As others have said, it depends on your environment and view. If the house is located in a particularly hostile environment (e.g. west coast Tasmania, central Australian desert) or experiences wild swings between the seasons (e.g. Snowy Mountains) then windows are your friend. In temperate / sub tropical areas like Brisbane then verandahs are the way to go. Windows can have great thermal properties IF they're double glazed which has better insulation properties than say walls in a QLDer house with a timber stud frame sandwiched between weatherboards and VJs. It also depends on the orientation of the house.

Sounds like it needs be reported then. Can (or did) the top sash be pulled downward? Or is that painted shut also?

To Australian Home Designer. Thank you for your advice but I'm not trying to replace the doors with a window. The double glass doors are on the study, and they open onto the very small balcony which measures approx 2M X 0.9M. The balcony has slate type tiles on the floor, there is a roof above and it is enclosed either side by concrete? walls. The balcony has an opening about 2 M wide by 1.5 high, which is what I'm trying to addres. The balcony is next to useless as it is and I could make more use of it if I could enclose it. I tried to add another photo to give a better idea, but for some reason I wasn't able to. So, I'm not trying to replace a window but install something in an open space to act like a window. As this area is considered common property (even though no one else can have access to it unless they walk through the apartment), I have to advise the corporate body. Chances are they'll ask for me to arrange for a by-law to be drawn up. It never ends does it? The other thing I should mention is that Council said (when I first approached them) that the developer would have used every available space to the enth degree. The developer has confirmed this with me. The block is almost 2 years old and all owners are the first occupants. Thank you for taking the time to respond. It is much appreciated.

We had one in our previous home and hardly ever used it because of the layout of the house (kitchen was quite a distance from the outside area the servery served) and the insects. If we had one in our current home, I would use it all the time because the kitchen is more conveniently located and we screened our entire outdoor living area. We are now planning a move and top of the make-over list is a new kitchen with servery window and screening the outdoor living room completely. With the outdoor area screened, there's no need for a servery window screen and outdoor dining is a delight.