Feed and return pipes too close together?

[Johnytuono]

Have just been looking at my central heating pipework and noticed that on a couple of runs (that are also situated under rectangle plastic trunking) that the copper pipes actually touch each other for 3 inches or so before branching out to less than an inch apart. Also on another run (again under plastic trunking) the pipes are roughly an inch apart over a 10 foot run. Surely this would affect my. return/flow temps. at the boiler? If so, is it worth getting heat shield tubing and again, if so, would it be best to shield the return or the flow or both even?
Thanks

 

[Madrab]

It's always best practice to insulate any CH pipework where practical. Any losses that can be minimised would be a saving.