What buildings do you think are especially good at forging a balance between the individual and the collective? Two that I think of are Herman Hertzberger’s Apollo School and the Pike Place Market.
The configuration of the Hertzberger’s Montessori school allows for gathering spaces at multiple scales, from a small group of children to an entire class with teacher, as well as providing multiple spaces for single students to retreat from the group. The balance is achieved because neither type of space dominates the building. Also, the spaces of different size are arranged so that an easy transition between space for the individual and that for the collective is achieved, further enhancing the balance.
The architecture of the Pike Place Market in Seattle balances the individual and collective in a slightly different way. At the Market, the spaces are designed for the individual craftsmen and farmers to have autonomy and a sense for ownership over a space, a space that is often temporary. Together, these fairly anonymous spaces form a whole that serves the collective. For example, while the individual vendors may vary from day to day, the areas in which they set up generally have the same type of goods. The individual is accommodated, but only as part of a collective whole. This is enhanced by the design of the stalls themselves, which are partitioned for each, but connected together for the collective vendors.
There are certainly a lot of environmentally sustainable buildings that could work harder at being socially sustainable and this individual/collective balance is "low-hanging fruit", like adding fly ash to concrete.