Advice on buying and owning an awning
Whether the curtains are closed or not, once the heat is through the glass your interior room temperature will rise. An awning keeps the room cool by casting a shadow on the window and blocking sunlight from reaching the glass.
That very much depends on the application and the window but it should extend past the window opening by at least 200mm (8 inches) if possible. The projection depends upon how much of your patio you want to cover but generally the maximum projection will be about 500mm (20 inches) less than the width.
A maximum projection of 3500mm (140 inches) is recommended.. The amount of shade you get will vary with the time of year.
The awning will be fitted with substantial bolts, drill size 10/12mm (1/2 inch), so the wall needs to be in good condition. Deans surveyor will check it out to make sure and most problems can be overcome by using special plates to spread the load or chemical fixings to bind together a suspect area. Sometimes special extension brackets may be required - especially on bungalows or single storey extensions.