Social housing is a partial answer to fulfill the demand for low-cost housing and in Europe, there are various forms of social housing that are distinguishable based on whether they employ a universal approach, in which the State guarantees the right to housing and Social Housing acts as a calmer of the market or a residual approach, in which the State intervenes to compensate for market failures.

The latter approach includes national initiatives for social residential building, the financial instrument of which is, in Italy, the Fondo Investimenti per l’Abitare (FIA), a closed-end real estate fund managed by CDP (Cassa Depositi e Prestiti) Investment Sgr, which provides for public and private partnerships. One of the most relevant and critical aspects of social impact investing (SII) operations concerns the measurement of social impact, defined as the portion of the total outcome that occurred as a direct result of the intervention means that not including that part that would have taken place equally without the intervention. Social housing may be traced back to the so-called affordable housing approach. This approach was widespread in Europe, the USA, Canada, and Australia in the 1980s and requires that the satisfaction of housing needs.