I guess it depends on how long YOU plan to hold these investments. If you plan to get out quickly, then maybe you should worry less. But if you plan to hold until your retirement or something, and that hold date is past 2020 - then I would say it does warrant some concern.
Question, when you say - these requirements were set for 2020 and are impossible - do you mean that the buildings which house people now, would be deemed unlivable, and that would be impossible to get people out and raze the buildings by 2020? or to repair them by 2020 would be impossible?
I'm not sure where in EU you're looking but one angle I would think about is cultural heritage. EU seems to strongly support that, and so if you could make a case at all that these buildings are part of the cultural heritage of your city and as such, can't be torn down, you may not only get a "pass" on certain requirements, you may also be able to get funding help to get them up to code.