Ditra underlayment is wonderful (the orange waffle barrier), and you should be good to put that directly over the slab. The floor will be cooler if it isn’t heated underneath because that’s just what happens, but not more so than wood or vinyl. The Ditra is thick and a good thermal break.

I've used Ditra above grade. But, below-grade, Delta FL which is specifically designed for basement flooring.

I've personally sold 6mm cork underlay + 1/2 cork floating floor to a homeowner in NORTHERN Saskatchewan (the Northwest Territories' boarder was only an hour drive away). She put it in her basement. The basement is now the WARMEST spot in the house. The cork flooring and underlay raised the temperature in the basement by 7 C (12 F). It is also the quietest spot in the house. And the cushion on that floor is impressive.

The winters in that area = -50C for weeks at a time. If cork+cork can help in this situation...it is going to be warm enough just about anywhere in N.America.

If you use cork on cork...you don't have to do anything 'expensive' like a dimple membrane. A $0.06/sf vapour barrier (6mil poly sheeting) + red duct tape (moisture resistant) is all you need.

I've sold dozens and dozens of cork + cork flooring products in Canada = cold climate. I've never had anyone come back and say, "The floor is too hard. I can't believe I listened to you." Never.

And I've only had one complaint about temperature issues with cork+cork in a basement. The homeowner used 6mm cork underlay + 1/2" cork floating floor. The hubby LOVES it...the wife (mid 50's and going through 'The Change') finds it too HOT. The basement doesn't drop below 21 C (70 F) even with all the vents closed off to the area.

That's the ONE complaint I've had about a basement install with cork+cork as the option. It was too WARM. Sigh...I tried to tell hubby to go with the 3mm underlayment...but he thought 'thicker is better' but forgot about how difficult it can be for someone who runs 'too hot' to live in a space that is too warm.

Hi SJ! I am in the middle of a basement renovation and the contractor needs the flooring next week. The subfloor is concrete and my biggest concern is warmth as my kids will be playing down there. Could I put a cork underlayment directly on top of the concrete and then the LVP on top of the underlayment? The LVP would have an attached underlayment but I assume it will only help to make the floors warmer? Let me know if you think there are any issues or any flooring you recommend particularly to help with warmth. I was also considering buying Dri Core instead of the cork underlayment as the R Value looks much higher. Any advice would be much appreciated!