Ah, the double glazed glass.
First I came to this country I was stunned by all doors/windows. I still am to be honest. Double glazed (or indeed double windows) are the norm where I came from since well before my birth.
But; the next biggest point is the framing of said windows & doors. Even with double glazing you can haemorrhage heat with these frames here. You need proper doorsteps, insulation under the frame all around (between the frame & the wall) and of course seals around the door/window itself. So probably forget these sliding windows, they're a travesty anyway.
Then there's the house itself; when the wind is blowing below it, you need the floor insulated, too, not just the roof! In most cases insulation between the walls would be a necessity, too. It's not even too expensive, in the US they've worked out some impregnated (against flammability) paper-pulp thing that they just blow into the cavity before installing the inner walls; works like a treat.
These houses in Australia (well those I've seen up close) are ridiculously poorly built. And expensive comparatively.
Surprise, no sig. Now there is. Or is there?