  We demonstrate a micropatterned directional emitter ({\mu}DE) with an
ultrabroadband, azimuthally selective and tailorable emittance across the
thermal wavelengths and over wide angles. The {\mu}DE can enable a novel and
passive seasonal thermoregulation of buildings by reducing summertime
terrestrial radiative heat gain, and wintertime loss. We show several types of
{\mu}DE, such as metallic and white variants, made using low-cost materials and
scalable manufacturing techniques that are already in large-scale use.
Furthermore, we show that its directional emittance can be geometrically
tailored to sky-view factors in different urban scenarios. Outdoor experiments
show that {\mu}DEs stay up to 1.53{\deg}C cooler than traditional building
envelopes when exposed to direct sunlight on summer days and up to 0.46{\deg}C
warmer during winter nights. Additionally, {\mu}DEs demonstrate significant
cooling powers of up to 40 Wm-2 in warm conditions and heating powers of up to
30 Wm-2 in cool conditions, relative to typical building envelopes. Building
energy models show that {\mu}DEs can achieve all-season energy savings similar
to or higher than those of cool roofs. Collectively, our findings show {\mu}DEs
as highly promising for thermoregulating buildings.
