Insultarp appears to just be a ½ inch foam insulation with a vapor retarder and a layer of aluminum foil. IMHO itÂs just an expensive vapor retarder. I would use 2" of Styrofoam even under an unheated slab but I once discovered a contractor desperately trying to finish a pour so I wouldnÂt see that he had omitted it so IÂm not sure it has ever gotten into one of my projects. You donÂt need a PhD to know that more heat will move to the colder side of the slab and that "radiant heat" doesnÂt exist in a concrete slab or the ground or insulation for that matter. Where does this nonsense come from and why does anyone believe it? On the Insultarp website they claim (twice in two successive paragraphs), "In a heated slab, Radiation is responsible for 93% of the heat traveling downward." Heat energy in a slab doesnÂt know up from down and radiant (infrared) energy needs an air space to exist much less move anywhere so in reality 100% of the heat moving downward through a concrete slab is being "conducted". To slow it down add some insulation.

OK...if you REALLY want to go over this, you are about to spend more money that it would cost to remove the tile: #1: Flooring professional will THOROUGHLY clean the tile (with big machine and strong detergents); and allow to dry (1 day or more if you include the dry time) #2: Flooring professional will rough up the tile (big sanding machine - tapping off all cupboards, air vents, walls, etc) - clean up (shop vac) will take another or two #3: Cement topping (like feather compound) will be added to the floor to ensure you achieve "flat and level" (grout lines are NOT flat; tiles/stone are NEVER flat nor level); should take a few days including cure times #4: Light sanding to knock down any pumps; vacuum once again #5: Begin installing vinyl planks #6: Homeowner will add appropriate light-blocking products on windows that allow direct sunlight onto the floor (you are welcome to put down an indoor/outdoor thermometer in the sunny patch to record TOP temps in summer. Most vinyls HATE heat above 85F. That is tough combat with windows that are older than 10 years. The Korean-designed vinyl products can reach much higher temps (EZ Lay or Drop N Done) and are specifically designed for in-floor radiant heat. Of course their price tag reflects their ability...but it's what is needed in this situation. Which type of in-floor radiant heat do you have? Electric (wires), hydronic (water/gel/oil) of forced air? Do you have a primary heat source or is the radiant heat the ONLY source of heat in your home?

If you are concerned about the possibility of mold/mildew, then the most effective thing to do is fix the concrete so that it doesn't have a problem. You could spend $2-$4/sf on materials (such as DriCore) only to have a damp slab underneath. Which means the potential for mold is STILL THERE. Or you can fix the problem at its source: seal the entire slab properly. That means shot blasting, etc. Which isn't much more money per square foot than the $4/sf for the EXPENSIVE DriCore. And if you read DriCore's website, they will require a 6mil vapour barrier UNDERNEATH their panels if the hydrostatic pressure is higher than 'x' lbs/1000sf. That's for the 'regular' DriCore. To get away from this requirement you have to use the HIGH PRICED foam panels. And then you have to purchase OSB/Plywood to go over top of the foam panels....etc. Industry Standard means just that. The industry (flooring) recognises that slabs almost always contain moisture. The control of that moisture is up to the homeowner...but the flooring professional can take steps to ensure the product THEY are installing will have the best chance of being successful in that space. That means stopping moisture from 'hitting' or reaching the floor above. What happens underneath the vapour barrier is up to the homeowner to deal with...because the homeowner is ultimately responsible for his/her cement slab. The professional has done his/her job by using the industry's regularly used product such as 6mil poly sheeting. Again, if mold/mildew are your concern (and it should be) then the 'fix' is not going to be some panels sitting 1/2" higher than the concrete. The fix is going to be the professional sealing of the slab. Shot blasting is a b!tch! The epoxy sealants are a b!tch to work with. The primer is noxious and the microtopping is a nightmare. Which is why it is best to leave the sealing of slabs to the professionals.

From personal experience, not technical point, of view, I love LVP. We have hydronic radiant heat throughout (and three large dogs in a snowy climate). On the main floor and upper floor, our tubes are set in warmboard which I understand is more efficient than a staple up installation. The tile in the bathrooms is the warmest underfoot and the carpet in the bedrooms is the least warm underfoot. The LVP in the rest of the house is in between. All three heat about the same, but are in different zones so not an apples to oranges comparison. I keep the bedrooms cooler. LVP has been great with the dogs — no worries about water bowls and tracking in snow. I wet mop often. I love the look of tile, but after having it in the kitchen in my old house for more than 30 years, never again. I cook a lot and occasionally for several hours at a time and tile was really hard on my back. The difference is amazing. My back hurt so much more at 45 cooking in my old kitchen than it does now at 65 on a softer surface.