[2] A U.S. Army veteran from World War II,[2] he received a Bronze Star Medal and Purple Heart.

[8] He was near Schleiden, Germany in March 1945,[2] repairing a communications line, when a landmine explosion resulted in the loss of his leg.

[13] This method, developed by Pena in the 1960s and published in 1969, had its roots in the post war building boom that was taking place in the United States at the time.

The Problem Seeking method was a means of establishing order and control over a system that had grown increasingly complex during the twenty years following the war.

He promoted the concept of architectural programming where considerations, materials, goals, and a problem statement were formulated by analysts or programmers, which were to be solved by the architects.

[15] It has been defined as "a process that provides the general direction a building's design should take after the client's goals and needs are determined".

[2] He wrote the first edition of Problem Seeking: An architectural programming primer in 1969 with a CRS programmer, John Focke, to document the process.

Its concepts were incorporated into the National Council of Architectural Registration Boards (NCARB) in 1973 and the third edition written with Kevin Kelly and Steven Parshall was published by the American Institute of Architects (AIA) in 1987.

[2] In 1978, the book he co-authored with William Wayne Caudill and Paul Kennon, Architecture and You: How to Experience and Enjoy Building was published.