Methodology for the Evaluation of Natural Ventilation in ... - Cham

Finally, airflow visualization was included as part of the assessment of the building to improveunderstanding of the characteristics of natural ventilation in the building design. Smoke pencilswere used for localized flow patterns throughout the building. These experiments proved to beuseful supplemental information in determining the airflow paths at the inlet conditions, withinthe occupied space and atrium, and at the exhaust, but cannot be quantified reliably outside oflaboratory conditions. Another method with ‗neutrally buoyant‘ helium balloons was used totrack the airflow patterns within the building. The neutrally buoyant balloons were made neutralat a selected height, which corresponded with a specific temperature. When the balloon wouldmove to an area of a different temperature, it would oscillate until reaching the neutraltemperature again (Glicksman 2004). The balloons were then released near the inlet windows,and allowed to travel within the building. The balloons normally ended up near the roof of theatrium, the warmest location within the building. However, this method did not producerepeatable results for specific streamlines. The balloons were able to follow larger, macroscopicflow patterns within the space, but had difficulty with low velocity airflow and detailed flowpatterns visible using the smoke pencils.3.3.1.3 Energy UsageThe occupancy schedule and energy usage profile can be determined by monitoring the energyconsumption and usage patterns within a building. The more detailed the metering of the electricenergy using equipment, the more thorough is the understanding of the building energyperformance. For the prototype building, not only the overall energy usage, but also a substantialamount of detailed monitoring was completed. This detailed monitoring included data collectionon each floor level by orientation, miscellaneous building services, lifts, atrium fans andexternal/outside lights to determine their energy consumption. The energy usage for each floorcould not be separated out in more detail, e.g. lights versus plug loads, due to problems withinstallation of the data loggers in the electrical closets. Current transducers (CTs) were alsoinstalled on the actuators for the boiler so that there was a measure of how often the boilers werein operation and their schedule of operation. Enernet K-20 electric energy data loggers wereinstalled along with CTs of various sizes ranging from 50 amps to 500 amps to capture energyusage data. CTs were installed on each of the three phases for each sub-system. Though the datawere recorded over the eighteen-month period, there was still a 10 percent margin of errorbetween the monitored data and the monthly energy bills. Since there were a limited number oflocations to install the K-20s, it is assumed that not every load was measured. Additionally, thetotal energy consumption was not recorded due to the limitation in size of CTs available and thelocation of the incoming power supply. As a validation for the recorded data, energy usingequipment and systems were inventoried by a walk-through assessment of Houghton Hall forcomparison.3.4 Issues with Assessing a Naturally Ventilated BuildingOverall naturally ventilated buildings are more difficult to assess than their mechanicallyventilated counterparts, as they have more temperature variation, varying ventilation rates thatare dependent on environmental conditions and window geometry and less controlled airflowpatterns. This requires additional attention when determining air exchange rates, and in this case,the development and construction of a device to fit completely over the window to obtain moreaccurate volume flow rate measurements.51