There are usually more economic ways to insulate the rest of the basement walls, especially if this is a DIY project.

OK, shoot. Tell me more.

It's not an economic thing, I just don't want to insulate where it's not needed.

See link for the US Department of Energy recommended insulation levels for different parts of the US.

Even if economics don't matter--meaning that you don't care about reduced heating or cooling costs--appropriate insulation levels will make your home more comfortable.

I was referring to the costs of reaching the appropriate insulation level in a basement; usually, sprayed foam is the most expensive method.

Here is a link that might be useful: Recommended insulation levels

I get the spray foam for free from work (left overs from 2-3 jobs should be enough). That article was informative but didn't ansewr the question. At what point does the ground outside the wall provide enough insulation? Homes built into the ground (from what I've read) don't need insulation because the ground stays at a constant, comfortable, temp.

Four feet down, the year-round average is usually 50Ë-55Ë F, except Alaska, where there is permafrost-and all the places where four feet down is below the water table.

By the way, earth itself is a poor insulator--only R2 per foot.

Here is a link that might be useful: Earth Houses need Insulation