Can someone share your experience the pipe is expose outside, there will be burning when accidentally touch on the hot water pipes.

Quite common sense isn't it?

All heat-fluid carrying piping need to be heat-insulated for heat not transmitting to ambience surrounding(energy loss), and for safety reasons (human touch....)

In this case, the heat-insulated material need to be water-proof somehow.

In toilet or bathroom, I insisted no wooden fixtures, no mercury mirror, try use stainless steel A204 screws...