According to the Pennsylvania Home Improvement Law, effective as of July 1, 2009, the Licensed Contractor, Christian Heating and Air Conditioning, Inc., shall not perform any home improvement project where the contractor will be paid $500 or more without a written contract signed by the contractor and the owner.  However, it can be completed if it is for an emergency or the homeowner has waived their 3-Day Right of Rescission Act.    
This applies to many other types of Home Improvement work and you can call the toll free number at anytime (1-800-520-6680) to see if your contractor is a licensed professional or look for it on a contractors advertisement, website, contract, vehicles, etc. which should start with the letters PA00 then the contractor's number. Christian Heating and Air Conditioning, Inc’s contractor number is PA004411. 
  • Pennslyvania Home Improvement Consumer Protection Act
  • 3 Day Right of Rescission
  • PA Attorney General Site