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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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Offers and wants: £3 a roll insulation and free monitor

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1 to 16 of 16

  1.  
    • CommentAuthorCWatters
    • CommentTimeJan 18th 2011 edited
     
    Leaflet through the door from nPower today..

    £3 a roll and a free energy monitor if you buy 7 rolls before 15th Feb

    http://www.npower.com/web/diyloftinsulation/index.htm
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 18th 2011 edited
     
    Any good reason not to top my insulation up to (up to) 400mm with this that you can think of? (Loading on plasterboard, legal, etc, etc?) I don't think that I actually hit 270mm consistently across the entire loft at the mo.

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 18th 2011 edited
     
    You have checked and de-rated any cables up there, regardless of their current load.
    Also worth checking any pipework, better to find a potential problem with only 270mm of sodden insulation to remove rather than 400mm :wink:
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 18th 2011
     
    We're running on a fraction of the designed load for cables, and there is no pipework up there at all.

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 18th 2011 edited
     
    The circuit must still be de-rated regardless of the load, you have the tables don't you?:bigsmile:
    That will include your PV ones too.
  6.  
    S.T.- Where is the best place for cables, under insulation to ensure any heat generated is returned to home or above insulation to ensure dissipation to atmosphere. Would be interesting to know operational experience of current installers.
    Rgds
    Brian
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 18th 2011
     
    Above and in free air. If the cable is warming up then it is getting dangerous and if it is in the loft then little use for house heating. There is a whole section in the regulations about loft wiring. And now someone is going to ask me to look it up :devil:
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 18th 2011
     
    Feel free to look it up ST.

    But as I say, lighting circuits originally used for 60W or 100W loads per fitting are now running at under 20W each, and only for relatively short periods. I should be amazed if I'm anywhere near dangerous.

    Not entirely sure where socket wiring runs but again we have very low loads upstairs except brief ones such as hair-drier or vacuum cleaner or now an occasional dehumidifier run.

    Clearly, if we get upstairs rewired then I'll do the right thing.

    As to the PV wiring, yes, I hear you, but it runs vertically down and I had the installers seriously over-rate it by my metric. What was ~3.3kWp was moved onto a new *much* fatter cable and the new 1.2kWp on to the original circuit. Again, I'll be amazed if we're anything than massively conservative. Can't remember the wire sizing, but I could dig it out I suppose.

    It's squirrels that I worry about.

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 18th 2011
     
    Right, here we go, shame we cant make tables on here, so a triple space is the next column.
    Circuits have to be de-rated regardless of their load and anyone installing insulation becomes personally liable.

    Length of thermal insulation (mm) Derating factor
    50 0.88
    100 0.87
    200 0.63
    400 0.51

    This is applicable for any part of the cable that passes through or is under (between plasterboard/joists,boards) insulation. So even if it only goes though 2 inches of insulation and the rest is in still air it must be de-rated to 0.88 (88%) of the design load.

    So if you are intending to fit 400mm of loft insulation AND the cables run under OR though it then you MUST de-rate to 0.51 (51%) of the design load. Usually lighting circuit are 5 amp so you will have to put a 2.5 amp circuit breaker or fuse in that circuit regardless of the load currently placed on them.

    The PV side will be exactly the same, work out the design load and the then de-rate depending on how far it travels though the insulation.

    There are also rules to where and how cables can be fitted and clipped, and how they pass through joists, just to add to the fun.

    Is there a MUST in programming, wish there was at it would save a lot of wasted time debugging :devil:
  10.  
    Monitors are warmth-loving creatures - presumably why you need the cheap insulation to go with your free one. But won't the poor thing be itchy from that horrible glass-fibre?
    •  
      CommentAuthorDamonHD
    • CommentTimeJan 18th 2011
     
    NP: I will review and pass on the free monitor: itchy or not it will be horribly confused by our PV microgeneration.

    ST: I hear what you say. I will review and may do some down-rating of CBs, though since all the current insulation was in place when we had the current brand-new consumer board and CBs fitted, and a full electrical inspection, some of that may already have been factored in.

    Rgds

    Damon
    • CommentAuthorCWatters
    • CommentTimeJan 18th 2011
     
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 19th 2011
     
    Posted By: CWattersPerhaps see also this thread..

    Thought we had discussed it before on here :bigsmile:
  14.  
    S.T.- Surely the hazard is possibility of cable overheating beyond capability but I understand smallest cable used for lighting is 1 mil with 10A rating,I understand 1.5 often used mcb 5A therefore 50% of safe loading without further reduction .
    I have been in lofts where additional insulation has been installed by "professionals" under grant schemes but placed over cables which questions due care when heavy load ccts such as electric showers are considered plus cable heating increases voltage drop and surely loss in effective power .
    Rgds
    Brian
    •  
      CommentAuthorSteamyTea
    • CommentTimeJan 19th 2011
     
    Brian
    It is the whole circuit and the capacity of that circuit (diversity) not just the current carrying capacity of the wire.
    The 17th Edition of the IEE regs, a fantastic bed time read, has pages and pages on it. I use the simpler onsite guide, but even that had 6 installation type, fixing distances for different cables and a couple of sections on external influences such as heat, water, dust and dirt ingression and impact.
    Trouble with most things is that the more you look into it the harder it gets.
    There is also an issue with some PVC cables and polystyrene insulation reacting. So it is best not to pour expanded posturing beads between the rafters without first checking the wiring type.
    • CommentAuthorCWatters
    • CommentTimeJan 27th 2011
     
    Apparently there is also a voucher offer at Focus DIY ..

    £8 for 4 rolls loft insulation until 31 Jan.

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