Implied Warranty of Habitability. Talk to a lawyer.

If you told your landlord in writing that the heat and hot water was broken, save copies. If you told him verbally, write down when you told him and what you said as accurately as you can remember. Landlords are required to maintain habitable accommodations, and that includes heat and hot water. If not, you may be "constructively evicted," which means the apartment is uninhabitable to the point where you have to move out and you're not liable for rent (although you should still be saving the rent money in a separate account and not just spending it on other stuff). But talk to a lawyer first, someone already linked phillytenant.org which is a great place to start.