|1928 Amsterdam||Team competition|
Porenta was born in Ljubljana. He was a member of the Slovenian Sokol athletics movement. With the Yugoslav team, Porenta participated at two Olympic games, at the 1924 Summer Olympics in Paris and in 1928 Summer Olympics in Amsterdam. In Paris, he competed at nine events, his best results being 4th place in men's team competition and 6th place in horse vault. In Amsterdam, where the Yugoslav team won five medals in total, Porenta was a member of the bronze medal winning team at the team competition, together with Edvard Antosiewicz, Stane Derganc, Dragutin Ciotti, Boris Gregorka, Anton Malej, Jože Primožič, and Leon Štukelj.
During the Second World War, Porenta was active in the Liberation Front of the Slovene Nation. In 1942, he was arrested by the forces of Fascist Italy for involvement in the murder of the banker and businessman Avgust Praprotnik (1891–1942) and then shot at the Gramozna Jama ('gravel pit') site in Ljubljana.
- "Janez Porenta Bio, Stats, and Results | Olympics at". Sports-reference.com. Archived from the original on 2020-04-18. Retrieved 2017-02-19.
- Rutar, Miloš (1986). Sodelovati in zmagati: Slovenski športniki v NOB. Ljubljana: Borec. p. 195.
- Križnar, Ivan; Mihevc, Mira (1975). Bitka, kakor življenje dolga: pričevanja o revolucionarnem in osvobodilnem boju Slovencev. Ljubljana: Cankarjeva založba. p. 230.
- "Olympians Who Were Killed or Missing in Action or Died as a Result of War". Sports Reference. Archived from the original on 17 April 2020. Retrieved 24 July 2018.