Double glazed windows/glass

[gripen]

So having been to the first world countries and seeing how they live, I've come to realise that double glazed windows are the way to go. Does anyone know a specific reason why we don't have them here?? It's not like our winters are not cold - in *most* parts of the country. I've seen them here and there (like in the steam room at the gym) so someone is making them or bringing them in.

I'm prepared to go as far as replacing all the glass in my next house with the double glazed (or whatever it is actually called) variety for the comfort and temperature stability. Hopefully, heating will actually heat a decent area then and not the 2 cubic metres around the heater only...

So have you done this? What is the cost ratio i.e. how much more expensive is it? With zero knowledge, I would expect around 5x the cost per unit.

 

[Skywalker786]

So having been to the first world countries and seeing how they live, I've come to realise that double glazed windows are the way to go. Does anyone know a specific reason why we don't have them here?? It's not like our winters are not cold - in *most* parts of the country. I've seen them here and there (like in the steam room at the gym) so someone is making them or bringing them in.

I'm prepared to go as far as replacing all the glass in my next house with the double glazed (or whatever it is actually called) variety for the comfort and temperature stability. Hopefully, heating will actually heat a decent area then and not the 2 cubic metres around the heater only...

So have you done this? What is the cost ratio i.e. how much more expensive is it? With zero knowledge, I would expect around 5x the cost per unit.

I guess our winters are not as cold as the UK, and probably cost.

 

[maumau]

i absolutely agree with you about the double glazing and would love to install but it works out expensive. not only does it keep the warmth inside in winter but it keeps dust and noise out too ..... that's a huge bonus.

 

[chrisc]

I fitted "intruder-proof" glass. It has 2 layers separated by some sticky substance. It is 4.5mm thick on the windows and 6.5mm on the glass doors. Not only is is very strong (and fairly heavy) but also has excellent sound, uv and heat insulating properties. To test the heat, I put a 1500 watt panel heater next to the window and turned it up full. In 15 mins the glass on the inside was 38 deg but outside the glass was 19 deg (the outdoor temp was 14 deg)

Very well worthwhile. I have recommended it to several friends who have had it done and they are all very pleased.

 

[Timber_MG]

The biggest factor in insulation in SA houses is air exchanges per hour or how air-tight the house is. Our building standards and codes are very lax here in South Africa and thus windows alone are only part of the solution.

If you are really interrested, familiarize yourself with passive house design concepts as a good introduction of maintaining optimal in-doors climates. Thermal bridging, taking all aspects of the house's shell, from floors and foundations through roof into consideration and accounting for solar gain will give you a better understanding of how to maintain a comfortable in-doors climate (temperate both absolute and evenness throughout the house, humidity and dust/volatiles) with minimal energy input.

Well insulated houses don't only have lower heating/air conditioning costs but the more even distribution of heat (floor to roof for example) makes for a more pleasant environment.

Normal double glazing with plain aluminium frames have a very distinct disadvantage with much of the better insulation of the double window pane being undone by the large area high thermal conductivity window frame. Ideally one uses a thermal break type frame. Plastic frames work well thermally, but I'd not trust their UV-exposure life-times for SA conditions. Wooden frames have maintenance issues.

The most basic solution is to seal your windows properly and stop the biggest gaps.

Then identify the biggest thermal conductors between your interior and outside. Prime offenders are house corners (a so-called geometric thermal bridge), windows, exterior wall perimiter to surface soil, roof insulation, walls (and our double brick walls often don't have a sufficient air-space with mortar and/or steel briding the two thermally)

For my house I am considering making up frames from the extrusions on my CNC router and have a glazer fit the panes and seals (double E-glass if possible).

 

[Timber_MG]

The PVB layer between the panes is a feature of safety glass (it's stuck together in an autoclave and is similar to a car wind screen) that absorbs vibration very effectively, but insulation is just a factor of the thicker glass with double glazing having a significant advantage here.

Insulating windows is relative to how well insulated the rest of your house is. If your walls are well insulated and the windows are a weak link, then the aditional cost will be worth it. If your roof and floor leak heat like a sieve then single pane security glass will do.

 

[ponder]

I fitted "intruder-proof" glass.

That's probably just normal laminated glass being called "intruder-proof" in crime ridden SA making people feel better about the purchase.

Laminated glass is easy to break but hard to penetrate, laminated tempered glass would be the next step up from that but more expensive.

Laminated glass does not have the same insulation capabilities as double or triple glazing where the air gap in between provides the insulation similar to layering clothing in cold weather.

http://www.pgglass.co.za/ -->Solutions-->Building Glass Solutions-->Energy Efficient Solutions

 

[ice_cubes]

I wonder where the SouthernSun hotels buy their windows from, they are the best!

 

[gripen]

Irrespective of other factors - walls, ceiling etc - surely it would make some kind of difference replacing the glass? Nobody has said anything about cost yet. I'm wondering what this (http://www.pgglass.co.za/index.php?option=com_content&view=article&id=84&Itemid=108) costs in comparison to "normal" glass. I guess there is also the cost of replacing the frames.

Surely our double brick concrete walls insulate somewhat better than the wood-type construction used in other countries? If not, how would one remedy this - some kind of special paint (stupid question, I know).

 

[jurgenschairer]

Firstly double glazing has been available in this country for many years and is not a new concept at all. From aluminium, wood to uPVC is available and its not very well knows because of the cost aspect and the low qty's dont allow for major advertising. Having said that the price has come down and it has become a more attainable product.
chrisc4290 mentioned intrude proof glass - this is not double glazing. The idea behind double glazing is that the conductivity between the outside and the inside are broken down by means of an air barrier. With intrude proof glass you dont have a break. The laminate in-between the glass does give you a bit of insulation but nothing close to double glazing.
I see Timber_MG has done some research and he is absolutely right with reference to passivhaus - unfortunately we are still far away from making that a standard because it would be unaffordable for our building industry. In the mean time we can focus on the sans 10400XA legislation that already improves on the current building practises but only touches on to passivhaus. The future is passivhaus. He goes on to say that you can go for aluminium double glazing but as mentioned this is inefficient due to the conductivity of aluminium - although aluminium with a thermal break - plastic insert that divides inside aluminium and outside aluminium. the problem with with plastic windows also known as uPVC windows is a thing of the past as plastic has revolutionised and profiles are now manufactured for the high UV countries - then again we have uPVC windows installed since 1993 and the plastic is still in perfect condition. But one needs to be vigilant as profiles imported from china and turkey are not made for SA conditions. Wood as mentioned has a maintenance issue but consider the wesst cliff hotel - the wood is in great condition with the double glazing installed.

Unfortunately you cannot just refit your current windows with double glazing as the width of the glazing area is not wide enough and the mechanism cannot cope with the added weight.

I have been in the uPVC and double glazing industry for more than 9 years now and the feedback from the clients is clear - it makes a huge difference in heating/cooling and the added bonus is the noise reduction. Our business runs purely on referrals.

for more info check out www.greenwindow.co.za and www.greenbuildingstore.co.za

 

[Timber_MG]

Jurgen, interresting post.

The big problem with our new SANS standard is that it is product-centric looking only at the U or R value (they are inverses of one another one being conductivity and the other resistivity). Simple things like a right angle corner, concrete lintels (common in every house) and a wall running into a steel and concrete foundation cause thermal bridging which undoes most of the good done with a highly insulating window. Once roofing insulation is taken care of these factors are very significant.

I'll get in touch about uPVC extrusions and double glazing.

 

[rodga]

heres a cost comparison between different glazing types I just did for a client

	Glazing type	Single glazing	Low-E single glazing	Double glazing
Window Size
600x600		R 768.49	R 821.35	R 1059.38
1200x1500		R 2127.65	R 2391.95	R 3896.06
1300x2380		R 3967.31	R 4863.21	R 6355.19

 

[Timber_MG]

Juergen, could you perhaps give estimate comparative costing for standard window installations to see what the different framing types add to the cost?

 

[RedViking]

heres a cost comparison between different glazing types I just did for a client

	Glazing type	Single glazing	Low-E single glazing	Double glazing
Window Size
600x600		R 768.49	R 821.35	R 1059.38
1200x1500		R 2127.65	R 2391.95	R 3896.06
1300x2380		R 3967.31	R 4863.21	R 6355.19

/summons the year 2012

Do you maybe have an updated price list?

 

[Pineapple Smurf]

/summons the year 2012

Do you maybe have an updated price list?

Having lived in London for almost 3 years myself all I can say is double glazing windows rocks. Not only for heat insulation but also sound insulation. You dont hear the traffic outside driving past. Very helpful for a master bedroom for those that like to sleep in on the weekends and not have to listen to bikers start up the R1's at 6am and idle for 20 minutes before they leave. @The_Ogre has neighbours like that

 

[RedViking]

Having lived in London for almost 3 years myself all I can say is double glazing windows rocks. Not only for heat insulation but also sound insulation. You dont hear the traffic outside driving past. Very helpful for a master bedroom for those that like to sleep in on the weekends and not have to listen to bikers start up the R1's at 6am and idle for 20 minutes before they leave. @The_Ogre has neighbours like that

Yeah, I reason for me is sound.

 

[Pineapple Smurf]

Yeah, I reason for me is sound.

Are your neighbours still complaining about how horrible you play the electric guitar?

 

[Sargeant]

I once stayed in one of those budget hotels in London during November and was amazed to see that instead of the normal double glazed windows, they had merely installed two aluminum sliding windows in tandem. Did an amazing job of keeping the cold and city noises out. Made me reconsider the need for double or triple glazing. Haven't done a cost comparison but, for me, a much more practical option.