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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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    •  
      CommentAuthorrichy
    • CommentTimeJul 25th 2007
     
    One for Biff really.

    Whats the minimum spacer for a 4mm k glass unit which is Argon filled. I need to stay with as slim a unit that will pass Building Regs.
    •  
      CommentAuthorSpike
    • CommentTimeJul 25th 2007
     
    6mm. Have a google for Fountainbridge glass in Edinburgh who make units slim enough to putty-in.
    •  
      CommentAuthorrichy
    • CommentTimeJul 26th 2007
     
    2nd opinion anyone?
  1.  
    Hi richy, is it for an extension? I believe you can have the window base case u-value requirement relaxed if you 'trade' the difference to another thermal element [floors walls or roof]. You may need to do the calcs to prove this, though a sensible building inspecter would probably not have a problem if you can demonstrate that you have made a significant u-value improvement elsewhere.
    •  
      CommentAuthorrichy
    • CommentTimeJul 26th 2007
     
    It's a barn conversion for a client and the main contractor has used multi foil (oh dear!) Harrogate are passing tri iso 10 now!

    I've fitted all the windows with the usual 'k' glass + 16mm air space, I want to fit slimmer units in my 48mm doors because going to a bigger section door profileof 63mm just seems wrong. I have 38mm rebates and could shoe horn 24mm units in there, but I like to add 2mm flexi strip either side and I hate stepped beads...... I'm pretty sure Biff Vernon mentioned something about going slimmer with an argon fill on the old forum, but can't find it. 4-6-4mm as mentioned above would be cool as I can stretch to say 4-12-4mm , but wheres the data to keep the inspector happy?
    • CommentAuthorbiffvernon
    • CommentTimeJul 28th 2007
     
    Best insulation with argon fill is around 16mm gap. It gets worse as you go narrower (and wider). For a narrow gap use krypton fill.
    • CommentAuthorTerry
    • CommentTimeJul 28th 2007
     
    We have finally managed to track down a local glazer who has not only heard of edge seals with a thermal break, but has actually used them. However he has been persuaded that argon fill is a waste of time due to leakage.
    As most on this forum seem to advocate argon fill, does anyone know of any studies/info I can show him to prove otherwise?
    •  
      CommentAuthorrichy
    • CommentTimeJul 29th 2007
     
    If he's saying the gas can escape from his units, doesn't that mean they can also suck in moist air causing condensation between the panes?

    My local supplier has to buy in the argon units at little profit to himself, so he is always trying to talk me out of buying them and trying to talk me into his air filled units as he profits on the glass and the manufacture.

    Maybe this guy is in a similar situation?
    • CommentAuthorTerry
    • CommentTimeJul 29th 2007
     
    Hi Richy
    He came highly recommended from friends as a straight talking and fair bloke and comes across as such in person.
    Most of the glaziers around here seem to think argon leaks out and is thus a waste of time, but his chief influence seems to be someone from the BSI which from a quick google search seem to be the people who have issed his kite mark.
    He seems adamant (reading between the lines)that it is a waste of time on the basis that he doesnt want comebacks which will detract from his good reputation.
    High performance glazing is very new in our area as far as local suppliers are concerned and those I have spoken to dont understand the need for anything beyond K-glass.
    • CommentAuthorbiffvernon
    • CommentTimeJul 29th 2007
     
    It's hard to see how you are going to meet Part L without argon fill.
    • CommentAuthorMike George
    • CommentTimeJul 29th 2007 edited
     
    For existing dwellings and extensions: http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADL1B_2006.pdf
    Paragraphs 18, 19 and 20

    and for new build:http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADL1A_2006.pdf
    Table 2 [page 19]

    Note the limiting u-value of 3.3W/m2K
    • CommentAuthorTerry
    • CommentTimeJul 29th 2007
     
    to paraphrase most of our local glaziers
    'K-glass units give u-values around 1.7 - this meets building regs so why would you want anything lower'

    I think the 1.7 is from pilkingtons literature.
    In the same paper work they give 1.3 for Optitherm with air fill. Presumably this would be centre pane values.

    Do I recall somebody on here mentioning a web download for calculating whole unit U-values for windows ???
    • CommentAuthorMike George
    • CommentTimeJul 29th 2007 edited
     
    To put some figures on options[calculated via software]:

    4/6/4mm [k glass/air/float] will give you a u-value of around 2.1W/m2K. Substituting argon for air will bring it down to around 1.6W/m2K - Not bad at all.
  2.  
    Sorry Terry, we cross posted. The software I have used in the past is Tas [not free unfortunately]
    • CommentAuthorbiffvernon
    • CommentTimeJul 29th 2007
     
    Posted By: Mike George4/6/4mm.


    I doubt it. Should that be 4/16/4mm?
    • CommentAuthorMike George
    • CommentTimeJul 29th 2007 edited
     
    No, That is what it is according to the software. Do you know of any other software which calculates window u-values?
    • CommentAuthorbiffvernon
    • CommentTimeJul 29th 2007
     
    I don't know anything about software, but I do sell double glazing for a living, and if a 4/6/4 igu with Pilk K and argon fill has a centre pane U of 1.6 then I, and many others, are sadly mistaken. That is about the figure I would quote for a unit with a 16mm gap, but not with 6mm.
    • CommentAuthorMike George
    • CommentTimeJul 29th 2007 edited
     
    Okay, I may be wrong, the u-value does seem rather optimistic doesn't it. Software is only as good as the database and input values, and that is before you consider whether the alogrithm is calculating as you would expect.

    I have googled a free sofware for window u-values and will do a comparison
  3.  
    <blockquote><cite>Posted By: biffvernon</cite>That is about the figure I would quote for a unit with a 16mm gap, but not with 6mm.</blockquote>

    Yes, my mistake. Here is a pilkington brochure which gives their calculated values http://www.pilkington.com/resources/brpartlglassandbuildingregulations.pdf

    [Table 2 page 4]

    I would still like to know of software which calculates window u-values. The download I tried from buildesk does not. Anyone?
    • CommentAuthorMarkH
    • CommentTimeJul 30th 2007
     
    I too have heard that argon leaks from the units, although at a very slow rate. As for meeting a low u value without argon, would air filled tripple glazing be suitable?
    •  
      CommentAuthorfostertom
    • CommentTimeJul 31st 2007 edited
     
    Posted By: richyIf he's saying the gas can escape from his units, doesn't that mean they can also suck in moist air causing condensation between the panes?
    Not necessarily - different gases diffuse at vastly different rates. I've understood that Argon diffuses much faster than the other gases that make up air (78% Nitrogen, 21% Oxygen, 1% Argon, 0.033% CO2); however having had my first look at the Periodic Table in decades, I see that Argon (40) has a much larger molecular weight than Nitrogen (14) and Oxygen (16), so what's happening here - anyone explain? Also Nitrogen, Oxygen and air's conductivity (0.024W/mK) compares with Argon's (0.01772) and Krypton's (0.00943).

    BTW, do we realise how little CO2 there is up there, considering all the fuss?!
    • CommentAuthorbiffvernon
    • CommentTimeJul 31st 2007
     
    I don't think molecular weight has much to do with diffusion through a membrane rate. If you fill a party balloon with CO2 it goes down much quicker than when filled with air.

    There is also little connection between the quantity of something and how much damage it can do. A few micrograms of botulin on your dinner, Sir, or picogrames of Polonium?
    •  
      CommentAuthorfostertom
    • CommentTimeJul 31st 2007
     
    FRAME 4.0 was the whole-window software used by manufacturer Hajom Fonster as supplied by Swedish Window Co (both now sadly defunct) in 2001. These tables http://i30.photobucket.com/albums/c301/fostertom/hajomcalcs.jpg, http://i30.photobucket.com/albums/c301/fostertom/hajomcalcs001.jpg make interesting reading.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 31st 2007
     
    So Biff, do we know what it is about a particular molecule that makes it diffuse faster or slower, other than empirical testing? As well as DG fill, we'll need to know this so we can get a bit more scientific about the rate at which different molecules, pollutants etc diffuse in and out of breathing wall constructions. A breathing wall's not so healthy if it readily diffuses O2, N, CO2, H2O etc. but leaves carcinogenic cooking fumes trapped inside. I live in hope that selectively diffusive membranes can be designed that will do an extra-good job of diffusing pollutants out, so that we can live with lower airchange rates.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 31st 2007 edited
     
    If oxygen presently comprises 21% of air (the figure was higher in older, more energised human times), here's this, from http://mistupid.com/chemistry/aircomp.htm:

    "The air that leaves a person's lungs during exhalation contains 14% oxygen and 4.4% carbon dioxide.
    Atmospheres with oxygen concentrations below 19.5 percent can have adverse physiological effects, and atmospheres with less than 16 percent oxygen can become life threatening."

    So, as, apart from marine fauna, most of our oxygen is produced by tropical rainforests (which split that 4.4% CO2, so as to make that 14% O2 back up to 21%), of which an area the size of America still exists, and is being burnt at the rate of one Florida per year, let's hope that ............ well, let's just hope!
    • CommentAuthorbiffvernon
    • CommentTimeJul 31st 2007 edited
     
    I don't think you need worry about human breath, even from 6 billion of them, altering the atmospheric composition. We're rather small.

    It's marine flora, not fauna, that do the photosynthesising, and it's not just the tropical rainforests. There are temperate forests and even your houseplants that have their contribution to make.

    No matter how 'breathing' your wall is, the smell of your chip pan will go out the window much quicker than through the wall.

    I don't know much about what controls diffusion rates.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 1st 2007
     
    Flora, not fauna, yes. I did read that the tropical forests put the temperate ones into the shade (!) in photosynthetic significance. A tropical giant has 14 acres of leaf surface, against 4 acres on a full-size temperate and the solar radiation there is several times stronger. And the sheer wall-to-wall size of the tropical forests compared to the scattered gappy temperate forests. The point is, the 4.4% CO2/14% O2 exhaust of a typical fuelburner, whether human or industrial, has to be restored to 21% O2, and all animal life is solely reliant on the plants to harness solar energy to split that CO2 back into carbon and oxygen.
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