Insulation, Radiant and Vapor Barriers - Insulating an old floor and wall

I'm not sure where to put this, but I think this forum might be right...

This has to do with insulating underneath a floor / wall edge, but here is some background first: I recently moved into an old row-home (turn of the century). The bedroom is on the second floor, which has an old, not particularly well-done, hard-wood floor (probably pine). There are many places in the floor where the boards have large spaces between them, some as wide as an inch. Someone had previously gotten "a floor guy" to come in and fill the spaces with some kind of... resin? that hardened. He told them it wouldn't last long, and it didn't. In most places it is coming up in pieces or has developed similarly large cracks, if it is still even there at all.

It's gotten colder recently, and I've started to notice a large amount of drafting in this room. I've traced a lot of it to coming in from underneath this floor, and up through many of these cracks. The worst problem is in a far corner, where the wall is to the outside. Some of the flooring is cracked and I can see through it that there is no insulation underneath the floor at all. There is also a large amount of drafting coming through the cracks in that corner and also in the edge between the (adjoining outside) wall and the floor.

Now, I am currently renting. The landlords are very helpful, but have told me that they realize there is a problem with the floor, but don't want to replace it until the next renter (whenever that is) since I am already moved in. At one point they offered to get an area rug for the room to try to help (I'm not sure it would, especially with draft coming from between where the wall meets the floor).

I know there are types of insulation you can spray into places. Would something like this be useful for spraying under the floor joists, or would that just be a waste? Also, does anyone have any advice on how I might be able to improve the drafts coming in from between the wall and floor - or should I just go for the carpet and hope for the best?

Thanks!!

First of all I hope that you dont have to pay for heat as a renter. Since its not your place you are limited as to what you can do. It sounds like there is a big leak in what people call the band joist area btw the 1st and 2nd floors and or the walls have no insulation. Understand that no matter what cracks you seal up the floor will probably be still super cold due to the cold air flowing underneath it. Ask your landlords if they will come in and redo the resin thing at least. If they pay for the heat tell them what a big money waster it is to keep letting all that cold air in there.
If you pay for heat then tell them that a rug wont do it for you and you will spray some great stuff foam in those large floor cracks. It wont look pretty though but will get it done. After the stuff dries you can cut off the excess easily to make it flush. Next take a tube of clear 100% silicone caulk and fill in all the smaller cracks. Caulk also all around the baseboards of the room both the top and bottom of it. That should take care of the drafts but then you should still get an area rug cause the floor will be still cold. Good luck.

I actually do pay for heat... which is one of the reasons I was so concerned about doing all I can to improve the situation.

Thank you so much for the suggestions, I am going to look into it and talk to the landlord and see what we may be able to do.

Thanks again! :)