Assessing the long-term energy performance of automated interior insulating window shades in a high-rise commercial building

Abstract

This study evaluated the HVAC energy end-use performance of 39 motorized insulating interior shades installed on the 37th floor of a high-rise commercial building in Chicago, Illinois, USA operating under realistic conditions. The study lasted for 44 weeks (spanning all four seasons). Three motorized control strategies of On-schedule, Dynamic (‘smart’), and Manual, as well as one typical mini-blind Baseline control strategy, were developed and implemented to assess energy performance of the interior automated shades. The three controlled motorized control strategies are compared to the Baseline strategy as a reference. The results showed that the motorized interior insulating shades reduced daily energy consumption by up to 20.5 % with the automated control strategy, which includes the Dynamic and On-schedule strategies, and up to 11.8 % without the control, which includes only the Manual control strategy. A weather normalized energy consumption analysis, which translates the actual energy consumption values to typical year energy consumption values, indicates that the automated shades are expected to save 20–35 % in energy consumption compared to the Baseline strategy. The calculated payback period for a defined “best practice” scenario is 21.9 years considering an initial electricity rate of $0.0897/kWh in 2021. Accounting for a future utility incentive program that provides a one-time rebate of $0.25/kWh savings during the installation, the simple payback period for the “best practice” scenario was estimated to be 12.3 years with the 2021 electricity rate and 4.4 years with assumptions for future electricity rates. Results suggest that the shades are a promising energy efficiency measure, especially for buildings for which building envelope retrofits or new construction are cost prohibitive or infeasible.