Don't the pipes themselves have some insulation?
Depending on the state and council requirements you don't have to "lag" (insulate) pipe work. In our opinion lagging pipes is a must!
External copper pipes whether it is hot or cold water. Cold water pipes need lagging to stop them freezing and in the summer it will stop the tap water coming out like bath water. Hot water pipes need lagging again to stop them freezing in winter and also help with getting hotter water to your shower or tap because the water won't be passing through cold pipes
Internal pipes are fine because most of your pipes will be kept at room temperature
Hope this helps!!