913. Determination by appropriate tribunal; matters to be considered or disregarded.

In making a determination of rent1, there must be disregarded:

  1.  

    (1)     any effect on the rent attributable to the granting of a tenancy2 to a sitting tenant3;

  2.  

    (2)     any increase in the value of the dwelling house4 attributable to a relevant improvement5 carried out by a person who at the time it was carried out was the tenant6, if the improvement was carried out:

    1.  

      (a)     otherwise than in pursuance of an obligation7 to his immediate landlord8; or

    2.  

      (b)     pursuant to an obligation to his immediate landlord being an obligation which did not relate to the specific improvement concerned but