There is no set rule, The regular rent for your apartment represents the value of the apartment in proper condition with adequate heat. An apartment is rarely worth zero rent, unless it is in really poor condition. Some landlords may respond to this by bringing eviction proceedings against you. If you have followed these procedures properly, you should be protected against eviction. In some cases, the court may even order the landlord to pay for your attorney's fees.
Some landlords try other retaliatory tactics.
If your landlord tries to evict you, raise your rent, or otherwise retaliate against you within six months after you have reported code violations to the code enforcement agency or to the landlord in writing, not only can the landlord not evict you, but you can recover damages from him or her, plus attorneys' fees. If your landlord yells at you, you can hang up the phone or order him or her out of your apartment, and you can call the police. It is illegal for the landlord to shut off utilities or lock you out of the apartment. If you have inadequate heat, others in the building may also. There is strength in numbers.