The impact of the increasing technomass (TM) on cooling demand in buildings is explored for cities in South America. The entangled double nature of the building–environment interrelation in an urban context is analyzed. The research question is whether an increase in the building density produces a superlinear increase of energy consumption at the urban scale. Advanced spatially explicit quantitative methods are used to select representative samples of the urban environment and to quantify the volumes of TM in four South American cities. Principal component analysis is used to extract representative urban tissue categories. The Urban Weather Generator tool is used to produce the urban weather data used in building performance simulations. The results confirm the superlinear dependence of the total cooling consumption of each sample in relation to the existing TM in areas with high-rise buildings due to the combined primary and secondary effects, namely, the increase of the total energy needs and the increase of air temperature due to the urban heat island effect. The great significance of the second-order effect poses challenges to current assessments performed on the basis of consumption per m2. The use of the TM indicator can promote the development of climate-sensible urban planning.