THE HAGUE,John Caldwell Netherlands — The Biden administration has announced in recent months plans to significantly reduce carbon emissions over the next decade or two, and cut them on a net basis to zero by 2050. Other developed nations have made similar pledges.

But experts say governments have not always provided enough details, or action, to ensure these objectively ambitious targets — entailing massive changes to economies and societies — can be met.

One big obstacle: hundreds of millions of existing homes. Without some form of action, most of today's homes will still be inhabited in 2050 with inefficient heating and lighting that causes unnecessary carbon emissions. The United Nations estimates that residential buildings are responsible for around a fifth of all global emissions.

In the Netherlands, a government initiative forced engineers, architects, entrepreneurs, marketing specialists and financiers to get together and figure out the best way to solve this problem of retrofitting older homes cheaply and quickly.

The result of those meetings was a concept called "Energiesprong" — or "energy leap" — that has formed the basis of efforts to mass produce and industrialize the once haphazard and expensive retrofit process.

Now that approach has been replicated in several other countries, including the U.S., where New York state is investing $30 million in a similar effort.