RWP/SVP are often located in the corner of a wall and thus are hidden by a two sided encasement to box them in. Sometimes they are away from the corner and in such circumstances would require a 3 sided encasement to box in against a wall.

 In use these can generate unwanted noise so the encasement to box in should be a high level acoustic specification to dull this noise as much as possible. 

A typical solution often used on site would be to wrap the pipe in glasswool insulation first then encase with two layers of dB Board.

There is guidance on this construction in Approved Document Part E (Section 4.45), but often the project acoustician will stipulate the minimum requirements.