An interesting approach to speeding up the retrofit of existing buildings is to set limits on carbon emissions for individual buildings in cities:
In just the past 18 months, the trend has taken off, from Washington, D.C. to New York City to Washington state to St. Louis, where the mayor signed a plan into law just last month.
The plans, known as building performance standards, require buildings larger than a certain size to meet an energy efficiency standard, based on either how much carbon they emit or how much energy they use.
There are countless ways building owners can improve energy efficiency, including better sealing of gaps to the outdoors, replacing old HVAC systems, upgrading lighting, and installing smart energy management systems.