Heating, Ventilation and Air-Conditioning engineers face high demands from their clients to deliver reliable, optimized solutions that perform acceptably in terms of energy use and provided comfort. However, time and resources are scarce to deliver an optimized solution. To ensure that the solution works under most operation scenarios, the design is typically based on a combination of conservative rules-of-thumb, general guidelines and a large safety factor. The consequences are building service systems designed for operating conditions that never or very rarely occur leading to oversized systems. The objective of this paper was to propose a method for identifying oversized air-handling units with variable speed drives. It was demonstrated on a case study including six air-handling units in an office building. The method was able to determine that the air-handling units were not grossly oversized or undersized by comparing the measured airflow and SFP from the part- and full-load operation to the design airflow and SFP. However, the method should be extended to include additional performance criterion such as indoor climate and thermal efficiency to be able to conclusively confirm the size of the units.
Monitoring performance of heating, ventilation and air-conditioning (HVAC) during building operation enables to evaluate the appropriateness of the system's design. Such insights can help to reduce energy consumption while ensuring satisfying indoor conditions in the monitored building. Additionally, such insight can help to improve future HVAC design. The aim of this paper is to present a case study demonstrating how HVAC engineers can evaluate whether the monitored air-handling units (AHUs) were appropriately sized and performed as intended based on design requirements regarding energy-efficiency, thermal conditions and indoor air quality (IAQ). Three months of measurements of airflow, electrical power, indoor temperature and CO 2 -concentrations were collected from an office building with six AHUs. The results showed that three of the AHUs were appropriately sized and satisfied the thermal condition, IAQ and energy-efficiency requirements. The remaining three AHUs were apparently appropriately sized and satisfied IAQ requirements, but they did not satisfy the required energy-efficiency and thermal conditions. The applied approach seemed to be suitable for supporting building operating managers for on-going performance monitoring as it was able to identify discrepancies from intended performance. But it remains the task for the operating personnel to identify the cause of the identified discrepancies.
Occupants can provide valuable feedback on the indoor environmental quality of buildings. Research on occupant voting systems (OVS) has demonstrated that apps or electronic devices can act as viable tools for collecting long-term feedback from occupants. However, previous research has only to a limited extent explored occupants’ interaction with OVS and the impact it might have on the reliability of the collected feedback. The present paper presents three case studies on applying a tangible OVS, denoted TiAQ, to collect feedback on thermal and indoor air quality (IAQ) in office spaces. The main objective of the present study was first to explore occupants’ interaction with TiAQ and their motivation. Second, identifying whether feedback collected with TiAQ could represent occupants’ comfort and discomfort with the thermal environment and IAQ. Thirdly, identifying challenges related to occupants’ interaction with TiAQ that might affect the representativeness of collected feedback. The present study was conducted at three office buildings in up to 7 months and demonstrated that TiAQ was suitable for collecting long-term feedback on occupants’ comfort and discomfort with the thermal environment. On average, one vote was cast per day per occupant. Additionally, in one of the office buildings, 60% of occupants reported to have interacted with TiAQ daily or weekly when, e.g., passing the device going to/from the office spaces. Occupants’ expectations of TiAQ and getting “feedback on feedback” need to be further addressed to identify ways to sustain occupants’ long-term use of the device and reduce “ill-willed” interactions.
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