We often get asked how to deal with this. The very best solution is below:
1. Wrap the pipe with FT55AL Pipewrap overlapping at joins. The rolls are 5.5m x 1.2m. If the material is cut lengthways in 400mm strips you will get three strips at 5.5m long. This is enough to cover a 100mm diameter pipe 16m long.
2. For aesthetics box the pipe section in using double plasterboard sheets on timber frame and stuff it with any left over fibreous insulation.
Note: More than one layer of wrapping material can be used for greater effect. This is particularly advised at right angle bends.
If you want to gain even more noise reduction you can stick the self-adhesive Tecsound 50 Acoustic Membrane around the pipe first, overlapped at joins as before but obviously this will increase costs and is often only viable for extremely sensitive applications.