Pipe insulation used at solar power plants or on solar panels should have an R-value of at least 2. If the pipe insulation of your choosing is thicker than 3/8 of an inch, the value may be closer to 4.
A general rule of thumb is that as the average temperature of a pipe increases, so should the R-value and thickness of insulation.
A general rule of thumb is that as the average temperature of a pipe increases, so should the R-value and thickness of insulation.