Hello has anyone put in, in floor heat ( hot water ), without foam board in the floor?? In my dairy barn milk room and parlor I put 2 inch foam board with the water lines stapled to it, then 3 to 4 inches sand then cement , it works well I use a gas water heater. A friend used a water heater for years in his 40x42 shop only replaced because he thought the in side flue was rusting. I seen on YouTube that some people are not putting insulation board down, when I did my barn I think that there was a bubble wrap product some were using , it worked as insulation and vapor barrier. I would use foamboard vertically on the outside walls between cement and outside walls. this will be a farm shop set at 40-50 degrees. thanks Bryan