Glazing tape - Double Glazing vs Linseed paint

[AMc]

I know this has been discussed before but I'm about to order about £8000 of double glazed units for my vinery and other windows. The joinery has been painted with a linseed based paint from Beckers. I really don't want to get this wrong

What is the best way to keep the seals physically out of contact from the frame - I've read about glazing tape, but before I buy hundreds of metres of it I want to make sure I'm getting the right stuff for the job. The glaziers gave me a blank look when I asked them about the best course to avoid problems, but they're sulking because I'm not paying them to fit the glass.

I'm shamelessly touting for biffvernon's advice but all informed opinion is welcome!

 

[Andrew Bodenham]

I used to use butyl rubber putty to bed in d.g. units, until I experimented with glazing tapes. Now I use EDPM tape exclusively, and so far (4 years) I have not had any problems or customer complaints. Certainly from an installation point of view the tape is far quicker to use than putty or other 'goo', and in my opinion provides a much more reliable engineering solution to achieving a seal that can accomodate the various thermal / humidity movements that occur in timber frames. Of course, you need to ensure that other weatherproofing details are correct too, such as sufficient run-off angle on beads, and beads correctly set at the corners. I have also experimented with re-designing frames so that the beads are internally applied as a way of reducing the number of fallible components exposed to the weather. Even simple things like specifying non-ferrous pins in beads can make a big difference to the service life of a window and d.g. units. Truly God is in the details.

Reddiseals.com have a good range of tapes.

 

[AMc]

Non ferrous pins aren't something I would have thought of.
Thanks - that's just the kind of specifics I'm after!

 

[biffvernon]

I agree with Andrew. I use this: http://www.ukindustrialtapes.co.uk/tradecounter/Glazing-Products/shopexd.asp?id=2382
Note that it's over £8 per 25m roll but only £3.50 if you buy a box of 25.
I've always had very prompt and helpful service from this firm.
I use the brass panel pins from Screwfix. 25mm is probably the most useful size.

 

[AMc]

Excellent tips thank you very much

 

[Me!]

I am also about to double glaze a window for the first time in years, and having only used butyl rubber before I was interested to hear about tape but not sure how to use it. If anybody else is interested, Google turned up these instructions with contributions from a familiar name.

 

[biffvernon]

Gosh, there's one from the archives!

 

[AMc]

Having read through the DIYnot thread - it looks like I also need blocks to support the units but I'm having no luck searching without knowing the 'proper name' for them. Any suggestions/recommendations would be appreciated.

I assume I also need to buy the right thickness of tape to suit the rebates and double glazing units - is there a formula i.e. unit width + glazing tape thickness - compression?

Finally I will be attaching some plant on bars - again a tape recommendation and any hints would be very welcome.

I'm getting equally excited about having my house weathertight/scared about trashing my expensive joinery or units

 

[biffvernon]

The blocks are more important with plastic windows. Any water that gets in will just sit there in a puddle and the blocks keep the unit up and dry (that's the theory). With wooden windows, if not painted in the rebate, if water got through it would soak into the wood and eventually dry out through the exterior (especially if not painted or a seriously breathable paint is used), rahter than forming puddles so the blocks are not so important.

When I need to have a spacer I use the little squares of cork that my glass supplier uses to separate sheets of glass in a stack.

I mostly use 12mm x 3mm tape. But I don't do plant on

 

[AMc]

But I don't do plant on

My choice in places were 4 tiny units with massive glazing bars or plant on with spacers in the unit. Given I couldn't tell the difference between plant on with spacers and the multi unit sashes I have (massive glazing bars aside) it seemed like the lesser of two evils.

I couldn't have done plant on front and back with no spacer - that just looks weird with a 24mm unit!

 

[biffvernon]

They may look all right but you will know they are fake.
:wink:

 

[Andrew Bodenham]

They may look all right but you will know they are fake.

It's a better technical solution than using individual glazing units, it'll look as good as a d.g. window can look, it allows the use of a nice, narrow (fake) glazing bar. I don't think AMc needs to lose much sleep over the "fakeness" or otherwise of his new windows.

Amc:
Ironmongerydirect.com have a good range of glazing tapes, bar mounting tapes, spacers etc. in their catalogue. Also see Reddiseal.com. Any inert material can be used as spacer blocks.

In the past I have used the 'E' section EDPM tape, but I think that the 'lipped' profile would give a better weatherproof finish, although marginally more visible. Double sided tapes are available, but I think that they would not allow much margin for error during assembly!

 

[AMc]

And I thought this was going to be simple

I'm not going to lose sleep over my 'fake' bars - they're the best compromise I can come up with until someone works out a glazing system that's 4mm deep and has a U value under 0.5W/m2.

This scale image made in Google Sketchup shows how the vinery would look if I contructed it with real 50mm glazing bars at the same centres as the Victorian one...more wood than glass.

Even with 'fake' 20mm bars it looked like a prison cell inside when I mocked it up on the computer.

The design moved on a bit and we've halved the number of vertical bars in the main screen and simplified the gable (not shown). The rafters and window spacings are the same but you can actually see out of the windows which wasn't possible when the structure was first built ... and wasn't a priority when it was used to grow grapes.

I've very grateful for your advice.

 

[biffvernon]

50mm glazing bars? Ah. I aim for around 32mm. Kind of Queen Anne-ish.