Cold floors make an otherwise welcoming house uncomfortable. Determining the cause of cold floors, however, is usually fairly simple and can be addressed without massive expenditure. Some issues are structural and logical: you can expect the stone floor of your screen porch or the basement linoleum laid on cement to be cold, and carpet is the logical warmer. Different strategies, however, are needed for floors that should be warmer than they are.
Perform a simple test to determine whether cold is radiating from a floor over a crawlspace. Dampen your bare hand with a wet rag and hold it 1 to 2 inches above the floor. If you can feel cold radiating toward your hand, you have found your problem.
Address the damp and cold coming up from the crawlspace by covering the entire area with a plastic ground cloth. Spread one or more pieces of heavy weight plastic sheeting and anchor it down with rocks, bricks or lumber scraps. Do not pile sheeting against the crawlspace walls or supporting pillars, and do not tape sheeting to them either. Although this seems like it would provide more insulation,, it can produce moisture collection against structural surfaces and promote water damage. Loose edges allow runoff or moisture to dissipate in case of a soaking storm or thawing ground.
Measure spaces between the floor support beams and purchase roll type fiberglass or foam slab insulation to fill the spaces. Install the insulation with the moisture barrier facing the floor, not the ground. Roll insulation can be attached to beams with a heavy duty staple gun. Find brackets or use large nails, hammered into support beams, not the floor, to hold foam slab insulation in place.
Do the wet-hand test again to locate the source of drafts. Follow it up by holding a lit candle within 4 to 6 inches of possible draft sources. Some, like a fireplace, are obvious. Make certain the damper closes completely, and cut a piece of plywood to fit into the fireplace opening if heat loss is chronic and severe. Remove it only when you want a festive fire for a special occasion.
Weatherstrip doors that cause frequent drafts. Whether you need to do the whole door or just put a draft blocking strip at the bottom will depend on the door and the severity of the drafts. This usually requires only weatherstripping supplies from the hardware store and a hammer or screwdriver.
Examine floor edges for draftiness. Especially in an older house, baseboards and quarter-round may have been removed to accommodate wall-to-wall carpeting. If they were not replaced, putting in new moldings will reduce drafts noticeably. In older houses, aging makes wood shrink and dry. Even existing floor moldings may let drafts through. In this case, remove the moldings carefully. Place roll-type insulating putty or a small line of spray insulation foam where the wall and floor meet. Replace the moldings. Again, the change will be noticeable.