Sam Bowman, Executive Director at the ASI, wrote an article for the Londonist discussing the need to develop more than just brownfield sites, in order to meet the demand for housing in the UK.
At the margin, brownfield can be part of the mix but the idea that it can provide the land for all or even most of our needs is fairly muddled. Brownfield can be costly and sometimes less environmentally friendly to build on than greenfield. Brownfield sites often aren’t in the right places. And the brownfield that is suitable for development is already being developed.