What are some ways to insulate a concrete slab type foundation in an older home built in the 1950's? As far as I can tell, the slab is not insulated at all and results in a very cold floor and living environment on the first level of the house in the colder seasons.
Has anyone used ceramic insulating paint applied to the top of the slab in these circumstances?
Are the walls insulated? If not, do that first. Most of the heat escapes there...especially the part nearest and above the ground level.
With a fully insulated wall, you might not even need to insulate the slab. in MN we insulated our walls and then left the concrete floor as-is (stained it). Only on the coldest winter days did we need to turn on the fireplace and when we did, the slab was fine comfort-wise.
Otherwise, the most typical way to insulate the slab will be with foam board. Typically EPS or XPS with a floated plywood subfloor on top.
But if you have no intention of ever finishing the basement, maybe insulating the first floor underside might make more sense.
UPDATE
The above is valid for a house with a basement. I misread your question initially. It appears you have a floating concrete slab as your foundation. To insulate that you need insulation...either under it (preferred) or on top of it. Obviously adding insulation underneath is not practical after the fact.
The cheapest solution is likely just a new floor covering...carpet with a think pad...maybe cork, etc.
More complicated, but doable, would be to lay down EPS or XPS and then a floor on top of that. The trick there is that this will change the height of your floor...likely causing issues with doors, thresholds, cabinets, etc.
Cold cement floors in cold climates are a fact of life. As DA01 says, most heat escapes through the walls and ceiling, NOT the floor.
The go-to answer to combat cold floors in well-trafficked areas is a radiant floor heating system; it's basically an electric blanket that goes in as an underlayment to tile, laminate or hardwoods (might not work well with vinyl/linoleum), and has either a water tube or a resistive heating element that heats the floor surface from underneath. They're not cheap, especially as they often have to be custom-fit to smaller areas like bathrooms or kitchens, but in many northern homes they aren't considered luxury items either.
