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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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    • CommentTimeJul 8th 2020
    "Water-filled glass can ‘revolutionise building design’ and performance when used as part of a wider heating system."


    "The water-filled glass system involves connecting the water-filled window panels to a storage tank using pipes embedded in the walls, so fluid can circulate between the two. This system allows the ‘Water Houses’ to cool and reheat themselves, without needing an additional energy supply for most of the year.

    "When it is warm, the buildings stay cool as the water absorbs external and internal heat; this warm water is then circulated to the storage tank.

    "According to Loughborough University, the heat is stored in the tank and, if the temperature drops, it can be brought back to the walls to reheat the building using a monitoring system similar to central heating. Alternatively, the stored heat can be used for hot water supply."
    You can keep tropical fish in the windows. :)
    • CommentAuthortony
    • CommentTimeJul 9th 2020
    All sounds like nonsense to me
    • CommentAuthorMike1
    • CommentTimeJul 9th 2020
    Interesting, but I can't see it being cheaper than an interseasonal store linked to underfloor pipes.
    • CommentAuthorCWatters
    • CommentTimeJul 9th 2020
    Kinda assumes you have too much solar gain in winter. Otherwise why block/store it?
    • CommentTimeJul 9th 2020
    To me, it all sounds more plausible in a climate with a diurnal swing where it's hot during the day and cool at night.
    Makes a change from filling glazing units with expensive noble gases I suppose. Now why ever did we do that? Sure there was a reason....!

    Several of this forum have circulated water in pipes inside walls and roofs to store heat, but they made sure it was combined with suitable insulation.
    • CommentAuthorowlman
    • CommentTimeJul 10th 2020
    If you combined the water-filled panes with insulated external shutters and a close by reservoir, the window itself plus maybe the area directly below could be the radiator when the shutters are closed.
    My immediate first reaction upon reading this was to check the date to see if it was April 1st.

    (Childish of me I know, but I just couldn't resist it. :-) )
    • CommentAuthorowlman
    • CommentTimeJul 10th 2020
    Looking at the diagram it appears the water "screen" is separate/centralised from the two outer panes although I guess the whole lot is a sealed unit.
    • CommentTimeJul 10th 2020
    The cross-section image appears to show a triple-glazing panel with the water between the inner two panes. The whole thing reminds me a bit of the solar-powered bubble-filled greenhouse construction.

    I wonder how this scheme compares against the transparent PV panel approach?
    • CommentAuthorMike1
    • CommentTimeJul 11th 2020 edited
    Posted By: WillInAberdeenMakes a change from filling glazing units with expensive noble gases I suppose. Now why ever did we do that? Sure there was a reason....!
    To slow down the convection of the gas between the panes of glass, which increases the overall thermal resistance of the glazing unit.

    Argon, and especially Krypton, are significantly heaver than air's nitrogen-oxygen mix, as per their atomic weights:

    Nitrogen - 14.007
    Oxygen - 15.999
    Argon - 39.95
    Krypton - 83.798

    Which is also why you wouldn't use Helium, even though it is a noble gas - it's atomic weight is only 4.
    • CommentAuthorEd Davies
    • CommentTimeJul 11th 2020
    WillInAberdeen was likely asking a rhetorical question, but it's the molecular weight that should be compared so nitrogen (N₂) would be approximately 28 and oxygen (O₂) would be ~32 reducing the contrast with the noble gasses.

    However, I've long been a little suspicious of the description based on viscosity resulting in slower convection. Looking at Wikipedia [¹] suggests that it's because monatomic gasses have lower specific heat capacities, because they don't have the rotation modes that polyatomic gasses have, and hence transfer less heat. Dunno.

    [¹] https://en.wikipedia.org/wiki/Insulated_glazing#Thermal_performance
    Mike, Ed, you want the Rayleigh number, which depends on the kinematic viscosity, which for semi ideal gases depends on the molecular weight. Heavier molecules -> more inertia -> more viscous -> less buoyant convection.

    Molar heat capacity is pretty much the same for all diatomic semi ideal gases 7/2R and slightly less for monatomic semiideal gases 5/2R.

    If instead you use water with a forced convection, there's way more heat transfer between the water and the room and the outside.

    The point of triple glazing is to have a temperature gradient from the room to the environment, so the fluid temperature should be inbetween the room and outside temperatures. But AIUI the proposal is to have warmed water circulating, so it will lose more heat to the outside, compared to triple glazing filled with with cool gas.

    All the heat is solar heat which would have ended up in the room otherwise. The water is presumably 'warm' rather than 'hot' so there's limited scope for storing it using the heat.

    The application seems to be for buildings which have excess solar heat, such as over glazed offices and supermarkets, who otherwise would be paying for air conditioning.
    • CommentAuthorMike1
    • CommentTimeJul 13th 2020
    Yes, in practical application there are a sure to be whole series of calculations involved involving the Rayleigh number, Nusselt number, and other obscure stuff too :)

    There's some free US software available from the Berkeley Lab that saves having to do the calcs (though probably not for water) at https://windows.lbl.gov/software/window
    • CommentAuthorbhommels
    • CommentTimeJul 14th 2020
    Posted By: WillInAberdeen
    The application seems to be for buildings which have excess solar heat, such as over glazed offices and supermarkets, who otherwise would be paying for air conditioning.

    This, to me, seems the driver behind the idea. Water has high absorption for IR radiation, better than low solar gain low E glass, so it will capture a large fraction of the incoming solar radiation as heat before it reaches the interior, which can then be taken elsewhere by pumping the water around.

    Perhaps a closed system with water and krypton would be nice: water fill for summer, krypton fill for winter. People like eco bling so there might be a market for it :devil:
    • CommentAuthorRex
    • CommentTimeJul 22nd 2020
    Some thug, trying to break-in will be in for a big surprise!
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