Gaps where the window trim meets the window frame inside the window.
Gaps between window frames and walls inside.
For large exterior gaps mainly ones wider than one centimetre you may be better off using mortar.
If the insulation is fiberglass this can be dangerous as the fibers can be inhaled causing lung.
In either case gaps around a window frame are not good and can lead to damp penetrating the internal walls window frames and beyond.
But if done incorrectly it can lend a sloppy amateurish look.
Seams where the window trim meets the walls.
On your home s exterior caulking windows is needed in the same places.
Come spring add or replace weatherstripping for a longer lasting fix.
Gaps can appear around any type of window frame on a house of any age.
Caulk seals the gaps between the window trim and the siding on your house.
If your gaps are even larger you may wish to consider using expanding foam.
Caulking windows to give them a finished look inside and out and seal out leaks and drafts is a fairly common diy task.
Such stopgap measures eliminate air leaks by sealing sash perimeters from indoors.
They may be caused by natural settling of the house cracking existing mortar or just by bad workmanship when the window was fitted.