I'd like to repeat my stance that no social housing should be located in the city centre.
If you are trying to maximise the economic use of land perhaps it would be better to focus on building on public parks? No? But it's ok to force the elderly or ill out of their communities?
All communities need social housing and it serves it's purpose best when it's prevented form becoming marginalised ghettos. We know that.
It depends whether you think social housing should just be for people who can't/ won't work.
In my opinion social housing is not just for those who are out of the workforce.
At the very least social housing should also be provided when the private sector does not provide - that is the current issue. If the State is using bed and breakfasts and temporary accommodation then the private sector is not providing housing for these people. It is much more economic for the state to provide housing in this case. That's the easiest case to justify - it has a sound economic basis. We have been using this type of accommodation for a long time - we would have saved money by providing social housing.
Where housing is not affordable (either to rent or to buy) for the working poor the state also has an issue as we obviously have a shortage of housing. In this case social housing can act as a buffer for supply. The state also has an issue as it will not be able to attract key workers to work in areas of expensive housing without raising pay. The old council house scheme was simple - you built good quality houses and charged rent at a rate people could afford. You raised the rent if their economic circumstances changed and over the years you hoped that you would get back the initial capital cost from the rents received (I'd be interested in Dublin City Councils return on their initial capital outlay). There is an issue about this approach - if someone becomes very wealthy how do you move them out of their house and their community (kids schools etc)? This is why you try to spread social housing around the city. And you stick close to the city because most of the work is there and if you have a low income there's a good chance you can't afford to run a car and we all know about Dublin public transport. The justification of this case is partly a matter of political belief but perhaps people forget how social housing happened in the UK - after the war no business had sufficient capital to invest in the replacement of the housing that had been bombed - only the state had the means and it had the will as well as men had returned from the war with no jobs - social housing resolved this issue.
In the case of Ireland developers were restricted in access to capital after the crash so no building was done, we also had a surplus of construction labour and large landholdings in the hands of the state. There was a huge opportunity at this stage - missed partly because of a conflict of state interest (the state wanted the highest price for the land) and partly by a desire not to borrow. A few years later Europe began chucking money around but for some reason no one asked if we could have used it to build social housing - money pumped into the economy at this level would have had a multiplier effect - as we know house building can have an enormous economic stimulus - it is mainly spent locally, we would also have reduced unemployment. Instead the money fed yet another round of housing speculation. By having this pool of social housing we would have a buffer against wild fluctuations in the price of housing - instead we've gone back to boom and bust.