A radiant panel having a channel or groove is manufactured using, for example, a simple U shaped channel with substantially parallel vertical sides is one embodiment. Because varied diameter tubing pressed into curved channels of varying radius will change their shape from round to oval by different amounts, channel width will be reduced at curved channel areas as appropriate, in light of tubing size and channel radius. This reduction in curved channel width compared to straight channel width will allow for a consistent friction force to be developed upon pressing the tubing into a channel, for retention purposes, regardless of whether the channel is straight or curved. In other embodiments the depth of groove may be varied as well to allow for the increased vertical dimension of tubing which is deformed from round to oval by bending forces. By varying the depth as necessary, tubing can be installed consistently flush with the surface of the radiant panel which enhances the installation of covering materials whether they may be finish floor materials or wall or ceiling finishes. Varying width and depth will also tend to maximize the contact area of tube to conductive surface, thereby improving the flow of heat from tube to radiant panel.