WITH THIS TRICK THE INSECTS WILL NOT ENTER THE HOUSE EVEN WITH THE WINDOWS OPEN

Flies: Not Fans of Fragrance
Flies have a strong aversion to certain scents, making aromatic solutions your first line of defense. Harness the power of lemon and cloves; this classic combo not only smells refreshing but also acts as a potent fly deterrent. Simply slice a lemon in half and stud it with cloves. Place these fragrant guardians near windows or doors to create a no-fly zone in your home.
For a more mobile solution, mix a spray using essential oils known for their insect-repelling properties. Combine 10 drops each of mint and eucalyptus oils with half a liter of water, and spray liberally around entry points. This minty mist will keep flies at bay.