Das had laid the foundation stone of the building on June 12, 2015.
The three-storey building has been constructed at a cost of Rs 465 crore. Prime Minister Narendra Modi inaugurated the building in the presence of Governor Droupadi Murmu and Das on September 12 this year. The new building is paperless.
Das was on Monday defeated in his bastion, Jamshedpur East, by his independent rival and former Cabinet colleague Saryu Roy by a margin of 15,833 votes.
Das, who had held the seat since 1995 when it was in undivided Bihar, secured 58,112 votes while Roy got 73,945 of the total 173,618 votes.
Congress candidate Gourav Vallabh came third with 18,976 votes.
Das, who had mostly been trailing in the seat since the counting of votes in the five phase Assembly election began on Monday morning, had also asserted the BJP would return to power even as early trends showed the Jharkhand Mukti Morcha-Congress-Rashtriya Janata Dal alliance maintaining a good lead.
The alliance eventually won 47 seats in the 81-member house, while the BJP was reduced to 25 seats, against the 37 it won in 2014.
Former minister Roy, whose efforts put two former Chief Ministers Lalu Prasad and Madhu Koda in jail for corruption, had given a tough fight to Das, in an unprecedented trend which was not expected by the Bharatiya Janata Party (BJP) that had put on hold Roy's ticket from Jamshedpur West, leading him to resign from the Ministry and Assembly and confront Das.
After facing a humiliating defeat Das owned the responsibility for the loss. As he has lost the Assembly polls he will not be able to take part in the Assembly Session till 2024.
( With inputs from IANS )