83.63  Casualty damage.--If the premises are damaged or destroyed other than by the wrongful or negligent acts of the tenant so that the enjoyment of the premises is substantially impaired, the tenant may terminate the rental agreement and immediately vacate the premises. The tenant may vacate the part of the premises rendered unusable by the casualty, in which case the tenant's liability for rent shall be reduced by the fair rental value of that part of the premises damaged or destroyed. If the rental agreement is terminated, the landlord shall comply with s. 83.49(3) [F.S. 1973].