In Pennsylvania, does an email declaring an intent to renew a lease constitute a legally binding agreement.

This is one of those "it depends" situations. First you need to turn to the lease itself to determine what its notice requriements are and what steps are required for it to renew. Some leases renew automatically for an additional term that is as long as the original term. Others become month-to-month, terminable on one month's notice; and others terminate absolutely at the end of the term and you become a "holdover" tenant, which opperates much like month-to-month alternative. As to notice, even if written notice is required, there are many instances where an email will be sufficient, but that is not an absolute. It would be very wise for you to contact an experienced real estate attorney to review this for you and let you know what your options are. I am assuming this is a residential consumer lease, so you do have legal protections your landlord may be ignoring. By the way, why didn't you execute the lease renewal addendum when it was first presented to you?

I agree that the answer depends on several factors...not only other terms of the lease but facts and circumstances which have nothing to do with the written terms of the lease but more about the intentions of the parties etc. It would be best if you consulted with a real estate attorney and explained everything that happened and show them a copy of the lease and any other written correspondence between the parties (including emails and texts).