Secondary Double Glazing

[russ_fae_fyvie]

I know there is a recent thread on Magnetic Double Glazing but I wanted to ask for peoples thoughts on the system as a whole.

As you may know, we moved into our house last year and as with any new build, have been fixing the 'snags' as we go along.

The first big fix was to get all the massive external gaps closed in the soffits (an original design error by the house supplier) and now that they are fixed we no longer have the draughts we had before.

However now that they have gone, we are finding that the Double Glazed windows supplied with the houses, are, quite frankly, rubbish.

Not only are the smaller windows difficult to seal, I feel that the gap in the glass is far too small to make the double glazing any use.

This is especially the case on the large front windows which amount to approx 26m^2 of glass total.

The amount of cold air coming off them is ridiculous and hence the reason for looking at Secondary Double Glazing.

I think the frames are perfect to a pane of Plastic to cover the whole glass area in each window (check the photo) but I would like recommendations for the type and thickness of plastic that would make a difference. I would intend to leave the 2nd and 3rd level Secondary glazing in all year round (mainly due to access) but the lower ones can be removed in the summer.

I know there are different grades of plastic you can use but which is the best for longevity and practicality.

As you can see from the photos, there is plenty of scope for fixing as well.

[dhaslam]

Have you priced replacing the window glass  with triple glazed units or perhaps just doing the important sections with secondary glazing on the others?

[Bodidly]

Hi

I have made some scientific equipment from 4mm high cast acrylic this was used outside in the south of France for a few summers. After this time it was slightly cloudy and had become a bit brittle also I seem to remember the 2.4m x 1.2m sheets costing nearly £70 each. Why not just use glass for the secondary glazing?

Beau

[russ_fae_fyvie]

Can't really afford a proper solution for a couple of years while we recover financially from the actual build. Thats why I thought if this would work for 2 or 3 years it would help keep the house warm and then when we have some dosh we can look at a proper solution, like replacement.

I also thought of glass instead of plastic but because of the size of the windows I think the weight for DIY would be dodgy. Having said that I have asked a local Glazing comepany tro quote me for them to install galss secondary glazing, however like most Glazing companies, I'm still waiting for them to call back !

[Bodidly]

The high cast acrylic is easy to cut and outside in the south of France is quite extreme so could be OK. Good luck with the glazing quotes. I could send you a sample as the last job I did for this firm got cancelled so I have 120 250mmx250mm squares in the workshop.

Beau

[russ_fae_fyvie]

Thanks for that, I am just waiting to hear back from a coupled of secondary glazing (plastic) suppliers so once they come back to me about what they have I may take you up on the offer.

thanks again

[johnrae]

Adding another layer to create triple glazing is a feasible option but there is a "but", as I've found in practice.

If you fit the (let's call it plastic)  glazing to the inside of the building and you do not have a perfect hermetic seal between the plastic and the existing double glazing ( the realistic situation) you will get condensation between the sheets as the warm interior air meest the relatively cool glass surface.

However, if you fit the plastic to the exterior of the building, with an imperfect seal, the air outside the plastic is at the same RH as the air in the gap so condensation will not occur.   The fact that you are preventing >99% of the wind from hitting your glass, the thermal efficiency of your existing glazing will increase enormously. 

[Billy]

What johnrae says does make sense but it's not always easy to fix floppy plastic on the outside where the wind can suck it out.  You could make it stiffer by introducing a gentle curve but a lot of work.

The gap between the window and the secondary panes should not be too big otherwise you get enough space to allow warm air to rise and cold air to fall in a big way.  25 mm is about the max, any more and it's a big chimney and you ideally want the air to be still.  I use 3mm acrylic and take them down in the spring, but work they do.  Big double glazed units with a small gap can suffer from the cold reducing the volume of gas in the panel and bringing the panes rather too close together.  Expensive units can have a bladder to compensate and smaller units will blow seals if using thick toughened glass that won't give.

I know what it's like sitting under a large area of glass like that.  A veritable waterfall of freezing air.     

I hope you get a solution 'cause the house looks brill.

billy
 

[billi]

500 Euro      does not look brilliant  but helped a lot  





Seriously  on the long run  , perhaps a single glassed (nicely designed  )  conservatory  would be not much more expensive than triple glazing  that whole house side  you have


Just a thought ....

[Baz]

Fantastic building but do you need all of the windows all of the year? how about sealing some of them off with 2 in celotex for a few months or outside wooden shutters or very heavy curtains. A blanket stretched and held against the frame with those spring curtain wires would stop a lot of downdraught but breath to reduce condensation and suitably decorated could be a stylish feature.

[HalcyonRichard]

Hi,
    About 20 years ago when I was "broke" with little money and single glazing I used the double sided tape and a special film. It is cheap and not too obtrusive. It made a big difference but is not suitable for long term use. See :-

http://www.diy.com/nav/build/insulation/draught-excluders/seals/Stormguard-Secondary-Glazing-Film-10908059

It's £ 7.99 for a sheet 4m x 1.5m. So it's not expensive to try it out on a couple of windows.

You put double sided tape around a window then stick the film on. You then use a hairdryer to"shrink" the film until it's as tight as a drum. I finally had standard double glazing fitted. This was a very good stop gap until I got back on my feet.

Regards Richard

[JohnS]

I can second Richard's recommendation of the DIY sheet solution.  You can use a hot airgun instead of a hair dryer, but hold it a bit further away.

John

[skyewright]

Seriously  on the long run  , perhaps a single glassed (nicely designed  )  conservatory  would be not much more expensive than triple glazing  that whole house side  you have

Just a thought ....

My thought too, but given comments above probably one for Russ to think about in a few years time?

In the meantime "cling film" style secondary glazing or "winter only" opaque insulation seem like good ideas.

If biff pops in here he'll probably suggest L2L (i.e. foil faced bubblewrap). Another brand of the same thing is YBS Airtec Double.

Actually, just bubble wrap on its own is another (very temporary?) possibility. I've seen it spread over a window, just held there by static &/or suction (just like a tax disc holder).

[Baz]

When you think about it Planners should be stomping on this sort of design now. Big windows are ok for the solar gain of course but winter shutters should become mandatory above a certain % of glass in a room.

[Billy]

At least specify triple glazed stuff like the Swedes, no thermal bridging and shutters, yes please.  It can be done but the UK has a long, long way to go yet.

billy