This is something I’ve been wondering. Say you have an apartment building that is several decades old, would it be better sustainability wise to try and make the old building greener or tear it down and rebuild it? Tearing it down and rebuilding would require a lot more resources and potentially energy than retrofitting, but a new building would have better insulation whereas an old building would likely be straight brick or concrete, more efficient HVAC systems, and usually have units that are physically smaller so more units and therefore people would be able to fit in the same size building (though that last point is definitely more due to capitalism than environmentalism, due to rising real estate prices). I also imagine you can’t really retrofit more advanced green features like grey water recycling, advanced HVAC systems, etc without so much effort that it would approximately equal the resource consumption of rebuilding, I’d love to be wrong though. Does anyone have any experience or research on which option would be better?
I think it depends on the age of the building and what condition it’s in. A very specific building instance I know of is schools. Many schools built in the past 30 years are already falling apart, but schools built earlier than that are often far more stable and still standing with general upkeep. If the building is newer, I’d say just redo it since the lifespan is pretty short, but for older buildings it’s probably better to attempt updating it. Putting insulation in older buildings is work, but if the exterior structure is fine then it will last.