Building America Solution Center
Provided by the US Department of Energy. Looks like a tremendous resource.
"The Building America Solution Center provides access to expert information on hundreds of high-performance construction topics, including air sealing and insulation, HVAC components, windows, indoor air quality, and much more. Click on the links below to explore the Solution Center."
Here you will find a collection of material, ranging from technical data to white papers to theory, which has influenced my thinking.