In addition to all the sprays and stuff ....
to prevent new flys coming into the house,,,,
How about mesh screens on the windows?
Those will have to be on all windows that will be opened.
This can be a big operation but quite effective even against other unwanted insects like mosi and roaches.
So can keep windows open till quite late in the night.
හැබැයි Full seal වෙන්න ඕනේ. මම use කරා velcro, ජනේලේ අරින්න වහන්න පුළුවන් වෙන්න.
There are other fixing ways too.
There are little negative points too. Air flow bit reduced, light may be bit reduced,
dust collects over time so have to clean from time to time....
Now... doors are a bit of a problem.
We keep all doors closed. Only few door going out. But these damnd flies would come
in when door is opened and someone is going through.
Air curtains is one way. But they are rather high price. For some it may be a neat solution.
So have table or pedestal fan on high speed directed at door. Have door switch to
on/off fan. ඉඳල හිටලා මැස්සෙක් ඇතුලට පනිනවා. Minor matter.
May be can have two fans to cover entire height of door.

Anyway we don't have huge number flies outside.
Also we not going in out all the time.