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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.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthordelprado
    • CommentTimeMar 11th 2018
     
    • CommentAuthorgoodevans
    • CommentTimeMar 11th 2018
     
    To gain what advantage over the grey stuff (by which I think you mean the foam with a split down it's length?
    • CommentAuthordelprado
    • CommentTimeMar 11th 2018
     
    Well, its much more insulative!
    • CommentAuthorjfb
    • CommentTimeMar 11th 2018
     
    Is it cheaper as well?
    • CommentAuthordelprado
    • CommentTimeMar 11th 2018
     
    no much more expensive
    • CommentAuthorjfb
    • CommentTimeMar 11th 2018
     
    Yes I guessed - so what is so rubbish about the grey stuff if you can just get same u value with thicker diameter for less
  1.  
    Delprado,

    The real problem in a domestic setting (AKA, A house) is that much of the pipe insulation is actually a bit of a waste of time.
    for sure, the Hot water tank must be WELL insulated, as should the boiler pipes to and from it, but outside of that, all the heat loss is inside the themal envelope, so all stays in the house anyway. It might not be in precisely the right place, but its still there.
    Trying to lag your DHW pipes to the sinks is also a bit marginal, as say, you run your kitchen sink. The hot water in the pipes will noe be stagnant for several hours until you wash up again. You aint going to keep it hot for those several hours, and the cost of doing so would not really be worth it.

    The stuff you are looking at is commercial stuff, where hte cost/benefit calculations are very different.
    • CommentAuthordelprado
    • CommentTimeMar 11th 2018
     
    Hi Dim, funnily enough I did have the same train of thought as you, but I figured it still makes sense to deliver the heat where it is needed, without loss, especially if you are using a trv on a rad and want room by room control?
    • CommentAuthordelprado
    • CommentTimeMar 11th 2018
     
    <blockquote><cite>Posted By: jfb</cite>Yes I guessed - so what is so rubbish about the grey stuff if you can just get same u value with thicker diameter for less</blockquote>

    Fair point I guess if its in a floor void where space doesnt matter, but it doesn't look very airtight to me (the grey stuff)
    • CommentAuthortony
    • CommentTimeMar 11th 2018
     
    Dimengineer +1 all the heat lost from pipes goes into the house
    Never could see the reason for insulating hot water pipes indoors, they will cool to house temperature as soon as water stops flowing so again all heat goes int the house.

    For sure insulate hot cylinders but not central heating pipes.
    •  
      CommentAuthordjh
    • CommentTimeMar 11th 2018
     
    Posted By: delpradoit doesn't look very airtight to me (the grey stuff)

    I guess its time to read the specs then, and see whether it actually is, rather than rely on the Mk 1 eyeball on photos.
  2.  
    Mice love to strip the 'grey stuff' and chew it up into heaps to nest in. I'm replacing the shreds that are left of our grey stuff, using pipe-shaped mineral wool which comes with a foil cladding which is self adhesive to seal it up tight.
    •  
      CommentAuthordjh
    • CommentTimeMar 11th 2018
     
    Posted By: WillInAberdeenMice love to strip the 'grey stuff' and chew it up into heaps to nest in.

    Ah, we don't have that problem. Mice are not allowed in the house.
  3.  
    That's what you think! :-)

    At some point in the lifetime of a straw house (or any other) there'll be mice.
    • CommentAuthorgyrogear
    • CommentTimeMar 12th 2018
     
    Posted By: djhMice are not allowed in the house.


    +1.

    However, we have five cats, and it is *they* that bring the mouses* in the hice !

    (generally very rough-looking, it must be stated)

    gg
    • CommentAuthorbhommels
    • CommentTimeMar 12th 2018
     
    I don't understand the argument for not insulating hot water pipes. When I turn on the hot tap, I don't want to heat my floor voids, I want hot water.
    And when I turn the hot tap off and on again a minute later, I want the water in the pipes to still be hot as not to waste the pipe lag again. So I have used the grey stuff everywhere, even the double thickness version where it fits. It does the job very well without costing much.
    • CommentAuthortony
    • CommentTimeMar 12th 2018
     
    I kind of agree but any heat in the pipe is going to escape into the house between uses, unless it is only a minute later.
    • CommentAuthorDarylP
    • CommentTimeMar 12th 2018
     
    a possible argument: in summer any extra heat input into the dwelling will not be beneficial; may lead to overheating, thus opening windows and 'losing' heat....?
    • CommentAuthorbarney
    • CommentTimeMar 12th 2018
     
    Typically, assuming say 50C for the HWS and say 20C for the ambient, then a good quality insulation would exhibit about 6W/m on 15mm copper pipe

    As important is not allowing the cold water service to "gain" heat from the ambient or from adjacent HWS pipes

    Personally speaking, I would always insulate both HWS and CWS with something like Kingspan Cooltherm closed cell foil faced insulation (best performance for thickness, to avoid "strange" pipe fixing details.

    Regards

    Barney
  4.  
    We’ve got a hot water circulation loop (house layout means the water tank couldn’t be central) and I insulated that with the grey split stuff as well as i could. Looked at other options and they seemed to be prohibitively expensive.

    I’m dubious about the benefits of doing much more, especially if you use plastic pipe.

    Hot water - if it’s used infrequently then the insulation doesn’t make that much difference - the water in the pipe still cools down. For 6 months of the year the lost heat is into the building so just substitutes for other space heating. the pipes tend to run in enclosed spaces (which probably contain insulation anyway) so you don’t get a lot of convection from them.

    Minimise the length of dead legs from the source, and use 10mm pipe for hot supplies to everything except the shower and bath. I didn’t for the kitchen sink - one of the things i’d Change if i did again.

    Likewise insulating cold pipes- other than for drinking you rarely want cold water. You normally mix it with hot to get a comfortable temprature so ambient pre-heating is not an issue.
    • CommentAuthortony
    • CommentTimeMar 12th 2018
     
    agree, it might be worth having a timer on the circulation pump, with it off most of the time
    • CommentAuthorbarney
    • CommentTimeMar 12th 2018
     
    Potable and non potable CWS applications are often combined in small installations and domestic properties - I hate cleaning my teeth in lukewarm water - I want it as cold as possible - so (wah shield up) I run the cold tap continuously whilst I'm brushing

    Once that "cold water" gets to around 20C, then all the things living in it start to proliferate - keep it as cold as possible is the best advice - hence it's a reasonable idea to insulate the CWS particulary if it's run in proximity to the HWS - which should also be insulated (in my opinion) - particularly if it has a circulating return

    Regards

    Barney
  5.  
    We got condensation on the cold water supply pipe where it enters the house, it comes up through a bathroom floor where air is warm and damp. Have insulated and sealed this section of pipe. Another section runs through unheated loft space, have insulated this against any risk of freezing.
    • CommentAuthortony
    • CommentTimeMar 12th 2018
     
    A cold water pipe inside a home will mostly sit at room temperature, insulated or not, if near a hot or heating pipe it could often be getting warmer than the house.

    There can’t be a problem with mains water doing this or lots of people would be ill every year for the last hundred years.

    Insulation does not stop heat moving through it, just slows it down. With plenty of time, hours, temperatures will equalise.
    • CommentAuthorbarney
    • CommentTimeMar 12th 2018
     
    It potentially will get to room temperature only if the flow (or demand) is very low - in normal use, the inlet water is circa 12C remember

    100 years ago we had poorly insulated and high air infiltration houses, much lower indoor temperatures, much less showering and not a great deal in the way of outlets dotted about

    I wouldn't dismiss the risk to the young, elderly or sick from water borne problems resulting from poor water hygiene practices and poor hydraulic design (dead legs serving infrequently used outlets for example)

    Do a few sums to estimate what the heat gain to a bare pipe compared to an insulated pipe really is over time

    Nothing to panic over, sure - but a bit of good practice goes a long way in keeping CWS temperatures down

    Regards

    Barney
    • CommentAuthortony
    • CommentTimeMar 12th 2018
     
    How long does water flow through a water pipe in a house? What proportion of time, only a few percent I reckon.

    It is impossible to keep water in water pipes that isn’t moving either cool or warm, it will get to room or house temperature within an hour or two.
  6.  
    Posted By: barneyIt potentially will get to room temperature only if the flow (or demand) is very low - in normal use, the inlet water is circa 12C remember

    100 years ago we had poorly insulated and high air infiltration houses, much lower indoor temperatures,


    100 years ago? My mother lived in a house without a bathroom into the late 60's in London - she was still using public baths. Our last house in Brixton only had a bathroom added with a GLC grant in the early 80's. But we've had the majority of people in the UK living in centrally heated houses for 50 years or more with no insulation on their water pipes and people are simply not getting sick from it.

    I'd guess most people's bathrooms don't get used between morning and evening so the legs to those are static for c12 hours. I've never heard of anyone flushing their pipes before drinking when they get back from a week away.
    I know that this is american but they recommend rotating your 'emergency supply' every 6 months.
    https://www.thoughtco.com/does-tap-water-go-bad-3975981
    • CommentAuthorgravelld
    • CommentTimeMar 12th 2018
     
    Another option is to consider reducing the copper coming from the cylinder if possible.

    Examples:

    - Use microbore
    - Consider using PEX
    - Consolidate wet rooms to the same area of the house
    - Consider not supplying infrequently used hot water in far flung parts of the house and use inline heating instead
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