Magnetic double glazing

[stannn]

When I moved into my Derbyshire cottage in 1972, I had new window frames made by a local joiner from pitch pine beams which were from a factory demolition. That was a good move because they were like silk to the touch and still show no rot. They are coated inside and out with brown Sikkens HLS which is easy to apply and does not peel off with time. Sikkens is also very quick and easy to re-coat.
I later fitted secondary double glazing, of the flexible extruded channel type, with turnbuckles and glass. It is effective and glass is tough when it comes to cleaning but it is heavy to move and it would win no beauty contests.
I have found a dealer on ebay who sells brown magnetic glazing strip on a roll. Can anyone advise on the best type of plastic glazing material eg perspex to use when considering long term transparency and resistance to scratching during cleaning? I would think that deterioration in transparency would be less on the north side where it is not directly exposed to sunlight.

[A.L.]

hello stannn

glass absorbs the damaging U.V. wavelengths, so there will be little degradation regardless of orientation, the cheaper plastics are pretty similar with regard to scratch resistance.

[Ted]

I recently installed the mag strip type of secondary glazing on our front door - which has leaded stained glass in and around it. I used clear polystyrene sheets available from B&Q and these already had had some minor scratch marks on just from being transported/stored in the shop, despite the fact that it was fitted with a protective clear film on both sides. You may be luckier with other suppliers.

I don't think you can get any plastic sheets that are particularly resistant to scratching.  

[Baz]

Magnetic? neither of you mention anything steel in your windows.
I think the common sheets are polycarbonate but there are lots of others, like styrene (perspex), acrylic, acetate etc. There are some bullet proof plastics too.

[Ted]

You don't need steel in the windows.

The mag stripe is in two parts and both have a self-adhesive backing. A steel tape that you cut and stick around the existing window frame and the magnetic part that you cut and stick around the edge of the plastic sheet which then holds the two parts together.

[mespilus]

like styrene (perspex),

Ahem,

http://en.wikipedia.org/wiki/Poly%28methyl_methacrylate%29


The chemistry police will now retire from the scene of the calumny.

[Baz]

Of course (-man with Material Science degree hides head in shame -) I made some in school but that was last century.

The mag strip has potential, I will look into that further. Could work on solid insulation too.

[mespilus]

Of course (-man with Material Science degree hides head in shame -) I made some in school but that was last century.

The ChPS (Chemical Prosecution Service),
acknowledge the contrition exhibited
and will press no charges,

as they too,

spent more years in the previous century, than this.

[skyewright]

The mag strip has potential, I will look into that further. Could work on solid insulation too.

You might like to take a look at a recent topic on DIY secondary glazing over on the GreenBuildingForum too?

http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=6744

[TwoHorsePower]

The cheaper perspex stuff sold in the likes of B&Q is acrylic. Whilst more easily broken, acrylic is less easily scratched than the more expensive polycarbonate sheet. Acrylic is very easy to shatter if it gets a sharp knock or if care is not taken when drilling.

Polycarbonate sheet comes in many flavours/brands such as lexane and is very tough stuff indeed. It's used in the likes of motorcycle helmet visors and the triple wall plastic glazing panels, is more expensive than acrylic, and scratches more easily than acrylic. Some bikers use a stick on clear film to improve fog and scratch resistance. Experimental cyclists who build their own recumbent bikes/trikes sometimes use lexane/polycarb to 'blow' an aerodynamic canopy/fairing for their contraptions!

Flexible solar panels are covered in a clear film called ECTFE which is tough, scratch resistant, very transparent, etc. A few of us were thinking of looking at this stuff as a way of waterproofing DIY PV panels made from soldering together 'seconds' PV cells, so if anyone knows where to get ECTFE cheaply please post details here!

Cheap bodge: On some of our windows I use the flexible film which  one shrinks tight with a hairdryer. This is as cheap as chips (£2-3 worth does a room) and good for a temporary measure. The drawback with this stuff is that it is damaged easily and is a total write-off when it is removed. Furthermore, if not fitted carefully, it looks like you've put cling film over your windows! I have built a few simple wooden frames from roofing lath and fitted the flexible stuff to these frames. With a bit of draft excluder on the back of the frame, the removable frame can then be screwed to the fixed window frame and taken off in summer. Great at keeping condensation and drafts at bay.

Hope this helps

2HP

  

[Ivan]

Can someone point me to a supplier of the magnetic strips. I want to get the Navitron office windows secondary-glazed. They are metal-framed, so it could be even simpler. Is it possible to get a decent gap between the sheets of glass? 6mm is rubbish, but if it were possible to get 16mm, then we'd have reasonable performance.

Any condensation issues?

[Ted]

I bought a 15m roll off ebay for £15.  It's only suitable for use with plastic sheets. The gap you get will depend on the existing window frame profile although you might be able to build this up (certainly for a timber frame, not so easy with metal).

It has cut condensation completely for us.

[solar_cambridge]

Done some work for a chap who owns a large house of the victorian era. All 22 windows are sash. They were draughty so they looked at modern replacements which I think were quoted around £33k from a national firm. Instead, they got them refurbished which involved removing each window and routing a groove in each pane and installing a brush strip. For that they were charged 11k. I thought that was a lot to pay and the fitters(joiners) couple of guys were there for 6 full days I think. If you took out £500 for the materials thats would be generous and they didn't paint the windows which are flaking anyway.

The windows still have gaps around the brush strips and the windows are still obviously single glazed. 11k would have bought many years worth of shrink type film and they could have had all the windows stripped and repainted for a couple of 1000 I think with scaffolding.

[stannn]

Thanks to all who have replied.
Skyewright's link to the green building forum included comments from Mr Magicfingers about my main concern. He said that some of his acrylic sheets had bowed causing the magnetic strips to come adrift. This system is only as good as the quality of the magnet and of the adhesive. There does seem to be a variation in the quality available. Did he fit very thin acrylic to a large window? Was air pressure from a leaky windowframe the problem?
Ivan's project on a steel window removes the risk of bonding failure but still needs turnbuckles at the top for safety.
Ted, what is the thickness and unsupported area of your panel(s)?
Is it inevitable that a linear magnet like this will deteriorate over time because it is impossible to fit a steel keep such as you would see on a horseshoe magnet?
Stan

[Ted]

I did one bedroom window as well as the front door at that is 1400 x 1250 in one sheet. The largest piece on the door is 700 x 800. The polystyrene sheets were nominally 2mm thick but measuring them they are more like 1.6mm.