt: -182
    Hempcrete: -1,676 to -969 (average -1,142)

    I don't understand these two figures. I understand that a hemp batt is negative since it sequesters carbon. But hempcrete is a mixture of hemp and lime, so ought to be significantly worse than hemp batt to my simple brain, not 5 to 9 times better! What am I missing?
  9.  
    Hi Mike, see pic attached, derived from the ICE database which seems fairly reliable
    https://www.greenspec.co.uk/building-design/embodied-carbon-of-insulation/

    They make the point that the manufacturers of organic insulants will advertise only their manufacturing emissions, which they claim are negative because of the carbon absorbed by the growing hemp/wood/sheep etc. They conspicuously omit the end of life decomposition when all that carbon will be emitted as CO2, or Methane if the building rubble is landfilled. As the carbon will not have been sequestered in the insulation for anything like geological timespan, then that approach is "controversial"! This pic excludes the organic carbon content.

    Woodfibre seems to be manufactured in Central or Northern Europe, and is pretty heavy, so the transportation emissions will be significant. But unaccounted here too. Don't know where hemp/crete is transported from.
      Screenshot_20220808-164737.png
  10.  
    Posted By: djhhempcrete is a mixture of hemp and lime, so ought to be significantly worse than hemp batt to my simple brain, not 5 to 9 times better! What am I missing?

    It's a calculation dodge, as follows:

    -The number quoted is based on achieving R = 13
    -Hempcrete is worse insulation than hemp batt, so we need a thicker layer of hempcrete to achieve R=13
    -So we use many more kg of hempcrete than of batt
    -So even though each kg of hempcrete "sequesters" (temporarily) fewer kg of CO2 than a kg of batt, because we are using many more kg of hempcrete, overall it is made out to look better than batt.

    If we believed that hemp really sequesters CO2, then it would look advantageous to use as much of it as we possibly could. EG dig a huge hole in the garden and pour hempcrete into it, until we have used enough to "offset" all the lifetime emissions of the building and all its occupants!

    However if we look at the whole lifecycle emissions (including decomposition and transport as well as manufacturing) then that idea seems much less attractive... That's the problem with manufacturers quoting only the cradle-to-factory-gate numbers!

    Edit: it would be nice if there were a standardised way of doing these building LCAs so the claims were comparable and verifiable, I'd like to see that set out in building regs.
    •  
      CommentAuthordjh
    • CommentTimeAug 8th 2022
     
    Posted By: WillInAberdeen
    Posted By: djhhempcrete is a mixture of hemp and lime, so ought to be significantly worse than hemp batt to my simple brain, not 5 to 9 times better! What am I missing?

    It's a calculation dodge, as follows:

    -The number quoted is based on achieving R = 13
    -Hempcrete is worse insulation than hemp batt, so we need a thicker layer of hempcrete to achieve R=13
    -So we use many more kg of hempcrete than of batt
    -So even though each kg of hempcrete "sequesters" (temporarily) fewer kg of CO2 than a kg of batt, because we are using many more kg of hempcrete, overall it is made out to look better than batt.
    Yes, I can see the argument but I can't make myself believe it. There's even more lime than there is hemp, so things should be getting worse? It seems weird that deliberately building with a 'worse' material can give a 'better' result.

    If we believed that hemp really sequesters CO2, then it would look advantageous to use as much of it as we possibly could. EG dig a huge hole in the garden and pour hempcrete into it, until we have used enough to "offset" all the lifetime emissions of the building and all its occupants!
    As Mike said, it might be acceptable to consider a 30-year or so time period given the present emergency so cradle-to-gate might be considered acceptable (I'm not defending that point though). But if I was going to dig a big hole in the garden, I would fill it with sealed plastic bags filled with hemp (ideally vacuum evacuated and better filled with straw). Alternatively of course you could fill the hole with water and hemp/straw and call it a peat bog. They sequester carbon quite well I believe. :bigsmile:
    • CommentAuthorMike1
    • CommentTimeAug 8th 2022 edited
     
    Posted By: WillInAberdeenHi Mike, see pic attached, derived from the ICE database which seems fairly reliable
    Thanks - yes it should be, though who knows what the end-of-life provision will be in 50/75/100 years time!

    Posted By: WillInAberdeenWoodfibre seems to be manufactured in Central or Northern Europe, and is pretty heavy, so the transportation emissions will be significant.
    Volume is probably a more important factor, especially if most of the transport is by sea. There's another thread...

    Posted By: WillInAberdeenDon't know where hemp/crete is transported from
    Hopefully locally - or at least regionally - grown hemp and mixed on site, so the lime would be the main concern.

    Posted By: djhThere's even more lime than there is hemp
    For walls, 36 to 44kg of lime to 20kg hemp = 200L hempcrete...
    If it's a structural element, it may also be offsetting bricks & blocks (though not in the calculations quoted)

    Posted By: WillInAberdeenIf we believed that hemp really sequesters CO2, then it would look advantageous to use as much of it as we possibly could. EG dig a huge hole in the garden and pour hempcrete into it...
    Closer to the truth than you might think - burying trees to sequester carbon has been seriously proposed!
    https://cbmjournal.biomedcentral.com/articles/10.1186/1750-0680-3-1

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