kxi

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  1. kxi

    Re-bar

    I was concerned about the long-term durability of standard steel rebar, so looked into alternatives a bit. My layperson's summary below. However, I'm now just going to use standard steel in our own Reinforced Concrete parts. While steel corrosion seems a major problem for structures like bridges, dams, etc, my SE has assured me any RC with standard rebar kept protected from; the elements, unusual chemicals, and cyclical loading should be fine for over 150 years. I.e. ours will be fine, and I'd guess anything inside ICF also fine. As below, all the alternatives have some disadvantages. But if you are building something with exposed RC and care about it lasting more than 50 years, the lifecycle costs seem to suggest everything is more cost-effective than using standard steel. Some evidence of standard steel / iron reinforcement durability: The first RC house ever built 1852 is still standing https://en.wikipedia.org/wiki/François_Coignet The first one in the US 1876 is apparently fine https://en.wikipedia.org/wiki/William_E._Ward_House The first RC skyscraper 1903 is also apparently fine https://en.wikipedia.org/wiki/Ingalls_Building Alternatives: (Some comparison here https://www.usbr.gov/research/projects/download_product.cfm?id=2493 ) Stainless steel A fairly straightforward replacement for normal rebar (though apparently, you need to use a bit more to get the stiffness) and used for many years. Main issue is the cost, which might be 3 or more times the cost of normal rebar. I didn't check the specific price. Glass Fibre Reinforced Polymer GFRP Proposed as a corrosion-free alternative to steel and much lighter, with higher tensile strength. Has been well studied and increasingly in use in some structures worldwide, and has building codes that govern its safe use. Unfortunately, it's not without problems: Fire - while the glass withstands very high temperature, it's in resin that softens at over 150 C. For this reason, the Institution of Structural Engineers do not recommend it for situations in which fire is a concern. Unknown long term behaviour in concrete - glass doesn't like alkali i.e. concrete, or moisture, and as per one of the suppliers' own descriptions "At this time, there is no consensus as to what would be an accurate service life prediction model for the use of GFRP bars". http://www.aslanfrp.com/media/aslan100.pdf Creep - This same supplier also notes that GFRP has creep rupture with sustained high utilization. Though these are AFAIK accounted for in the building codes that apply to GFRP. My SE also noted its long term creep is not good. Elasticity - much more elastic than steel and so requires more reinforcement or more concrete depth to compensate. Perhaps of note Owens Corning recently bought the manufacturer of Aslan GFRP, so presumably they think it has long term potential. Carbon Fibre Reinforced Polymer CFRP Really good, really expensive, doesn't like fire. Basalt Fibre Reinforced Polymer BFRP A new contender that has only been in use for a few years, and the subject of much current research especially in China. Similar properties to GFRP (light, high tensile strength) but may address some of the issues with GFRP and appears to be able to be produced more cheaply e.g. in the US you can get rolls at $6.60 a metre, and Gatorbar claim cost parity with standard steel. https://www.neuvokascorp.com/sites/all/themes/theme923/pdf/GatorBar_data_20160907_HIGH.pdf BUT it shares GFRP's disadvantages in that The resin doesn't like fire Still elastic The major drawback is that it's so new, people seem nervous about doing anything structural with it: There's almost no example of it being used in house construction other than floors & shallow foundations Gatorbar currently limit use to slab on grade and low walls/foundations (confirmed this with them) UK suppliers of Galen's Rockbar (Magmatech) said it hadn't been used structurally and any structural use of it would have to be approved by an SE Various BFRP references: http://www.thestructuralengineer.info/onlinelibrary/pdfs/SustainabilityMasterBuilder_Sep10.pdf https://www.ripublication.com/ijaer18/ijaerv13n8_37.pdf https://livrepository.liverpool.ac.uk/16333/4/SalhLuna_Feb2014_16333.pdf http://www.carnationconstruction.com/Materials/01-Materials-Rebar.html https://www.sciencedirect.com/science/article/pii/S187661021730022X https://www.monolithic.org/link-to/basalt-fiber-rebar https://smarter-building-systems.com/smarter-building-basalt-faqs/ https://www.researchgate.net/publication/315642749_Investigation_of_Structural_Members_with_Basalt_Rebar_Reinforcement_as_an_Effective_Alternative_of_Standard_Steel_Rebar https://pure.qub.ac.uk/portal/files/154263432/180620_polymers_10_00678_paper_accepted_in_J_of_Polymer.pdf BFRP durability: https://www.sciencedirect.com/science/article/pii/S0264127518308724 https://www.researchgate.net/publication/319943787_A_refined_prediction_method_for_the_long-term_performance_of_BFRP_bars_serviced_in_field_environments https://ascelibrary.org/doi/pdf/10.1061/(ASCE)CC.1943-5614.0000497 Some BFRP suppliers: https://www.neuvokascorp.com/sites/all/themes/theme923/pdf/GatorBar_data_20160907_HIGH.pdf http://magmatech.co.uk/products/rockbar/ http://orlimex.co.uk/composites/ https://www.monolithicmarketplace.com/collections/basalt-rebar-products/products/rebar-12mm-diameter http://galencomposite.com/products/composite-reinforcement-rockbar/
  2. kxi

    Insulated roofing sheets

    @Simon Brooke Ok, good luck.
  3. kxi

    Lignacite block

    @Russell griffiths I suspect it's a question of the market you are catering for. The Shard used 140,000 of them, presumably because in the context of a project like that, being able to say the blocks were carbon neutral was worth more to them than an extra £140k (or whatever it was). http://www.lignacite.co.uk/project-library/the-shard-2.html The blocks also seem to have a slightly better acoustic reduction than standard medium weight, but perhaps not a big factor in most cases.
  4. kxi

    Insulated roofing sheets

    @Simon Brooke Have you had an airtightness test yet to see how the taped kingspan panels perform?
  5. kxi

    Lignacite block

    Does anyone have experience with / opinions on the Lignacite block from Lignacite? http://www.lignacite.co.uk/concrete-and-facing-masonry-blocks/concrete-blocks/medium-dense/lignacite.html Data sheet http://lignacite.co.uk/component/edocman/?task=document.viewdoc&id=128&Itemid= Medium weight concrete block with 48% recycled aggregate including recycled wood, allowing them to claim the block's carbon footprint is -2kg per tonne. Used extensively at The Shard and London Olympic stadium (among other places).
  6. kxi

    Bungalow Barn - update

    @Snowbeetle excellent, thanks very much.
  7. kxi

    Bungalow Barn - update

    @Snowbeetle How did you find installing the geocell? Any tips / things you would do differently if doing again?
  8. From an initial look appears superior to stainless - thanks very much.
  9. I believe part of the problem is many concrete structures will likely not last anywhere near as long, mainly due to corrosion of the steel reinforcement - which the romans didn't use. See https://theconversation.com/the-problem-with-reinforced-concrete-56078 Thinking about our own build (rather than bridges, skyscrapers, etc) our SE says if kept dry and protected, any reinforced concrete should last 'a long time' so it shouldn't be an issue. However, given we're aspiring to a design life of more than 150 years I'm keen to explore options to reduce the risk, given re-inforced concrete will form crucial parts of the structure. Replacement of any steel rebar with stainless steel looks like a realistic alternative, with really a fairly small cost considering it might (?) double the life of the structural element, though TBH I've not investigated yet. Basalt another option. Roman concrete also superior to modern due to their use of volcanic ash https://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/15190/The-Secret-Ingredient-in-Ancient-Roman-Concrete-is-Seawater.aspx Concrete block is another matter and there's a variety of possibly more sustainable options such as types made by http://www.lignacite.co.uk/ but I've not looked into that fully either.
  10. kxi

    Framework EcoSteel

    Back on Ecosteel, from the illustrations the steelwork appears to completely bridge the SIPs, which slot into the beam. I'd have thought this almost completely cancels out the insulation and also a condensation risk. The steels look like they are then covered internally with something like OSB, which would not do well with any condensation. Odd why they don't wrap the frame externally as is standard for sandwich panels. Insulated panels external to a frame (perhaps steel) I think still deserves a look, but this particular design seems a bit suspect to me.
  11. kxi

    Hello from Berkshire

    @Ferdinand yes that marked part is part of the plot, as well as another garden area to the east, also a decent curtilage around the whole building to allow for maintenance. Various covenants in place with the farm for access, services, etc. The woodland 'just out of shot' to the left of that model picture is under a long-term woodland management grant, and the whole area is green belt, so in the event of everything changing hands in years to come, the new owners shouldn't have to worry about their north view being onto an abattoir. Class Q has been a bit tricky, but on a firmer footing with the recent updates about structure. Martin Goodall's blog has been essential. The planners are (now) happy with the design, and I think we've got a good relationship with the planning dept. Further amendments to include stainless steel cladding might be a step too far though. If it's ever of interest to anyone, the GPDO does explicitly allow making design amendments to a previous class Q agricultural conversion PD, though councils may not initially know this is possible.
  12. kxi

    Insulated roofing sheets

    @Simon Brooke Thanks very much. Looks fantastic. To clarify - you just taped the joins? (I.e. pro clima tape, not the additional membrane). Isocab have similar quadcore panels (they are part of kingspan I think) and say that when joints are ‘finished’ they give <0.04 m3/hm2 at 50pa http://www.ecohomepanel.com/brochure_en/18/ which suggests it's doable. If you are putting a ceiling up under them, I suppose you could add some mineral wool in between the rafters/purlins if the noise was bothersome. What have you done/plan to do for the wall build-up, as I assume insulation will be internal? I couldn't see any quad core sheets available. They do do the karrier wall panels, but that seems an expensive approach inside a wall.
  13. kxi

    Hello from Berkshire

    @Ferdinand Regarding the opposite walls, there's definitely some thinking to do here, but I'd mentally put it in a 'once we are finished' box. One idea was to add climbing plants, though the snag is they would be very shaded. This might be partly mitigated by cladding the house south face with stainless steel to reflect light from our south face onto the opposing side. This might not be effective or desirable though. Also the shed walls are made of white & blue asbestos fibre-cement, so I would not want anyone having to interact with them (e.g. for plant pruning), as any contact with the surface could in theory release fibres. The continuing presence of so many of these ageing, potentially lethal panels is something to be reviewed, but it would be a major undertaking to replace them. "Grand Designs last week had one of those that worked spectacularly well by being aligned carefully with the internal spaces of the room." Aha thanks, I'll take a look. It means the north rooms get light from two aspects, which is nice. How to operate the blinds/curtains over the bedroom ones is a slight snag but i'm sure can be solved. "Is there any scope for inside/outside living (eg Franch Doors) on the more attractive North side? I do not see that in the model, or perhaps I missed it." On the west end there is a first floor terrace within the original walls (see 3rd model image) with large doors/windows into the main living area. This terrace looks out over the future garden & trees to the north, then the farmyard & other buildings to the west and south. These last are perhaps not everyone's idea of a good view, but it does get the sun & sunset and various birds like wheeling around the yard at certain times of the day. A north terrace would certainly get a better view, but is currently a no-go from a planning POV as it extends the existing footprint. It would also be shaded all the time as it's north facing (but that might be fine). A deck at the east end also would have a nice view and get the morning sun, but again not allowed under current planning regulations.
  14. kxi

    Insulated roofing sheets

    @Simon Brooke. This is one of the arrangements we are considering, so very keen to hear how you got on. 1. Are you just using the panel seals for airtightness, or did you add something else e.g. taping/sealing the joints? How has that worked out? 2. Did you add any additional vapour control below, or just rely on the panels? 3. How is the acoustic? Have you got anything else underneath it before the internal? (One of our options is to have it exposed bare). 4. Did you look at the 147mm kingzip insulated panels as an alternative? Only 0.15 u value, so I assume you went with the KS1000 for U value reasons. Annoyingly they don't do the kingzip in quadcore, though the website doesn't mention quadcore for the ks1000 either.
  15. kxi

    Hello from Berkshire

    @vivienz One of the designs that we didn't go for, and turns out wouldn't have been allowed by planners anyway as involved a bulk increase, was a thin full-length clerestory for summer-shaded south light, which I think would have looked great (if you could fly).