Ornamental bird houses look sharp. Sometimes they include an entire mansion for birds, with various “rooms” and a fence. One ornamental bird house I saw recently looked like a canoe.
However, these ornaments are just that. They are not designed to be safe homes for birds. They are generally too small for a nest of birds. They do not have any ventilation and would be dangerously hot. If you have one of these, plug the hole so birds can’t nest in it.
Choose or build bird houses without ledges or perches. Ledges collect rain water which may lead to mould. Perches could allow other birds access to prey upon the nest.
Air holes for ventilation are important, too. Like you, birds like a cool room and can’t open a window if there isn’t enough ventilation.
Birds are looking for nest sites now, so don’t delay.