Loeffel was named to Switzerland's national under-18 team for the 2008 IIHF World U18 Championships in Russia. He tallied 1 assist in 6 games, with Switzerland finishing 8th in the tournament. Loeffel was again named to the team for the 2009 IIHF World U18 Championships in the United States where he put up 4 assists in 6 games, finishing again 8th in the tournament with Switzerland. That same year he was also named to Switzerland's under-20 team for the 2009 World Junior Ice Hockey Championships – Division I in Switzerland. He played 5 games to help Switzerland win the tournament and earn a promotion for the 2010 World Junior Ice Hockey Championships in which he did not participate, but was selected to take part in the 2011 edition in the United States. Loeffel scored 1 goal, helping Switzerland finishing 5th in that tournament.