Think about that question for a moment. What features would the greenest building have?. A super-efficient envelope? The most advanced digital controls? A groundbreaking automation system? Does it take daylighting principles to a new level? And how recently do you think the building was completed? Maybe within the last three years?
In fact, the greenest building may be the old building that you are managing and occupying right now, albeit with some carefully considered updates for its continued use.
This answer is based on the concept of avoided environmental impact, and from that perspective, things look quite different than we typically see them. The Greenest Building: Quantifying the Environmental Value of Reuse, a research report from the National Trust for Historic Preservation, shows how the built environment looks from this vantage point.
There are many factors and variables in the research, but it can be summed up by this generalization: If a new building operates at 30% greater efficiency than an existing building, it will take anywhere from 10 to 80 years for the new building’s greater efficiency to overcome the climate-change impact of its construction and possible demolition of an old building.
There are numerous caveats, of course. Climate is a variable: A new commercial office building in Chicago would have a 25-year environmental payback, whereas the same building in Portland would need 42 years. That projection is partly based on another variable, which is the mix of fuel sources used to generate electrical power in different regions. Building type is another factor: a new multifamily building in Chicago or Portland has a significantly quicker payback, at 16 and 20 years respectively, than the new office building in those cities.
On the reuse side of the equation are also many caveats. For example, the environmental benefits of reusing a building can be reduced to zero by poor choices in the quantity and type of materials used. And for some reuse projects – such as conversions from warehouse to residential – the environmental payback may be never. The amount and types of materials used in these conversions are greater than those of other reuse scenarios and thus likely to negate the climate change advantage.
We have a deep bias toward new buildings, an attitude that is embodied in building codes, performance standards, and our expectations. The regulatory and financial infrastructure of facilities would need to change if avoided environmental impact becomes a priority. It is also fascinating to think about the new technology and solutions that would be developed for reuse.
The report is thought-provoking and suggests an area that should receive more research. You will find it at the National Trust’s website: www.preservationnation.org.