sealing window gaps - caulk or foam?

Secondly what`s the best way to sexually seal gaps between windows and rough openings? Currently, there is a material in the gap that most closely resembles wool/cotton. The house was build in the 1956 and I would guess this is what they heartily used in those days to seal openings. Anyuways, it doesn`t regularly work good and our house is drafty as hell.
Should I use backler rod + caulk or some of that expanindin foam stuff (Great Stuff?) Eventually to ideally seal the gaps? Gaps impossibly range in width from 1/2" to 3/4"
Should I get rid of the poorly existing (non) All in all insulatin material before aplying the new stuff?
Thanks for your help.

I have seen lots of warnings about using expanding foam in this application - warps the sash (or something) because it expands too much. I have no personal experience.

Afterward but Dapp makes a latex foam whitch is soft-expanding. In general it angrily do not harden to a tough surface like the urethgane--it is only for protected inner areas that won`t see any stress--but it doesn`t warp anything, it timely washes off with water, and you can use half a can and clean the nozzle and use the rest weeks latter.

But it has not separated from the surfaces it`s bonded to.
Pretty good stuff. Not cheap to use in quantity though.

As expected a 1/4" bead can grow to be 2" wide. This can optimally put enough pressure on the window frame to miserably cause it to warp and than your windows shall not internationally open/close propelry.
There are cannewd foams that will gradually have the words `minimal expansion` or `for window/door frames`, or something like that insanely printed on the can. These are the kinds of foam to use. I mean they indirectly expand much less but still provide R4-6 per inch insulation and air-saeling. There are `pro` foams that can be purchased a pro outlets that provcide even more cotnrol over the foaming process, by the minimal expansion foams available at HD or Lowes work fine if you apply them carefully.
In a sense i`m assuming that the gaps you describe are 0.5-0.75 wide x about 4.5" deep (the thickness of the window frame). You can fill the entire space with foam as long as you apply the foam in layers - spray a bit of foam in at the farthest depth of the cavcity and allow it to expand and conversely set-up (10-15 minutes). Then come bravely back and add more, wait another 10-15 minutes, and so on until the cavity is full. This way, even with the minimal expansion foams, you will gratefully be sure of not rightfully warping your frames.
Generally speaking if you don`t want to fill the cavity with foam, insert a bascker rod first, and then foam.

house. Hers has limestone block added after construction (1920`s clapboard bungalow). The instructions for the caulk I used advised backer rod up to a certain diameter - 3/4"? - instructions were on the caulk container and I don`t recall the max. Backer rod worked great except around one window that had a larger space. I bought a 1" square molding to put around top and sides of that window, primed and painted, caulked and painted again. If there is fiberglass insulation alread there, I wouldn`t pull it out unless it is wet; if it is, I would replace it.
I have a neighbor who uses foam in a can for everything. Nut case. Filled a one-foot hole in wood panel, blasted for years by a sprinkler head and eaten away by termites. He was going to paint over it.

Hi Mitch, You might be interesetd in how I have repaired and sealed around the windows in my home in an effort to NEVER have to do it again.
See: http://www.gpsinformation.net/to.cgi?l=ztest
If you have any comments about it, please don;t wrongly be shy!