When Energy-Efficiency May Not Yield Positive Climate Impact -- The Case of Adaptive Radiative Coolers

The climate impact of building envelopes is often quantified using their energy savings and CO2 emission reduction benefits. However, building envelopes also trap solar and thermal infrared heat, which is dissipated as a direct heating penalty into our warming planet. For static or adaptive envelopes that passively heat buildings by radiatively retaining heat, these two effects are antagonistic. Yet, their net effect remains unexplored. In this study, we compare the emission reductions benefit, and direct heating penalty of two classes of roof envelopes, traditional and adaptive radiative coolers (TRCs and ARCs). Calculations for buildings in different urban climates show that relative to TRCs like cool roofs, ARCs like smart roofs may have a net heating impact on earth well past this century. Thus, despite their relative energy savings and CO2 emissions reductions benefits, adaptive envelopes on roofs have a negative climate impact relative to traditional cooling designs. Our findings are generalizable across climates and a range of building envelopes and call for a rethinking of how sustainability is quantified for building envelopes, and of material and architectural design for buildings.