There are cracks up to a quarter inch wide between the the window frame and the inside window trim. It had been letting in cold air and leaking out warm air out for years. I had not done anything because I tolerate cold better and always set my thermostat to 72 deg F. The average gas bill hasn't changed for years and the furnace wasn't exactly knocking itself out unless it gets to minus twenty deg F or C. Its an unreliable measure of energy loss for sure.
The window frames were tight and secure to the stucco finish so there were no repairs or caulking possible there without making the problem something major. Same thing inside the house. The window trim was also tight and secure against the wall. No adjustments were possible. I didn't like the idea of those aerosol cans of squeeze foam insulation as they are sticky and would be impossible to remove if they didn't work and I come around to redoing the window repairs. This is indeed fortunate because I chatted with my neighbor and he said never to use that stuff. He did and the foam accelerated the cracks in his windows over the years and he has a real problem now. My other porposed solution was to stuff the cracks with fiberglass insulation and glue or nail a thin slat of woodover the whole inside window trim to cover the repairs. I have a well equipped garage workshop and can do that except I procrastinate (long story).
On saturday my sister stayed over (I live alone) and refused to sleep in the leaky cold bedroom preferring the sofa. By the morning she insisted on fixing the cracks and asked for those 1/4 inch rolls of sticky backed foam tape weatherstrip to at least temporarily close the cracks. Then she found I had leftover laminate flooring underlay foam sheet scraps. She used these instead and they are an excellent material as they are formulated for years of servive as flooring underlay. They are also strong and flexible and therefore will conform and fill the cracks to the edges. I love the solution. I wasn't too impressed with the foam weatherstrip material as they lose their elasticity and therefore seal effectiveness after a season or two. They are also hard to trim to size to fit the cracks.
My next step is to find a roll of self adhesive vinyl shelf liner contact "paper" with a suitable design and use that to finish the window trim and cover the cracks. Sis had asked for duct tape or transparent box tape, a pretty ugly, temporary idea (they dry up and deterioate) that leaves a messy residue when its time to remove them.
I am a pretty happy man. If this fix doesn't work I can easily undo everything without risking a messy cleanup. But I am confident that the fix will be good for years and I can always do the same fix at some future time should that become necessary.