I am an engineer and scientist who is both interested in every aspect of a service I have engaged, and demanding too. I am typically knowledgeable in many, but not all, facets of work that is done for me. Many vendors would steer away and become defensive when I proffer too many detailed questions, but not R&D HVAC. Brian McNeil answered all my questions and accomodated my unusual requests with a collaborative exchange of information. Our new-construction two-zone HVAC system was installed promptly, professionally, and with the highest standard of workmanship. It has been a pleasure dealing with R&D HVAC. I will call on them again.