I've had the privilege of working numerous conferences with John and a few RPA gigs under the banner of "Siggy and the Bean". Siggy is in a league of his own when it comes to engineering.  I just finished a review of his Heat Load Estimator for HPAC Magazine and reviewed for the same publication, his text Modern Hydronics which remains industry's most authoritative, informative, and reliable manual on hydronics. In addition his course material for educational institutes and industry organizations are the benchmark for learning about application and design as are his magazine articles. Read a sample of John's writings on such topics as Bubble Foil Insulation. 

Here is a bit of background from John's website:

Appropriate Designs was formed in 1983 by John Siegenthaler, P.E., to provide engineering design services specifically focused on low-energy-use buildings. Specialties include solar energy applications, super-insulated construction, and hydronic heating. Today the company focuses solely on state-of-the-art application of hydronic heating. Through extensive research and application of engineering principles, Appropriate Designs has developed advanced modeling methods for simulating the thermal and hydraulic performance of hydronic systems. These models have been used to develop software-based sizing and selection programs for several manufacturers, as well as numerous publications, and training seminars.

So that's what the guys at Appropriate Designs are about. John's also got some gents working with him on application and design software. Mario Restive and Anthony Macera are both engineering grads with computer science backgrounds. Together with John they have created some very useful and practical software packages which every designer should have.
 

Last but not least...

I always love reading a company's raison d’etre and this is their's...

Appropriate Designs will continually advance the science and proper application of hydronic heating through development of advanced support materials including engineering models, software, publications, training seminars, and system design consultation.

Be sure to add these gentlemen to your list of resources.

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