Is it really necessary ?

[Matty]

Hi guy's thanks for the advice on the i controller, all up and running....The consultant came to sign off the job today and now wants All vam unit ductwork lagged.....is it really necessary ????

[The Viking]

From wall to VAM, yes definitely.
This part of the ductwork will be at outside temperature when the system is turned off (and the fresh air one at all times).

After the VAM..
No, or at least not to protect against condensation (here in UK). There might be efficiency gains to be had by lagging this bit but that will depend on the particular installation.

Another thing to question.
What was the original specification?