Yes, you can insulate between your floor joists, but .....

it's not the most cost-effective first insulation project if you're starting from no insulation. The best is the attic, and then make a huge effort to seal up air infiltration throughout the house (caulking, mostly).

But you have another problem with your basment (aside from the squirrely foundation issues) and that's moisture vapor rising from the dirt. That you interupt with a good moisture retardant material laid directly on the dirt and well sealed at the foundation.

You could also do an air infiltration barrier under the floor (without moisture control); staple it just under your joists it will help prevent cold air getting into your living space. It doesn't insulate, just blocks pressurized air from coming up. But I wouldn't do that until you had blocked moisture vapor at the soil level.

The insulate the walls (of the cellar) first recommendation may not really apply to your situation, and anyway I have read here some comments suggesting that it might do some damage. (I have no opinion about that, I'm just passing info I've seen here.)

But first, you need to get the bulge/settling problem sorted out and at least know what you must do. After that you can decide whether that project is going to happen soon, or will be put off indefinitely. Then it would be time to decide what else you want to do in that space: Moisture barrier on soil, infiltration barrier under joists and/or insulation between joists. If you chose to do it all, I would square away any electrical or plumbing changes (including insulating any water/drain pipes), insulate between joists, install air infiltration barrier and finally install the moisture barrier on the floor.

In addition you need to think through your furnace/boiler arrangements. You may need to insulate the pipes or air ducts, as well. If you create a thermal break between the unheated cellar and the heated living space, you can create problem with your heating plant. I have no advice there as I don't have central heating.

If you're just "itching" (LOL) to get some insulation installed, do the attic first, and soon, as the temps up there will get unbelieveable in just a few weeks.

Or you could take a wait and see approach and resign yourself to having not the most energy efficient house while you experience a full year's life in the building and can make better choices based on what find. There's good counsel in taking a go-slow approach to old house care. Less of a risk of an inadvertent bad choice.

BTW: my personal choice for between the joist insulation is rigid foam sheets.

Molly~

Molly offers sage advise. I've got a brick floor in my basement which is essentially a dirt floor. I have mold problems with it and have temporarily put a moisture barrier on the floor - just some thicker plastic. That, and a case of caulking are the two must-do house-warming projects for any new old-house owner with a dirt floor! That has increased the heat in the winter and decreased the humidity in the summer and the cost couldn't have been close to $50!

My grandmothers house had a dirt floor. Dug it out more and put in a cement floor.

Thanks for all the ideas and the info. I'll check out the rest of the house and see what's up in the attic.
And I'm still trying to find out about this crazy foundation before I do anything!!

As I understand it, foam should never be used w/o a fire-retardant material covering it, like sheet rock. One reason for not insulating a bewteen basement and house is to prevent pipes from freezing. My basement is insulated on outside with foam covered by stucco, but had unsealed cracks letting in cold air, which infiltrated into walls of house. I solved a lot that by caulking to seal gaps all around the house between top of foundation and floor- really amazing what a difference that alone made. Then I went around and sealed every little opening I could find anywhere, such as around windows. My house became much more comfortable with almost no drafts.

I do have wet basement, due to street drainage issues. This is slowly being corrected. Until then, moisture barrier over damp areas and sump pump keep the problem at least under control. Once the street issue is fixed (on the town books), I am going to replace damaged part of concrete floor and intall proper moisture barrier. Dampness hasn't kept me from using the basement, which is a daylight with big slider and nice workspace for studio. In summer I run dehumidifier down there.

Dayle Ann