This paper applies the Rational Exergy Management Model (REMM) to evaluate sustainable cooling strategies for low-exergy green buildings and green cities, mimicking ecosystems that utilize exergy more optimally. The paper includes a special formulation of the exergy demand for space cooling and a definition of an effective temperature of solar insolation based on a technique of exergy-mapping. The alternatives to a base case as characterized by structural exergy overshoots and high avoidable CO2 emissions impacts include absorption cooling with renewable energies for district cooling in high-density areas. A new, REMM guided built environment signature is also provided to monitor transformations towards a foresight for a built ecosystem. The paper concludes that there must be significant progress for more optimal linkages in the exergy supply and exergy demand points to minimize CO2 emissions impacts.