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

As natural ventilation is prevalent in the United Kingdom, standards have been developed forboth mechanically and naturally ventilated buildings. Table 3 provides an example of typicalstandards. The Energy Consumption Guide 019 (ECG019) classifies both mechanically andnaturally ventilated buildings into two categories; standard and prestige for mechanicallyventilated buildings, and naturally ventilated cellular and naturally ventilated open-plan.Benchmarks like those in Table 4 also provide data as to standard practice (Std.), which does notemploy energy saving equipment or technologies, and good practice (GP), which does.Table 4. Energy Consumption Guide 019 Building Characteristic Data for UK 2Building Type Configuration Floor AreaMechanically Ventilated (MV) 2,000-20,000m 2Naturally Ventilated (NV) Cellular 100-3,000m 2Open Plan 500-4,000m 2Table 5. ECG 019 Benchmark Data for UK by Building Type 2Energy End Use MV Std. MV GP NV Std. NV GPLighting, W/m 2 20 12 15-18 12Office Equip, W/m 2 16-18 14-15 12-14 10-12Lighting, kWh/m 2 54-60 27-29 23-38 14-22Office Equip., kWh/m 2 31-32 23 18-27 12-20Heating, kWh/m 2 178-201 97-107 151 79Table 5 shows the energy use, in watts per square meter and kilowatt-hours per square meter forthe two building ventilation types and the range (Std. and GP) prescribed for UK office buildingsby the ECG019. Energy use in kilowatt-hour per floor area is dependent on the number of hoursthat the energy using system operates. For the ECG 019, this varies by both building andventilation type due to the configuration of the building and the incorporation of energyconserving technologies and practices. ECG019 purports that naturally ventilated buildings havea lower lighting, office equipment, and occupant density than mechanically ventilated buildings.This is in part due to limits with the amount of heating load that the natural ventilation schemecan successfully handle and the attention to detail in opportunities to reduce any additional heatloads within the occupied space to control the magnitude of the heat load. This leads to theslightly lower numbers when comparing the standard MV and NV energy end use numbers. Theheating energy usage is slightly lower for the NV than MV buildings due to the designcharacteristics, such as thermal mass, that are incorporated into the design and the lower fresh airrequirement with the reduced occupant load.2.4.7 Characteristics Unique to Naturally Ventilated BuildingsThere are several common configurations and methods for enhancing natural ventilation inbuildings. The two main drivers for natural ventilation are buoyancy-driven and wind-drivenflows. These are often both found working together in naturally ventilated buildings. Some ofthe concern with incorporating natural ventilation as the sole means for cooling the building iswith still days, when only buoyancy driven ventilation is present. In this case, airflow through2Energy Consumption Guide 019 200340