retro fitting double glazing

Does the seal come over the outer pane of glass as this is the only bit that would be slightly proud I think?

AJH

Frame conduction is the major problem with Crittalls. I would have thought you'd be better off with secondary dg.

NT

Your's is a good case for the Pilkington "vacuum" super thin panels - if you can find them, and if you can afford them...

It is probably worth doing a calculation on the loss through the DG units versus heatloss throughh the frame

I do know that they are bastards for frame condensation.

YOu can also get new crittall DG units

I would be inclined to ask them for details and a quote

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

Steel frames are bad news. Get rid of them.

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.

Not in my experience of these in the last 35 years Peter, perhaps you should visit and see?

These are galvanised so have not spalled and broken the glass, in fact the only pane I have replaced was one I broke with a football.

They are set in a 9" solid brick wall so the next thing on my list to cut thermal losses.

AJH

I've a feeling a modern putty that flexed would have helped - I'm talking about a long time ago.

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

Wood surface area 0.1284m2 what's a U value for 60mm softwood?

Steel surface area 0.467m2 but what U value as the path is largely a

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

It has never been a problem here.

AJH

If you want to be a lot clearer maybe we can get somewhere.

NT

Okay put more simply: the structural opening is 1550mm wide 1300 high and has an area of 2.015m2

The timber surround has 30mm exposed and is 60mm deep and thus has an area of 0.128m2

The steel area viewed from the inside is 0.47m2

The glass area is 1.42

I think I can only reduce loses by 30% with double glazing would secondary glazing do better?

AJH

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.

NT

On 14/10/2017 23:48, snipped-for-privacy@gmail.com wrote: ... snipped.

In my (limited) experience this isn't correct.

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.

Not always. I grew up in a house with them and tehre was a bit of wood there as well on some of them

Angle grinder.

Not always true in the 20s and 30s

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