The Architecture Today Awards set out to do just that. To exploit the benefit of hindsight. To debate the issue of value in all its messy complexity. We’re asking entrants to join the discussion. To act as advocates, not for their own particular agenda or design, but for the building. To acknowledge its imperfections and the lessons it has to teach us. To define the terms by which it should be judged. To build a case.

The shortlisted projects will be assessed by live presentations; a day of public crits to test and discuss ideas. The debate is what it’s all about. It’s not about picking favourite buildings; it’s about recognising value. A collective effort to focus on what does and doesn’t matter; what does and doesn’t work.

It’s an imprecise, imperfect process. But it’s an attempt to acknowledge the myriad roles that architecture has to play. To grapple with highly complex, hotly contested definitions of architectural value. A moment of collective self-reflection. A chance to re-examine our values within the context of our history and our future. An opportunity to think about the way we build; about how to adapt existing buildings without compromising their value; about whether the decisions we make today will stand the test of time.

What do we value in our buildings? What can hindsight teach us? Who gets to decide? Writing in this issue, Henrietta Billings of SAVE Britain’s Heritage expresses the hope that the impending planning inquiry into plans to raze and rebuild M&S’s flagship Oxford Street store will herald a change in the construction industry, sending out a clear message that demolition should only be considered as a very last resort.

It’s not a new idea. What’s interesting is the collision of different measures of value. Heritage organisations have traditionally defined architectural value in terms of historic interest and aesthetic merit. But they are quickly learning to pitch their arguments in different terms. To talk about the costs – environmental and financial – implicit in demolition. To reiterate the mantra that the greenest building is the one that already exists.

Data on the carbon cost of demolition and rebuilding has become the most valuable weapon in the conservationist’s armoury: readily quantifiable and tricky to contest. It’s a compelling measure of value, but not the only one. It tells us to prioritise existing building stock over building anew. But it doesn’t tell us how to identify more nebulous measures of value: artistic worth; social purpose; historic resonance; civic pride.