TY - JOUR

T1 - Can Areawide Building Retrofitting Affect the Urban Microclimate? An LES Study for Berlin, Germany

AU - Maronga, Björn

AU - Winkler, Matthias

AU - Li, Dan

N1 - Funding Information: Acknowledgments. Author Li acknowledges support from the U.S. National Science Foundation (Grant ICER-1854706) and the U.S. Army Research Office (Grant W911NF-18-1-0360). Simulations were carried out on the computer clusters of the North-German Supercomputing Alliance (HLRN).

PY - 2022/7

Y1 - 2022/7

N2 - In this work, we investigate the effect of areawide building retrofitting on summertime, street-level outdoor temperatures in an urban district in Berlin, Germany. We perform two building-resolving, weeklong large-eddy simula-tions: one with nonretrofitted buildings and the other with retrofitted buildings in the entire domain to meet today’s energy efficiency standards. The comparison of the two simulations reveals that the mean outdoor temperatures are higher with retrofitted buildings during daytime conditions. This behavior is caused by the much smaller inertia of the outermost roof/ wall layer in the retrofitting case, which is thermally decoupled from the inner roof/wall layers by an insulation layer. As a result, the outermost layer heats up more rigorously during the daytime, leading to increased sensible heat fluxes into the atmosphere. During the nighttime, the outermost layer’s temperature drops down faster, resulting in cooling of the atmo-sphere. However, as the simulation progresses, the cooling effect becomes smaller and the warming effect becomes larger. After 1 week, we find the mean temperatures to be 4 K higher during the daytime while the cooling effects become negligible.

AB - In this work, we investigate the effect of areawide building retrofitting on summertime, street-level outdoor temperatures in an urban district in Berlin, Germany. We perform two building-resolving, weeklong large-eddy simula-tions: one with nonretrofitted buildings and the other with retrofitted buildings in the entire domain to meet today’s energy efficiency standards. The comparison of the two simulations reveals that the mean outdoor temperatures are higher with retrofitted buildings during daytime conditions. This behavior is caused by the much smaller inertia of the outermost roof/ wall layer in the retrofitting case, which is thermally decoupled from the inner roof/wall layers by an insulation layer. As a result, the outermost layer heats up more rigorously during the daytime, leading to increased sensible heat fluxes into the atmosphere. During the nighttime, the outermost layer’s temperature drops down faster, resulting in cooling of the atmo-sphere. However, as the simulation progresses, the cooling effect becomes smaller and the warming effect becomes larger. After 1 week, we find the mean temperatures to be 4 K higher during the daytime while the cooling effects become negligible.

KW - Adaptation

KW - Atmosphere–land interaction

KW - Boundary layer

KW - Heat islands

KW - Large-eddy simulations

KW - Urban meteorology

UR - http://www.scopus.com/inward/record.url?scp=85134028555&partnerID=8YFLogxK

U2 - 10.1175/JAMC-D-21-0216.1

DO - 10.1175/JAMC-D-21-0216.1

M3 - Article

AN - SCOPUS:85134028555

VL - 61

SP - 800

EP - 817

JO - Journal of Applied Meteorology and Climatology

JF - Journal of Applied Meteorology and Climatology

SN - 1558-8424

IS - 7

ER -