CLIENT TESTIMONIALS AND PROFESSIONAL REFERENCES

"As a building science expert, I've been following David's comments in the LinkedIn RESNET BPI forum for some time. His articulate, technically savvy commentary is truly insightful. I’m continually amazed at his depth of knowledge in building science, especially HVAC and other building systems. For those of you who think you understand all the intricacies of the building environment, tune in to David’s insightful, thought provoking commentary on a variety of topics you thought you already understood."
Scott Wood, Director of Building Sciences, International Association of Certified Thermographers

"David is one of the top HVAC designers in the country. He has written what is probably the best analysis of the Achilles heel in high performance homes: The Elephant in the Room. Everyone involved with the analysis, construction, or retrofit of homes should read this paper. David 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 on this issue are a great gift to those of us who work in the field."
Allison A. Bailes III, PhD, Energy Vanguard

"Very rarely do you come across someone like David who can apply his vast knowledge to practical situations. This is what separates David from the rest. His unique gift for simplifying the complicated has helped me understand a variety of complex building science principles."
David Richardson, Curriculum Developer and Trainer, National Comfort Institute

"I have known David for over 5 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. Now, 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 has exemplary analytical skills and is one of the few engineers I have met that has a true grasp of building science concepts. I have consulted with David and always find him to be thorough regarding his approach, eager to understand the issue, and very detailed in his solutions and explanation. I enjoy David’s fresh approach to managing building performance solutions."
David Manoguerra, VP National Field Operations, Enalasys Corp

"David was a tremendous asset to our engineering team at Enalasys. If you want it done right, have David look at it first."
Mike Davis, Sr. Director of Product Development & Production, Enalasys Corp

"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, Energy Vanguard

"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.

"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

"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 or remodeling a home. The sooner you get him on board, the better!!"
Keith Sellers, DDS