Client Testimonials

"David is one of the top HVAC designers in the country. He understands the many pitfalls and myths that keep high performance homes from reaching their peak performance. Working with David has shown me that his depth of understanding and leadership in building science and mechanical design are a great gift to those of us who work in the field."
Allison A. Bailes III, PhD, Energy Vanguard

"David's talent, skill and experience puts him in a class of his own for HVAC designers. He can configure any type of system for any location in the most cost-effective way. David has been a great mentor to me as I have developed my skills as a residential HVAC designer. His attention to detail, patience and interest in teaching has been phenomenal. I highly recommend David to any homeowner or builder looking for the best HVAC system."
Chris Laumer-Giddens, Architect/HERS Rater/HVAC Designer/LEED AP, LG Squared, Inc.

"After reading David's article in the Sept.'09 issue of Home Energy, I knew he had the knowledge to assist Sun Plans with HVAC for the low-energy, passive solar homes we design for clients throughout the country. In a recent project, the services David provided Sun Plans, the homeowner, the HVAC contractor, the builder, and the insulation contractor proved invaluable. The fee for his advice and specifications paid for itself immediately in reduced costs for the project, and will continue to pay back over the years with reduced energy bills. We look forward to working with David on future low-energy homes."
Debbie Coleman, Architect, Sun Plans Inc.

"I have known David for over 9 years. While I was working as a Home Energy Rater with David, we worked on several complex home designs and I came to rely on his thorough knowledge of HVAC systems. As a home builder, I only trust David to do the load calculations on every home I build. His expertise is invaluable to me as a rater and as a builder."
Jessica Oakley, Oakley Custom Homes

"David Butler of Optimal Building Systems provides a service that is essential in properly designing a new home with today's "tight home" technologies. His thorough approach and overwhelming knowledge put him in an ideal position to design heating and cooling systems that maximize efficiency at the lowest possible cost."
Bryan Gerrard, Gerrard Homes

"After occupying our newly built high performance home, we realized the HVAC system was not designed properly and a severe moisture problem was imminent. So I contracted David to evaluate our situation, and to design and specify the optimal HVAC equipment for our home. All four mechanical systems needed to be replaced. David's engineering expertise is exceptional. He would not be satisfied until every aspect of his design was confirmed. David's confidence and attention to detail is comforting and we couldn't be happier with the end result. With pleasure, we gladly recommend David to others."
Steve & Sheryl Simonton

"I cannot say enough good things about David! I brought him on board to optimize the HVAC design for our indoor swimming pool, as well as the geothermal domestic hot water system for our new home. I was extremely impressed with his knowledge and his thorough and detailed recommendations, which were extremely well researched and analyzed. His proposed solutions were clear and balanced. It's refreshing to find someone who takes costs seriously and not get carried away by technology for technology's sake."
B. Ramkumar

"As homeowners trying to build a one-of-a-kind high-performance passive solar home in rural Oklahoma, we were overwhelmed by differing opinions as to the appropriate size for our HVAC system. We brought in David Butler of Optimal Building Systems to provide independent specifications for our HVAC system. His expertise was invaluable in helping us make critical decisions on our HVAC system. We highly recommend him to others in this situation."
Bill & Janet Williamsen

"David Butler was extremely instrumental in designing an effective and efficient "green" home for us. His knowledge of all building systems was beneficial and cost-saving for us, especially the HVAC and hot water systems. I would highly recommend David to anyone building a new home. The sooner you get him on board, the better!!"
Keith Sellers, DDS