Which index should I use to index building costs of dwellings?

Statistics Netherlands compiles two series of building costs indices, each with its own uses.
1. New dwellings; input index:
This index includes only the direct costs (wages, materials). This means that changes in fixed general costs and changes in market-related percentages of profit and risk do not affect the index. Therefore this index is ideal for calculating price developments for contracts already agreed.
2. New dwellings; output index:
Unlike the input index, this index does include general costs, profits and risks. This series is used  to index financial plans and estimations for residential construction if no commission has yet been granted. In this way market developments in the construction sector can be taken into account in the financial plans and price quotes.