Sun, 10 May 2026 03:32:20 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16205&Focus=275015#Comment_275015 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16205&Focus=275015#Comment_275015 Sat, 10 Aug 2019 04:07:21 +0100 gyrogear
To prevent early breakages, would appreciate feedback for mitigating thermal stress...
Obviously cannot do much about glass edge condition or internal clearances inside frames, so I'm looking at "operational aspect".

https://www.pilkington.com/en-gb/uk/architects/glass-information/functions-of-glass/mechanicalfunctionsofglass/glass-and-thermal-stress

(Ideally, patio doors for this usage would be sold with polycarbonate i/o double glazing, but no doubt I'll get round to doing that change before too long...). The alternative was having them made up - more costly...

Did not dare to bother Pilk***gton with this:

'''Glass and Thermal Stress
''Thermal Stress is created when one area of a glass pane gets hotter than an adjacent area.  If the stress is too great then the glass will crack.  The stress level at which the glass will break is governed by several factors.  Toughened glass is very resilient and not prone to failing due to thermal stress.  Laminated glass and annealed glass behave in a similar way.  Thicker glasses are less tolerant.  (…).

Location of building: = estuarine (french channel coast) (= "windy at times"...)
Orientation: = south (180°)
Type of glass used including details of insulating glass units: = Dual patio doors (OAH= 2000 x OAW = 2400); low-cost non-habitable DG (Grade ''E'') (4/16/4, Low-E), Uw = 2.6. Black-composite warm edge spacers.
Size of building overhang if present = NONE
Size of mullion and transom caps if present = Approx. 40 mm...
Details of any internal or external blind/louvres = NONE
Details of any backup i.e where a panel makes up a level to a floor or ceiling behind the glass allowing hot air to be trapped and reflecting back at the glass. = Sectional UP & OVER garage door, 40 mm thick (XPS), with external black aluminium skin; located 15 cms behind the window.
Framing material including thermal breaks and frame colour. = WHITE aluminium, no thermal breaks.
Window size & if opening changes the incident sun angle. = Twin 200 x 120; sliding (no change of sun angle).
Details of internal heating system: = Purpose of installation is to create a year-round solar furnace (plenum between garage door and patio door). Temp. approx 35°C to 40°C (?)
Any other details like other buildings or trees casting a shadow onto the glass. = Limited shading of window (east side, early morning) (flush-mounted inside garage-door reveal) -- to be confirmed after fitting. During collection, garage door is raised by 2 cms and both patio-door leaves are opened by approx. 1 cm, for external air ingress (via large suction fan). Aim is to use garage as an extended plenum, for heating the crawlspace to around 25°C or more...

I have not paid much for the windows, but nonetheless I'd prefer not to break them too soon; technology demonstration is one thing, but I'd like a bit of amortization

thanks for reading,

gg]]>