> I have PVC windows that after 30 years are as good as new.
Those are unlikely to be uPVC, which means that unless you've reconditioned them, they are uv damaged to fuck. (source: I lived on an estate with a mixture of glazing types.)
> They are large because they have air pockets in them for isolation.
They are large for structural reasons, Insulation is a side bonus. PVC isn't very rigid, so in order to provide some level of support and stop the glazing units drooping out of windows, the frame needs to be of a certain thickness. its not _solid_ for both cost, ease of production and thermal properties. Solid PVC has a uvalue of about 3-5 u depending on your thickness, which is normally better than most double glazing.
> Load bearing window? That's insane idea as well.
What do you think lintels are for? also, how do you think Bay windows work?
> The only thing really thats better is the thermal performance, and price.
I should have added qualified that with the following: installation cost, over 50 years you'll need to replace them twice, if not more.
also, in the UK at least newer glazing has to have vents in them which kneecaps thermal performance.
And yet this uv damage doesn't manifest in any palpable way. It would be very hard for me to tell which of my windows is 3 years old and which is 30.
> What do you think lintels are for?
To direct the load around the window so it's not put on the window?
> how do you think Bay windows work?
I'd hope that they have a separate load bearing pillar between each pane and if they don't, I don't want them.
> I should have added qualified that with the following: installation cost, over 50 years you'll need to replace them twice, if not more.
I have seen zero evidence for that claim. Estimate of their durability vary from 15 to 50 years and my personal experience indicates that it's closer to the second number if not exceeding it.
I had trouble to find and photo of a failed PVC window on the internet. How does the failure mode for them even look like? What exactly fails? If I were to bet I'd say probably mechanical metal parts because they provide much more complex functionality with narrower tolerances than any traditional window. Probably that's the first reason people consider them failed and replace them. I can't really tell if it's the first reason for replacement or second one after evolving esthetic preferences.
> also, in the UK at least newer glazing has to have vents in them which kneecaps thermal performance.
Those vents are there because those windows are insanely air-tight by default. In absence of this, ventilation in the apartments could pull the air out of P-traps because there'd be no other place to pull the air from.
If you have a ventilation system with separate dedicated intake (recuperation) you obviously get the PVC windows without vents. They are available.
Those are unlikely to be uPVC, which means that unless you've reconditioned them, they are uv damaged to fuck. (source: I lived on an estate with a mixture of glazing types.)
> They are large because they have air pockets in them for isolation.
They are large for structural reasons, Insulation is a side bonus. PVC isn't very rigid, so in order to provide some level of support and stop the glazing units drooping out of windows, the frame needs to be of a certain thickness. its not _solid_ for both cost, ease of production and thermal properties. Solid PVC has a uvalue of about 3-5 u depending on your thickness, which is normally better than most double glazing.
> Load bearing window? That's insane idea as well.
What do you think lintels are for? also, how do you think Bay windows work?
> The only thing really thats better is the thermal performance, and price.
I should have added qualified that with the following: installation cost, over 50 years you'll need to replace them twice, if not more.
also, in the UK at least newer glazing has to have vents in them which kneecaps thermal performance.