In article , 00_CumPeeWearD12 @gmail.com says... :) Thanks for the info... So, what can I do to fix it? If there is something :) in the attic, do I have to call a specialist to clean/kill or spray some :) chemical or do whatever they need to do to fix the problem? :) :) The remedy, if any needed, depends on the species of fly. You probably are dealing with cluster flies, though there are others that will have the same practice of getting into the attics to wait out Winter. If there are just a few a day wait them out till Spring, if it dozens to hundreds at a time on a warm day an attic treatment may be needed, though it is just reduces the population, many may be in the walls not bothered by any insect treatment. At the end of the Summer an application by one of the pyrethroid insecticides can really help by treating the exterior of the structure. Caulking obvious cracks on the exterior, though as with most homes it is impossible to get all the areas they may gain entrance.
If it is one of the flesh eating species, you probably would of noticed the dead animal odor. The odor attracts the flies, they lay eggs, the maggots consume the carcass, then they pupate to flies and the cycle starts again. If you are seeing these type of flies, the source is already gone and the flies soon will be gone on their own.
If it is just the common house fly, is there a source near the home such as a compost pile, dog runs, etc. Then you may be dealing with large outdoor population with a few getting in. Removing the source, and making sure the windows/doors are caulked and close well is usually all that is needed.