Is R2.7 enough for a thermal break for a basement cement floor

A homeowner planning to cover a basement concrete floor asked whether a thin insulating underlayment would be enough to take the chill out of the slab before adding vinyl plank flooring. The floor already has plastic sheeting under the concrete but no insulation, and the homeowner wanted to add no more than an inch of thickness. Two products from a brand called Dricore came up: one with an R-value of 2.7 that combines foam with a layer of wood sheathing on top, and another with an R-value of 4.1 that is foam alone. R-value measures resistance to heat flow; higher numbers mean better insulation. The homeowner leaned toward the lower-R product partly because pure foam under vinyl flooring seemed too soft to support furniture legs.

Responses from experienced builders in the discussion said the thinner, R-2.7 option would likely be enough for comfort. They explained that bare concrete feels cold mainly because it conducts heat away from your feet quickly, not because it's dramatically colder than the room. Any layer between the slab and your feet — foam, sheathing, even plastic — cuts that conductivity and improves comfort. One builder noted that untreated concrete typically has only about R-0.3, so adding R-2.7 is a meaningful upgrade. They also agreed that soft flooring laid directly over plain foam, with nothing more rigid underneath, can feel mushy and is best avoided.

For anyone with a similar basement floor, this suggests that a thin insulating underlayment, even a modest one, can noticeably improve comfort and may also help avoid moisture problems in summer, without needing a thick or complicated buildup.