In the fields of energy and environment, I have seen paradigm shifts take place on several important occasions during my career. Paradigm shifts dramatically change the conversation about how to deal with problems. For example, economists have recognized the concept of externalities since the 19th century…

Where did our current thinking about paradigm shifts originate? In the 1960s, MIT Professor Jay Forrester created a field called system dynamics by modeling how industrial production systems behaved in response to fluctuating demand. He wrote Urban Dynamics, which attempted for the first time to describe how more complex systems like cities behaved and could be modeled. He and his team created models used by the Club of Rome to research its highly influential 1972 book, The Limits to Growth.

In 1927 the Jesuit scholar Pierre Teilhard de Chardin postulated the existence of a global “mind,” a noösphere, connecting everyone and everything in the world. By 2017 there were about two billion Facebook users, more than a quarter of earth’s population. The paradigm shift that connects everyone on Earth, all the time, everywhere, less than one generation ago a fanciful dream, is now our daily experience.

Mental models are the primary tools we use to think about creating a more sustainable future, for example, but are they accurate or even useful? For example, will replacing gasoline-powered cars with electric cars lead to a truly sustainable future, if there are still a billion cars in the world and the electricity to charge them comes from fossil fuels? What are the paradigm shifts that created green building as we know it today?

At the beginning, LEED certification met a market need and grew dramatically. Within a half-decade after its introduction, by 2006 LEED was a well recognized brand and globally known “eco-label,” a remarkable achievement. But LEED could never guarantee that buildings it certified were among the top 25 percent of all performers, its stated goal, as measured against key criteria for reducing environmental impact.

Here is a critical dilemma for the environmental movement. If we want to preserve this beautiful planet from the ravages of global climate change, we must insist that every “solution” offered by well meaning organizations agrees to real-world independent testing.

Green building has a significant credibility problem. While the world is awash in green building "eco-labels" and while these have significant credibility in the commercial building marketplace, conspicuously missing are any serious studies of the actual performance of green buildings. This issue has been highlighted since at least 2010, but none of the leading green building councils has yet to commission such a study.

What is the real contribution of LEED buildings to reducing US greenhouse gas emissions? Some recent tweets cite a 2011 study that estimates nearly a 2% reduction by 2020. In my analysis, the actual number is more like 0.3%, only about one-sixth of the projection from six years ago. This makes LEED (and to some degree green building) far less important than many of us had assumed. Take a look, decide for yourself and let me know what you think!

Are Zero Net Energy (ZNE) buildings technically feasible in the United States? A recent article by Charles Eley casts doubt on the goal of making all new buildings "zero net" with onsite solar by 2030 and all buildings, new and old, by 2050. Our best bet for the buildings sector is utility-scale solar and wind power, coupled with "ultra low energy" new buildings AND massive retrofits of existing buildings.

Should we adopt a goal of ALL BUILDINGS net zero energy by 2050, as advocated by the World Green Building Council? Wouldn't it be far cheaper, faster and more feasible instead to focus on 100% renewable energy for entire countries by 2050? That would make all buildings effectively "net zero," wouldn't it?

Big news last week: A USGBC press release reported a new academic study that shows that LEED-certified homes in Texas sell for 8% more, equivalent to about $25,000, and that all “green-certified” homes sell for a 6% premium, equivalent to about $19,000 more. Turns out, there’s more than a few shades of gray to the conclusions in the report.