Turning to the amount of damages awarded, “the proper measure of damages for breach of the warranty is the difference between the fair market value of the premises if they had been as warranted, as measured by the rent reserved under the lease, and the value of the premises during the period of the breach” (Park W. Mgt. Corp. v Mitchell, 47 NY2d at 329; accord Stone v Gordon, 211 AD2d 881, 881-882 [1995]). There is no dispute as to the rent charged under the lease and, inasmuch as the breach was severe and persisted throughout plaintiffs occupancy due to defendant’s inaction, Supreme Court properly determined that the rental value of the premises was halved (see Park W. Mgt. Corp. v Mitchell, 47 NY2d at 329; Matter of Nostrand Gardens Co-Op v Howard, 221 AD2d 637, 638 [1995]; H & R Bernstein v Barrett, 101 Misc 2d 611, 614 [1979]).