He is notable for building the Castle of Antiparos and bringing inhabitants to the island at his own expense.

[1] Apparently the Venetians did not pay much attention to the island which by the beginning of the 15th century was a pirate base and haven.

Loredan brought new inhabitants to the island at his own expense and built the castle in 1440 which had a very specific and unique style of architecture.

The castle and the island remained in the ownership of the House of Loredan until 1480, when they were given as a dowry to Domenico Pisani, son of the Duke of Crete who had married Fiorenza, the daughter of the Duke of Naxos.

[2] Giovanni married Maria Sommaripa (d. 1446), from the family of the rulers of Paros, and they had a daughter Lucrezia Loredan (1446-1528), Lady of Antiparos.