A global attitude adjustment that strongly prioritizes sustainable rehabilitation of our existing resources over new creation, including existing and heritage buildings, is required to meet critical climate change and other environmental targets. This is simply part of the new ‘low-carbon economy’, like recycling programs, car-sharing and similar behaviors. Mid-century modern buildings, by the sheer size of their stock, and their current state of maturation, are a major target, as perhaps the single greatest impact on carbon footprint reduction. There is an urgent need for their necessary large-scale sustainable rehabilitation and deep energy retrofit. Therefore, it is argued, the rehabilitation and rejuvenation of Modern-era buildings and urban systems will very rapidly become the major focus of architectural endeavor over the next few years. This will be one of the foci of the move toward increasing the generally prescribed valuation of our existing resources. Preservation professionals have already developed the skills for adaptation and rehabilitation of existing (heritage) resources while protecting (heritage) value. Therefore, they have the opportunity to be leaders of this coming tidal wave of broader architectural conservation work on Modern-era buildings.