We called a few different places, including Mark, when we needed repairs on a system in one of our rentals a few years ago. Mark was the only one who returned our voice mail. He promptly came to the house, explained the problem, gave us options for repair, and professionally and efficiently fixed the problem. We have used him ever since, most recently for an a/c issue. He diagnosed it over the phone, suggested that we check two things, and said if it was neither of those, he could come out the next day. My husband was able to fix the system based on Mark's suggestion. To the people who posted that Mark is a little more expensive, which is not our experience, I would say that his responsiveness, professionalism, helpfulness, and expertise is worth it, especially considering the decline of all of these things in our current economic culture.- Robin D.