Exterior greenery systems such as green walls and green roof can provide energy saving and environmental benefits. Several previous studies examined thermal impacts of green roof/walls on a test envelope or simplified buildings in local climates. However, few studies examined the effects of exterior greenery systems considering building types, air conditioning operating conditions, and wall orientations in varied climates. The objective of this study is to investigate cooling energy savings associated with exterior greenery systems for the US Department of Energy (DOE) standard reference buildings, depending on building type, wall orientation, and local climate. Hourly energy consumption was examined for three types of reference buildings: (1) medium office, (2) hospital, and (3) primary school. For the three reference buildings, hourly solar radiation and latent heat transfer rates were calculated for four representative local climates (i.e., hot-dry, hot-humid, cold-humid, and warm-dry). Results show that latent heat transfer due to plant transpiration can dominate heat transfer through the exterior greenery systems. Among the four climates studied herein, heat removal due to evaporation by green walls and roof over the summer months (June to August) is the largest (up to 680 kWh/m²) in Phoenix, while it is in similar range (300–350 kWh/m²) for green walls and roof in other cities. Building type also has notable impacts on the energy performance of the exterior greenery system. Primary school achieves the most significant cooling energy saving in all climates because of high envelope heat gains compared to medium office and hospital. For the primary school in Phoenix, annual cooling energy saving can be maximized up to 27,000 kWh/y with green walls and up to 69,000 kWh/y with a green roof. Latent heat transfer due to evaporation is similar (< 6%) between south and west green walls, implying that utilizing a west green wall could be a good alternative or complement to using a south green wall for cooling energy saving.

Large variation in indoor air quality (IAQ) and thermal comfort can occur in partitioned office spaces due to heterogeneous air mixing. However, few published studies examined IAQ, thermal comfort, and energy performance of partitioned occupied spaces, which are commonly found in today’s buildings. The objective of this study is to evaluate indoor environmental quality and air conditioning performance of a partitioned room under two typical ventilation modes: (1) mixing ventilation and (2) displacement ventilation. For a total of six representative air-conditioning scenarios, three-dimensional computational fluid dynamics (CFD) simulations are performed to examine temperature distribution, ventilation effectiveness, energy consumption, and local thermal comfort for two partitioned spaces. Simulation results indicate that temperature distribution in a partitioned room is a strong function of ventilation strategy (mixing vs. displacement), but marginally affected by diffuser arrangements. Local age-of-air (air freshness) significantly varies with both diffuser arrangement and ventilation strategy. Regarding energy consumption, displacement ventilation can achieve an indoor set-point temperature in the partitioned spaces about two times faster than mixing ventilation. Under mixing ventilation, the time to achieve a set-point temperature was notably reduced when each partitioned space is served by its own diffuser. For the same supply airflow rate, displacement ventilation can generate local draft risk at ankle level, while mixing ventilation may result in a draft sensation in wider areas around an occupant. Overall, the results suggest that mixing ventilation system can save energy if each partitioned zone is served by its own diffuser such as a multi-split air conditioning. However, when multiple partitioned zones are served by only one diffuser, displacement ventilation is more energy-efficient and can achieve higher ventilation effectiveness than mixing ventilation.