Windows - Single Glazing, Underfloor Heating & LBC

[worms]

Coming back to the original poster's windows, in an old cottage with small windows, it is surely quite common to have casements where the whole issue of glazing bars may not arise?

The carpentry in my windows is fairly agricultural - the wood for the casements being 2 x 2 inch set into 2 x 4 inch surrounds. I don't think there would be much difficulty in these handling dg glass.

In a case like this, I would have thought there is little reason not to move to DG.

 

[biffvernon]

Nowt wrong with agricultural carpentry for windows in the vernacular.

Heather, I guess Canadian conditions are pretty different to over here. One thing I'm not sure about is the durability of your oak. We generally regard European oak as significantly more durable than American - I wouldn't use the American oak that is imported here on external joinery. But not all American oaks are the same and yours may be just as good. It might be best to look for local advice before deciding to not paint or varnish.

Varnish is not as long lasting in strong sunlight as paint. It is the TiO2 pigment which is a good protection against UV.

 

[CHRIS]

[Edited: just found the other thread with exactly the advice I need - thanks muchly for this wonderful resource.]

That is really the reason I dropped by - researching what we should have done so I can fix it in the spring and do the right thing for the rest. I did "feed" the wood with warmed linseed oil, made a trip to London and came back to find that hubby had varnished the exterior with one light coat to protect it for the winter. I also paniced as I read that linseed oil promotes mold.

I am planning on using Tung oil indoors. I hope that is the right thing to do. We would like to see the exterior wood rather than painting it because the wood is spectacular, but the exterior has to stand up to -25/-30C in the winter and 40+C in the summer. Everyone varnishes around here, but democracy isn't always a good recommendation. I planned on several coats of warmed linseed oil on the exterior. Is that a terrible plan and is there a non-paint solution (I do understand that the pigment in paint helps to protect the wood from damaging).

Any advice to a newbie would be gratefully recieved.

Why not look at one of the OSMO exterior products, I know they sell it in the USA so maybe you could find a stockist North of the border.

I just found this http://www.osmocanada.com/

They use it a lot in Germany where they tend to get much colder winters than here so may be better for your climate.

 

[Penners]

It is the TiO2 pigment which is a good protection against UV.

Is that simply because of its reflectivity, or does the titanium dioxide have some other characteristic that helps with UV protection?

TiO2 is the white constituent of paint, I believe. Does that mean that coloured paints don't offer as much UV protection?

 

[biffvernon]

TiO2 is a good pigment because it is very opaque - the light, including UV, doesn't get through. That's why it's used in sunblock. Most coloured paint has a lot of TiO2 in it anyway - it forms an opaque background for the coloured pigments to do their stuff on top of.

 

[Penners]

OK, understood. Thanks, Biff.

 

[Flyfisher]

Regarding 18mm DG windows, unfortunately I can't find the 'glossy' with the pictures so I can't post them. But I still have the accompanying letter, dated, September 2006, which includes:

All windows are of hardwood timber construction to a period design in common use from around 1750 through to the early 20th century. Narrow 18mm glazing bars are used throughout matching the Georgian/Victorian periods. No 'stick on' glazing bars!
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We offer a range of glazing options suitable for modern or new build dwellings (complying with part L of the building regulations) and also for listed buildings. Our latest windows are now fitted with plain white insulated spacers between the glazing sealed units to improve appearance, reducing the visual impact of glazing spacers - an improvement requested by many conservation officers. The introduction of insulated spacers has reduced the U value to 1.6/1.7, well within the current & proposed 2008 part L building regs.

They don't seem to have a website but I found this page with a bit of info.

On a related tack, I believe it is quite common practice to paint such windows such that the paint overlaps the glass anyway. This can easily add another 8-10mm across an 18mm glazing bar giving a total effect of a 28mm bar. It does on our windows anyway.

 

[Penners]

I believe it is quite common practice to paint such windows such that the paint overlaps the glass anyway.

This is generally regarded as good practice, regardless of the window deisgn. It helps to ensure that the raindrops don't trickle in between the glass and the putty.

 

[biffvernon]

Thanks Flyfisher - but it seems the 18 mm bar is still proving elusive. Is it Old Manor Cottages Ltd? I've sent them an enquiry.

 

[Flyfisher]

Yes. It'll be interesting to learn more.

 

[middi]

I share Biff's concern on this very thin, through, glazing bar for DG glass units.

If I constructed a window casement incorporating an horizontal bar to accomodate two DG glass units, constructed with a minimum 10mm wide vacuum seal, there will be a 20mm unsightly obstruction to be covered PLUS the thickness of the through section of the horizontal glazing bar. It woulld be really interesting as to how they would get away with an 18mm glazing bar.

 

[Penners]

How are sealed DG units fixed into the frame? Do they still use sprigs hidden within the putty? If so, I should imagine that an 18mm glazing bar gives precious little "meat" to get your sprig into.

 

[Nemesis]

They use a special tape, putty contains linseed oil which shouldn't be allowed near the seals as it's bad for them.

It looks to me that those windows have the thin bars by having the DG units not very embedded in the wood.

 

[Penners]

linseed oil which shouldn't be allowed near the seals as it's bad for them.

I'm glad I asked - thanks.

 

[biffvernon]

I got this reply:

Thanks for your interest.

All our windows have 18/19mm glazing bars. Not stick on and replicate traditional Georgian/ Victorian windows.

so am none the wiser!

Yes, dg units are held in with double sided sticky taps, not putty.

 

[HeatherJ]

Thanks for the advice, particularly the Osmo suggestion Chris - I'm on the trail Biff - we have 'old growth oak', and it is visibly denser and more 'orderly' grain than that in a modern oak door we had fitted. A local carpenter told me that no-one who knew what they were doing would remove old oak as it wasn't possible to get wood of the same quality.

I have been looking from advice from nearer home, but not getting much sense. The This Old House forum (with debate) recommends the use of something called penetrol and turps instead of linseed oil and turps and then two coats of acrylic paint as apparently oil paint isn't what it used to be. :shock: http://www.oldhouseweb.com/newBB/topic-15125.shtml
It didn't sound right to me, but I will call one of the Osmo dealers on Monday and quiz them on products used in the area and why.

Thanks again - and apologuises for dropping in on a thread. Over and out!
Heather

 

[biffvernon]

No, don't use an acrylic paint. It's better to leave the timber bare - that way it can dry out easily and won't rot. The paint layer tends to trap moisture in the wood and does more harm than good - unless it is a real linseed oil paint - just oil and pigment - which is really 'breathable'. The modern so called 'micro-porous' paints still don't have the vapour permeability of linseed oil paint. I don't know if anyone makes it in North America. We get ours from a Swedish firm called Allback, and there are also a couple of German manufacturers.

 

[londonman]

Double glazed units will naturally have thicker glazing bars (which in my opinion do not look as nice).

Sorry to disagree but you can have windows with narrow glazing bars as long as you can get BC to agree to a 4mm-6mm-4mm double glazing unit. The only downside is tht you can see the metal spacers in the windows (if you are right on top of them) but from the outside and a reasonable distance away - the windows will look as per originals.

 

[biffvernon]

Hard to get the required U-value with a 6mm gap, even with krypton or xenon fill, and it does not alter the arguement of profile width of spacer.

 

[Flyfisher]

The only downside is tht you can see the metal spacers in the windows (if you are right on top of them)

I believe that's why the ones in question used a white spacer - makes it even less noticeable.

As for the U-value, it might not meet latest regs but it would surely be better than a single pane.