Key questions to ask when looking for a qualified HVAC contractor:
Is the contractor licensed by the state? Many states have websites listing the contractors and the licenses they hold. In California for example, homeowners can check online at http://www.cslb.ca.gov.
Does the contractor have the right license for the work being performed?
Is the contractor a certified member of a professional organization? To obtain the designation as "NATE (North American Technician Excellence) Certified," for example, contractors must pass a rigorous test.
Did the contractor provide references, and have you solicited proposals to compare not only the cost but the specific work to be performed and the materials used?
Is the contractor fully insured and bonded? This includes workers compensation insurance and general liability insurance for damage to your home or injury to the homeowner or the contractor's employees.