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    • CommentAuthornigelm
    • CommentTimeOct 18th 2017
     
    Due to cost constrints it looks like i am going to have to make my own double glazed windows.

    I will be using timber for the frames and one sliding door is big. This would normally need quiet big timber sections.

    Having installed some upvc frames, it was evident that most of the strength comes from packing the glass tightly into the frames.

    Would it be feasable to use finer timber sections by using the glass as a structural membes similar to the upvc windows.

    I will be using sweet chestnut as that is locally available and is nice to work with.
    • CommentAuthorowlman
    • CommentTimeOct 18th 2017
     
    You may be opening up a can of worms, here's a it of technical stuff to help.

    http://www.cwct.co.uk/facets/pack08/text06.htm
    • CommentAuthortony
    • CommentTimeOct 18th 2017
     
    Yes, why not go for 3g it will be even stronger then.
  1.  
    Packing the glass tight into the frame doesn't add strength, it just helps stop the frame sagging (so easily) by helping to hold the frame square.

    If you follow this approach be aware that it is usual to have a gap between the bottom of the glass unit and the frame. This is done as it has been found that when the inevitable water/moisture collects at the bottom of the glass/frame this will not drain without a gap and eventually the water will go into the glass unit and cause misting.
    • CommentAuthortony
    • CommentTimeOct 18th 2017
     
    Ever seen European woof frame Passive Haus windows?
    •  
      CommentAuthordjh
    • CommentTimeOct 18th 2017
     
    Not sure what your point is, Tony? Which particular window design do you mean?
    • CommentAuthornigelm
    • CommentTimeOct 18th 2017 edited
     
    Taking the UPVC aproach the glazing would be packed tight at the corners holding the frame square. Using the correct plastic packers would give enough of a cushon to take up any expansion.

    The glazing bars would hold the frame against the glass prevemting twist.

    My thoughts at the moment are to make the frame section flimsy so that the frame will move with the glass rather than a ridgid frame potentially putting stress into the glass when tightly packed.

    We are in France and glazing is relativly expensive. However i have found tripple glazed units at an ok price. There is am option to use thicker / toughened glass on the outer panes if nececary.
    •  
      CommentAuthordjh
    • CommentTimeOct 18th 2017
     
    Posted By: nigelmWe are in France and glazing is relativly expensive.

    Is the price of East European windows different in France to the UK?
    • CommentAuthortony
    • CommentTimeOct 19th 2017
     
    Good idea the thicker toughened, mine is on the inside.

    Re glazing and packers, I have seen that in Europe the fully bond the glazing units into the frames using silicone and have been successfully doing this for over 50 years, silicone needs to compatible with glazed sealed unit seals
    • CommentAuthorBeau
    • CommentTimeOct 19th 2017 edited
     
    Built my windows and French doors with thicker sections and always regretted it.

    Glass adds so much stability to opening frames and dose not suffer seasonal movement. As far as I can see all the opening frame has to do is provide attachment points for hinges and catches and remain attached to the glass :bigsmile:

    Not sure about chestnut though. Never thought of it as very stable wood but maybe thats just through the drying process?

    Edit. I take the last bit back after a quick google "Sweet Chestnut is one of the most remarkable woods grown in Britain. The grain is similar in appearance to oak, perhaps a little less striking, but it is a much more stable timber. It splits easily, but as sweet chestnut dries it will tend to remain straight and develop very few cracks. It is just as durable as oak, has much less sapwood and is much easier to sustainably harvest as it grows quickly. It is not favoured by sawmills as logs can often have splits known as ring shake which renders some of the timber useless, but the fact is once any ring shake is cut out, it is for many purposes far superior to oak. Sweet chestnut is a little weaker and softer than oak, so not ideal for structural beams, but for is perfect for furniture, cladding, decking and increasingly window making (where it is superior to anything else grown outside the tropics) and boatbuilding. Do not confuse Sweet Chestnut with Horse Chestnut which is not related, and is a very poor wood with few uses." Guess it's pretty good!
    •  
      CommentAuthordjh
    • CommentTimeOct 19th 2017
     
    Posted By: tonyRe glazing and packers, I have seen that in Europe the fully bond the glazing units into the frames using silicone and have been successfully doing this for over 50 years, silicone needs to compatible with glazed sealed unit seals

    Indeed, but that still doesn't clarify what point you were trying to make?
    • CommentAuthortony
    • CommentTimeOct 19th 2017
     
    If that is done then wedges and packers are not needed and the Glass becomes structural, thinner sections can be use but they must be very well jointed at the corners and non UK ironmongery used.
    •  
      CommentAuthordjh
    • CommentTimeOct 19th 2017
     
    The packers hold the glass in the correct place whilst being bonded, and maybe share the load with the bonding, I don't know.
    • CommentAuthornigelm
    • CommentTimeOct 20th 2017
     
    Thinking of the construction :-

    Mortice and tennon at the corners.
    Epoxy resin adhesive with filler to prevent any voids where water can get in.
    Glass fully bonded with closed cell spray foam. Again the foam will fill the glazing rebate fully, nowhere for water to get in.
    Thermally broken by laminating timber - hard foam - timber with epoxy resin.

    This is the opposite of the drained and ventilated construction flavoured at the moment. But I hope that by using modern materials (spray foam and epoxy) this will work.

    I would also like to spray paint the windows. I have used linseed oil paint in the past for its breathable qualities. Is there a breathable paint that can be sprayed available? ( Looking for a satin finish).
  2.  
    The strength of a mortice and tenon at the corners is the strength of the sheer. It would be stronger with 2 mortice and tenons per joint.

    Do you have accurate machining facilities to do precision joints? A very little error at the corners will result in a skewed window that will never fit properly.

    Have you done the numbers (what are they, out of interest) to see if the timber-foam-timber lamination is worth the effort for the u value gain?
    • CommentAuthornigelm
    • CommentTimeOct 20th 2017
     
    I am just following the commercial manufacturers who employ the foam sandwich construction. The timber will be laminated anyway to form the sections.

    The mortice and tennon joints will be cut by hand, I don't feel accuracy will be an issue, the joints can be relatively loose anyway if using epoxy.

    Following the rationale that the glass is providing most of the strength and the wood is bonded to the glass I am thinking of maybe using simple mitre joints.

    Next step is to gather materials and make some test pieces to further develop the ideas.
    • CommentAuthorowlman
    • CommentTimeOct 20th 2017
     
    Are you considering fixed glazed panels, or opening sashes or casements, and if the latter what size timber section and openings sizes, are you proposing, you mention "fine" ?
    • CommentAuthornigelm
    • CommentTimeOct 20th 2017
     
    There is fixed glazing and opening Windows.
    The biggest single unit will be 1100 wide x 3000 tall.

    Section wise it will need to be 60mm wide just because the triple glazing is 40mm wide. Depth will be arround 50mm. I need to CAD the sections to get the exact size depending on seals etc.

    I can get some standard size small DG windows locally cheaply. The next step will be to get one of these windows and cut it up to add the thermal break and foam in the glazing. I will make the section as small as I can then the fun bit, destruction testing to see how it holds up. Then maybe a second window for weather resistants this winter.
    • CommentAuthortony
    • CommentTimeOct 20th 2017
     
    I can’t see mitre joints working, double halved mitre joints may be.
    • CommentAuthorowlman
    • CommentTimeOct 20th 2017
     
    Fixed frame glazing generally won't be a problem with smaller timber sections unless the opening casements are hinged on the glazed frame, rather than the frame side that is affixed to the wall.

    For opening casements (i.e.hinged), You first need to calculate the glass weight; 4mm annealed glass weighs 10Kg per M2 therefore a 1M2 3G sealed unit will weigh 30Kg+ a bit for the spacers. Using your example 1.1M x 3M = 3.3M2 x 10Kg =33Kg and that's for one sheet of 4mm glass multiply by 3 and that single 3G unit will weigh best part of 100Kg._ ( I hope you are not planning hanging that hinged on frames that lightweight ).

    As PiH suggested if the frame of casements doesn't have enough structural strength in itself you are totally relying on the adhesive and/or weather seals to counteract the tendency of the outer edge of the sealed units to "drop"
    What hardware do you intend to use on those narrow sections remember that if outward opening you'll loose at least 10mm of your 50mm front view of the casement frame into a rebate and possible some on the other side with a moulding.

    I can't speak for your foam/wood laminate as I've never used it, but your idea of using mitred corners is a terrible idea IMO, as is making poor mortice and tenons and then using epoxy to counter that initial bad workmanship.

    I may be wrong but it seems what you are planning is bonding a frame of wood like a mitred picture frame around expensive 3G glass units and then hoping the hinge side bond wont break/separate/give. I wouldn't lay money on it, and even if it only drops a few mm whilst the widow is closed it'll make opening them difficult and reclosing them a nightmare.
    • CommentAuthorRick_M
    • CommentTimeOct 21st 2017
     
    what is the 'hard foam' in your lamination? Would cork do the job? Also, how about wedged mortise and tenon joints, I noticed this is how my very old windows are made. They also have a dowel through the tenon. Finally, you mentioned spraying linseed oil paint, however as it's so easy and quick to apply (though slow drying) I'm not sure it would be that useful to be able to spray it.
    • CommentAuthornigelm
    • CommentTimeOct 21st 2017
     
    At the moment it is at the idea stage.

    As pointed out the hinge fixing points will need to be considered and will probably need a larger section at these points. However most of the glazing is fixed and the largest opening will be a sliding door.

    The foam sandwich will use XPS or similar if it proves strong enough. I am hoping that the load will be spread over a large area for this to work.

    Mortice joints will be easy to make, the epoxy will ensure that there are no voids for water ingress.
    • CommentAuthorRick_M
    • CommentTimeOct 21st 2017
     
    I saw having no frame has also previously been suggested on the forum if it's a fixed window, the idea being you can overlap the brick nib with the glazing unit which insulates better than a frame. Haven't read of anyone actually doing it though.
  3.  
    Posted By: Rick_Mwhat is the 'hard foam' in your lamination? Would cork do the job?


    When I looked at Nordan windows many years ago they used cork as a thermal break.
    •  
      CommentAuthordjh
    • CommentTimeOct 21st 2017
     
    Purenit is also used.
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