They generally have a run of duct tape around the rim which overlaps from the inner to the outer pane, I think that's covering a layer of "black gunge" which is covering the spacer bar ... never tried removing the duct tape.
Yes some friends in a conservation are with avictorian house had to pay a lot more for look alike frames for the orignal. I wonder if you could just dress the outside to look like the old frames and just fit normal ones? Brian
No, but I have lived with these dreadful windows on a number of houses. For evolutionary biologists they are wonderful, over a winter the condensation on them supports vast colonies of fungi which alter colour from virulent purple through snot green to bright yellow. Attacked with bleach the hardiest survivors start growing the second you turn your back.
As replacing the windows wasn't an option most occupants resorted to retrofitting closed cell foam draught proofing around the window/frame and fitting secondary glazing which was removed in summer. This kept the fungal growth to a minimum and stopped the draughts which are Crittal's trademark attribute.
I can't see adding a thermal break inside achieving much, it would leave a cold strip which would still attract condensation. Looking around the web using secondary glazing appears to be the method of choice for dealing with the things.
Had them in my parent's house. Other trick was rust and or expansion etc broke glass regularly. Which lead me to believe it was normal to have to replace several panes of glass every year.
Possibly but I'll pursue this route for a bit: As the galvanised steel is angle iron and the glass, and its seal, will occupy the rebate how should I deal with this thermal element.
Worse case is that the steel is 3mm thick with a 25mm rebate and 60mm is exposed on the inside. So on my largest window I have a structural opening of1550mm wide 1300 with a softwood frame exposed to 30mm and
60mm deep,
Wood surface area 0.1284m2 what's a U value for 60mm softwood?
0.3W/m2 degC
Steel surface area 0.467m2 but what U value as the path is largely a
3mm cross section, possibly 20W/m2 deg C
glass surface area 1.4196 U value 5.6W/m2 degC double glazed might halve it??
So currently, if the above assumptions are near, I seem to lose about
250W if I heat to 20C and it's OC outside and potentially fitting dg panes might reduce this by a third. Which may be a saving of 600W throughout the house.
DG only reduces heat flow through the glass, secondary glazing tackles frame loss too, which is major with Crittalls. Double secondary glazing would of course be better, since Crittalls are so grim thermally.
Crittalls aren't normally fitted into timber frames if that's what you mean.
In the 50's and 60's Crittall windows were always fitted directly to the brick opening, so your experience is indeed limited.
Crittall still exist and make modern thermally broken DG versions but they aren't cheap, and removing old crittall windows without damaging the surrounding brickwork is not easy.
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