Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



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.

Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthorMike George
    • CommentTimeAug 1st 2015 edited
     
    Posted By: fostertomLike poythene then - not rocket science. Like polythene, all depends on the joint-taping.


    It certainly looks like polythene to me .... coated in something shiny - not sure what.. Rub it between your finger and thumb and the coating will come off.

    No comments on the air infiltration values?
    •  
      CommentAuthorfostertom
    • CommentTimeAug 1st 2015
     
    Just that 6000 is so high as to make no difference if it's actually found to be +9000/-3000 - total sun-block!
    • CommentAuthorEd Davies
    • CommentTimeAug 1st 2015 edited
     
    Tom, I need to think about this for a while but have in mind a simple finite-element model of half a rectangular void and half the adjacent material wall.

    With small cells, can we ignore convection completely (though, perhaps, include conduction through the air or other gas)?

    Don't need to worry about the speed of light - that can be considered “instant” for these purposes I'm sure. The questions are:

    1) In the steady state, what proportion of the heat flow is due to conduction in the walls and what to radiation across the voids?

    2) If there's a heat pulse, how much are these proportions skewed by the delay to conduction as a result of heating up the walls?
    •  
      CommentAuthorfostertom
    • CommentTimeAug 1st 2015
     
    Posted By: Ed DaviesWith small cells, can we ignore convection completely (though, perhaps, include conduction through the air or other gas)?
    Yep
    Posted By: Ed DaviesDon't need to worry about the speed of light
    My little joke!
    Posted By: Ed Davies1) In the steady state, what proportion of the heat flow is due to conduction in the walls and what to radiation across the voids?
    Good
    Posted By: Ed Davies2) If there's a heat pulse, how much are these proportions skewed by the delay to conduction as a result of heating up the walls?
    Not exactly. Not the proportion, more like what is the absolute total of the radiant component that is transmitted and received, during the time it takes before the conductive component(s) even reach the other side - and is that absolute total enough to have reduced the temp differential to zero, or almost to zero, all by itself without contribution from the conductive waste-of-time.

    There is a bit more 'instinctive' thought to offer, on objections that I'm expecting around process 2) - hare and tortoise come to mind!
    • CommentAuthorBeau
    • CommentTimeAug 1st 2015 edited
     
    OK have had little measure of the Triiso super 9. There is a line of stitching every 650mm across the roll. Stitch holes are 10mm apart and from what I can make out the hole is approximately 0.75mm max. The thread is 0.07mm and there is two lines in each hole. I am not going to embarrass myself by messing up the maths so will leave that to others. Hope there is an attached picture showing the layers.

    4 The outer reinforced foil
    3 Light open wading
    2 Very thin foil
    1 Spongy membrane

    Make up is 43211211211234
      DSC04034.JPG
    •  
      CommentAuthordjh
    • CommentTimeAug 2nd 2015
     
    Is the labelling of the photo correct? It's just that 2 & 4 look like foil to me, rather than 1 & 4. I presume 'Very this foil' is very thin foil?
    • CommentAuthorBeau
    • CommentTimeAug 2nd 2015 edited
     
    Posted By: djhIs the labelling of the photo correct? It's just that 2 & 4 look like foil to me, rather than 1 & 4. I presume 'Very this foil' is very thin foil?


    Sorry no. Some dodgy typing when I needed some sleep

    Now corrected
    •  
      CommentAuthorfostertom
    • CommentTimeAug 2nd 2015
     
    Posted By: BeauThere is a line of stitching every 650mm across the roll
    Is that '650' correct? Not how I remember it - I seem to have thrown my samples of such things away. Anyway, it's 650 or whatever c/cs in both directions isn't it - a square grid?
    •  
      CommentAuthorfostertom
    • CommentTimeAug 2nd 2015 edited
     
    Ea hole = pi.d2/4 = 0.442mm2
    Less 2 x threads = 0.004mm2
    So ea hole open area = 0.438mm2
    Holes @ 10mm c/cs = 43.8mm2 per m run of stitching
    Lines of stitching @ 650c/cs in both direcxtions = 3.077 lines per m2
    Total open area = 3.077 x 43.8 = 134.8mm2 per m2
    Equiv to 13.1mm diam hole per m2.

    So, sorry not 70mm diam but 13mm.
    Is that significantly airtight? Even postulating reductions due to small-orifice, self-closing inner layers etc?
    • CommentAuthorEd Davies
    • CommentTimeAug 2nd 2015
     
    FWIW (ie, not much), if it's actually stitching rows and columns on 65 mm centres then I make the area equivalent to a hole 42 mm in diameter:

    >>> from math import pi, sqrt
    >>> r = 0.75e-3/2
    >>> holeArea = pi * r**2
    >>> holeArea
    4.4178646691106465e-07
    >>> colsPerMetre = 1000/65
    >>> rowsColsPerSqMetre = colsPerMetre * 2
    >>> holeCount = 100 * rowsColsPerSqMetre
    >>> totalArea = holeArea * holeCount
    >>> equivRadius = sqrt(totalArea/pi)
    >>> equivRadius * 2
    0.041602514716892185

    Still be interesting to know how this stuff sucks.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 2nd 2015
     
    Beau, can you do a bit of blow/suck (put your mouth to it) to see whether you can easily suck air thro the stitching holes?
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 2nd 2015
     
    Beau has fallen over (as the old joke goes) :bigsmile:
    • CommentAuthorBeau
    • CommentTimeAug 2nd 2015
     
    Posted By: fostertom
    Posted By: BeauThere is a line of stitching every 650mm across the roll
    Is that '650' correct? Not how I remember it - I seem to have thrown my samples of such things away. Anyway, it's 650 or whatever c/cs in both directions isn't it - a square grid?


    No not a square grid just one direction. Probably was along the length of the roll but the sample I have left is as short as it is wide.

    Did the suck as you suggested before and yes its not hard to suck air in from the face but I doubt that air is coming in from the others side more likely just draws air through the face layer and is entering from the sides. As I mentioned back a page the layer labeled 1 seems to partly seal around the stitching hole.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 2nd 2015
     
    OK stitching is just one direction - it really stitching @ 650c/cs, or 65c/cs or what?

    Could you somehow clamp a small square of it, which you mouth would fully cover, with line of stitching across middle of it? Then when you suck, with your mouth covering all the holes on the face you can see, the air can only have come right through from the other face of the composite, not come in sideways.

    All in the interest of Science!
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 2nd 2015 edited
     
    Tom
    You are just reminding me of loads of, what are now, unacceptable jokes and quips. :cool:

    The 70's were such innocent times.
  1.  
    Posted By: Beau2 Very thin foil

    No idea about Triiso, but IIRC the equivalent layers in the multifoil that I've seen (YBS SuperQuilt) were what I'd call mylar foil.
    • CommentAuthorBeau
    • CommentTimeAug 2nd 2015 edited
     
    Posted By: fostertomOK stitching is just one direction - it really stitching @ 650c/cs, or 65c/cs or what?

    Could you somehow clamp a small square of it, which you mouth would fully cover, with line of stitching across middle of it? Then when you suck, with your mouth covering all the holes on the face you can see, the air can only have come right through from the other face of the composite, not come in sideways.

    All in the interest of Science!


    650 mm centres for the lines of stitching Tom. Will mess about later with the foil when my wife is out. Don't really want to explain myself sucking at a piece of old multifoil :bigsmile:
    • CommentAuthormike7
    • CommentTimeAug 2nd 2015
     
    Posted By: Ed DaviesFWIW (ie, not much), if it's actually stitching rows and columns on 65 mm centres then I make the area equivalent to a hole 42 mm in diameter:

    >>> from math import pi, sqrt
    >>> r = 0.75e-3/2
    >>> holeArea = pi * r**2
    >>> holeArea
    4.4178646691106465e-07
    >>> colsPerMetre = 1000/65
    >>> rowsColsPerSqMetre = colsPerMetre * 2
    >>> holeCount = 100 * rowsColsPerSqMetre
    >>> totalArea = holeArea * holeCount
    >>> equivRadius = sqrt(totalArea/pi)
    >>> equivRadius * 2
    0.041602514716892185

    Still be interesting to know how this stuff sucks.


    Blimey, Ed! And to seventeen significant figures too!
    I prefer the sum this way:
    100 holes per 1m row, and 1000/65 rows per m gives 1530 holes per m2
    Plus another 1530 for the columns makes a total of 3060 holes per m2
    Diameter of single hole will be 0.75mm times the sq rt of 3060 (which is about 55) ie. 55x 0.75 = 41mm

    Or... with the spacing of 650mm rather than 65mm, divide that answer by the sq rt of 10 to get 13mm
    (I ate all the pi's)
  2.  
    what if the hole has a bit of thread going through it???
    •  
      CommentAuthorfostertom
    • CommentTimeAug 2nd 2015 edited
     
    We did that
    Posted By: fostertomLess 2 x threads = 0.004mm2
    at least I did, just so some bugger wouldn't say Aha, but ....

    Gd work Beau
  3.  
    ok, missed that :)
    • CommentAuthormike7
    • CommentTimeAug 2nd 2015
     
    If the thread dia is one tenth of the hole dia so two threads will take up about two hundredths of the area ie 1/50. The area left will be 49/50 of the original, so the 'equivalent' single hole dia will the 41mm times the sq rt of 49/50, which is 0.99 near enough, which is still 41mm given my level of approximation. With Ed's 17 figures it comes to 41.2mm, rounding off the last 14 figures! (I make it that 17 figures is sufficient to give the distance to the moon to an accuracy of hundredths of a micron). Anyway, messing up the neat hole with the threads will I suppose reduce the discharge coefficient - an experiment is needed!
  4.  
    I dont see how the thread is going to only take up one tenth of the hole area, I would calculate that the thread wil probably block at least 60 percent of the potential air leak.
    • CommentAuthorEd Davies
    • CommentTimeAug 2nd 2015
     
    Posted By: mike7Blimey, Ed! And to seventeen significant figures too!
    Well, yeah, could've added an extra line to round the result which nobody else (except maybe Steamy) would have understood so thought it better to leave it out and round it myself.

    Still don't believe the stitching is on 650 mm centres. That's like yay big; waving hands around rather than fingers.
  5.  
    Actis multifoil is welded, not stitched and their product certificate claims 100 percent air barrier.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 2nd 2015
     
    Posted By: bot de pailletheir product certificate claims 100 percent air barrier
    Of course - nothing special - like polythene - all depends on the jointing/detailing/tape, installation care and durability of same - that's where it falls down.

    Posted By: bot de pailleI dont see how the thread is going to only take up one tenth of the hole area, I would calculate that the thread wil probably block at least 60 percent of the potential air leak.
    Nah
    • CommentAuthormike7
    • CommentTimeAug 2nd 2015
     
    Posted By: bot de pailleI dont see how the thread is going to only take up one tenth of the hole area, I would calculate that the thread wil probably block at least 60 percent of the potential air leak.


    I was just using Beau's figure of 0.07mm for the thread. Have just been and measured some ordinary sewing thread (0.15mm) and button thread (0.25mm), both no doubt squashed a bit by the micrometer. Also some monofilament which was 0.25 mm, so Beau's figure looks suspiciously low - I wonder if it was 0.007in ? Suppose it is 0.25mm: That would be one third the dia of the needle hole, so one ninth the area. Times two for two threads and subtract leaves seven ninths. Sq rt of that is about 0.88 so equivalent dia would be 0.88 times 41.6 = about 36 mm, ignoring any change in the discharge coefficient.
    • CommentAuthorBeau
    • CommentTimeAug 2nd 2015
     
    Ed. Yes it's definitely 650mm between the lines of stitching.

    mike7. Yes I was surprised how thin the thread was and measured several times with slightly varying results but I stand by 0.07 mm

    OK now for the suck test.

    Not sure weather I have just done this just for your amusement or a genuine scientific experiment but I can say it is NOT airtight but taping the edges made big difference to speed of my possible suffocation. Interestingly I could not noticeably blow through it.
    •  
      CommentAuthorSteamyTea
    • CommentTimeAug 2nd 2015
     
    Posted By: BeauOK now for the suck test.

    Not sure weather I have just done this just for your amusement or a genuine scientific experiment but I can say it is NOT airtight but taping the edges made big difference to speed of my possible suffocation. Interestingly I could not noticeably blow through it.


    Smile, your on Candid Camera :bigsmile:
    • CommentAuthorBeau
    • CommentTimeAug 2nd 2015 edited
     
    Posted By: SteamyTea
    Posted By: BeauOK now for the suck test.

    Not sure weather I have just done this just for your amusement or a genuine scientific experiment but I can say it is NOT airtight but taping the edges made big difference to speed of my possible suffocation. Interestingly I could not noticeably blow through it.


    Smile, your on Candid Camerahttp:///newforum/extensions/Vanillacons/smilies/standard/bigsmile.gif" alt=":bigsmile:" title=":bigsmile:" >


    Na I checked the room before carrying out such lunacy.
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press