a rental agreement or with Section 5-12-070 either of which renders the premises not reasonably fit and habitable, the tenant under the rental agreement may deliver a written notice to the landlord specifying the acts and/or omissions constituting the material noncompliance and specifying that the rental agreement will terminate on a date not less than 14 days after receipt of the notice by the landlord, unless the material noncompliance is remedied by the landlord within the time period specified in the notice. If the material noncompliance is not remedied within the time period so specified in the notice, the rental agreement shall terminate, and the tenant shall deliver possession of the dwelling unit to the landlord within 30 days after the expiration of the time period specified in the notice. If possession shall not be so delivered, then the tenant's notice shall be deemed withdrawn and the lease shall remain in full force and effect. If the rental agreement is terminated, the landlord shall return all prepaid rent, security and interest recoverable by the tenant under Section 5-12-080.
(b) Failure To Deliver Possession. If the landlord fails to deliver possession of the dwelling unit to the tenant in compliance with the residential rental agreement or Section 5-12-070, rent for the dwelling unit shall abate until possession is delivered, and the tenant may:
(1) upon written notice to the landlord, terminate the rental agreement and upon termination the landlord shall return all prepaid rent and security; or
(2) demand performance of the rental agreement by the landlord and, if the tenant elects, maintain an action for possession of the dwelling unit against the landlord or any person wrongfully in possession and recover the damages sustained by him.
If a person's failure to deliver possession is wilful, an aggrieved person may recover from the person withholding possession an amount not more than two months' rent or twice the actual damages sustained by him, whichever is greater.
(c) Minor Defects. If there is material noncompliance by the landlord with the rental agreement or with Section 5-12-070, and the reasonable cost of compliance does not exceed the greater of $500.00 or one-half of the monthly rent, the tenant may recover damages for the material noncompliance or may notify the landlord in writing of his intention to correct the condition at the landlord's expense; provided, however, that this subsection shall not be applicable if the reasonable cost of compliance exceeds one month's rent. If the landlord fails to correct the defect within 14 days after being notified by the tenant in writing or as promptly as conditions require in case of emergency, the tenant may have the work done in a workmanlike manner and in compliance with existing law and building regulations and, after submitting to the landlord a paid bill from an appropriate tradesman or supplier, deduct from his or her rent the amount thereof, not to exceed the limits specified by this subsection and not to exceed the reasonable price then customarily charged for such work. A tenant shall not repair at the landlord's expense if the condition was caused by the deliberate or negligent act or omission of the tenant, a member of the tenant's family, or other person on the premises with the tenant's consent.
Before correcting a condition affecting facilities shared by more than one dwelling unit, the tenant shall notify all other affected tenants and shall cause the work to be done so as to create the least practical inconvenience to the other tenants. Nothing herein shall be deemed to grant any tenant any right to repair any common element or dwelling unit in a building subject to a condominium regime other than in accordance with the declaration and bylaws of such condominium building; provided, that the declaration and bylaws have not been created to avoid the application of this chapter.
[See the rest of the section for full details.]
Basically, YES, you can, by city code, break a rental agreement if you follow the correct procedures.