There's the Italian word serramento which means "a window or a door", used in this way for example:
Our company produces [serramenti] in aluminium.
Is there an equivalent word or expression that refers to doors and windows in general in English?
It is common to use the phrase 'doors and windows' as a class of objects that is part of a construction (typically part of what is known as joinery and woodwork). This suggests that there is no widely used and understood single word for this purpose.
In certain technical contexts, doors, windows, ventilators, etc., are collectively referred to as 'openings'. (I could say openings increase the cost of a concrete structure.) You will notice that openings could be understood to be framed (in wood, metal, etc.,), rather than just an absence of material.
"portal" seems to cover both doors and windows, although only widows that open as opposed to panes of glass that can also be referred to as windows but not portals.