The answer will vary from state to state; how about that?
See: "§ 17.06 The Implied Warranty of Habitability: New Common Law [247-254]
[A] Nature of Implied Warranty
In the 1970s, courts began to recognize a new tool in the fight against substandard rental housing: the implied warranty of habitability. Under this doctrine, each residential lease is deemed to contain an implied warranty that the landlord will deliver the premises in habitable condition and maintain them in that condition during the lease term. See, e.g., Hilder v. St. Peter, 478 A.2d 202 (Vt. 1984). For example, broken windows, leaky roofs, or rodent infestation normally render a rented dwelling uninhabitable.
[B] Remedies
In general, the tenant must notify the landlord of the defect and allow a reasonable time for repairs to be completed. If the landlord fails to act, the tenant may remain in possession and also: (1) withhold rent; (2) sue for damages; or, in some jurisdictions, (3) repair the defects and deduct the cost from rent due the landlord. Alternatively, the tenant may terminate the lease and sue for damages."
Quoted from:
Property - Chapter 17