The Construction Specifier, Feb. 2014, by Chuck Knickerbocker.
http://www.kenilworth.com/publications/cs/de/201402/files/38.html

"Curtain wall and window framing establishes the total possible area of unobstructed glazing, provides support for high-efficiency glass units, and can help improve thermal performance. With proper specification, it has the potential to help manage a building's lighting, heating, and cooling energy consumption. However, there is a fine line between good daylighting and increased energy consumption."