I’ve always hated flies.
Depending on the type of windows you have
The top opening ones are the worst.
The flies get in but there is no way for them to get out again.
One way glass – only one side is solid.
This is one sided glass that a fly will bounce off if it’s trying to get into your house.
But it can fly straight through and back outside if its already in your house.
Take extra care to fit the pane the right way round.
The difficulty is in cleaning the glass, you can only clean one side
The optimum speed that the glass becomes ‘porous’ invisible.
If you accidentally put your fingers or hand through it. You can’t bring your hand back without breaking the window .
You have to keep the forward momentum,lest the glass break from them outside
And propel yourself through the window
Then you are free to come through the front door.
Keeping pets in the home is disastrous.