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

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of cooling required by 30 percent or more, and decrease internal room temperatures by 5°C(Daniels 2003) when compared to lower mass buildings. During summer months thermal masscan be exposed to the lower, nighttime temperatures, in effect pre-cooling the interior spaceduring un-occupied hours. This effect is often created by drawing in cooler night air, andthereby pre-cooling the thermal mass. The pre-cooled thermal mass is then able to temper theinterior temperature during occupied hours, counteracting the build up of heat due to interiorloads. The cooling period takes advantage of the natural diurnal swings of the exteriorenvironment, capturing the cooling energy provided by the lower outside temperatures. In thisway, the internal temperature of the building is moderated; not getting as cold as the environmentduring the nighttime, but also not reaching the high temperatures occurring during midday toearly afternoon. Thermal mass is known for causing ‗peak shifting‘, when the peak internaltemperature occurs well after the peak outside temperature. Sometimes the peak internaltemperature occurs at the end of the workday when there are fewer occupants. In the heatingseason, the thermal mass retains heat generated by the internal loads during the daytime hours,and releases the heat during nighttime hours so that the building does not get as cold or require asmuch additional heating during un-occupied hours.2.3.4 Integration of Design DetailsThe above described techniques are important to the enhancement of natural ventilationindividually; however they can increase the performance of a naturally ventilated building muchmore when two or more are integrated in the building design. It is not uncommon to havewindow type and location selected based on the layout of the building floor plan due to the typeof ventilation, single-sided or cross ventilation, that is planned. Through careful design, many ofthese building characteristics can be incorporated into the overall design of a naturally ventilatedbuilding to ensure proper airflow, occupant comfort, and overall building performance.2.3.5 Prototype Building CharacteristicsThe prototype building, described in detail in Chapter 3, included several of the above naturalventilation enhancing techniques. The building was located in a relatively open office park, withbuildings of similar height. Attention to details such as the selection of building material,increasing daylight within the office space, decreasing solar gain and glare, and office layoutresulted in a naturally ventilated commercial office building that functions well without the needfor mechanical cooling.The material selection for the façade differed from the north to the south side, in part due toarchitectural aesthetics, but also due to the orientation of the building. On the southern façade,light colored materials help reflect some of the solar isolation, whereas on the northern façade,bricks were used as the facing material. Other design details that were incorporated into theprototype building include solar shading to reduce direct solar glare, and light shelves to allowthe natural daylight to penetrate deeper into the office space. Through the use of the lightshelves, the electric energy consumed by the general lighting can be reduced because the fixturesare outfitted with photo-sensors and are dimmable down to 10 percent. The building usesthermal mass to help temper the interior temperature by leaving small, upper windows open atnight during the summer months to pre-cool ceiling soffits. The cross section of the ground floorof the prototype building with these design characteristics is shown in Figure 10.34
Figure 10. Prototype Building Design Characteristics2.4 Building Performance EvaluationA prototype building was selected to evaluate a scale modeling technique for naturally ventilatedbuildings. The building is a commercial office building, built and owned by the company thatoccupies the building. The company is an organization dedicated to providing housing andassistance to individuals and families in need, and thus desired a building that had relatively lowconstruction and operational costs. The building is an example of the type of commercial officebuilding currently being constructed that uses an open floor plan to allow for the greatest amountof flexibility, and incorporates much glazing into the building façade to take advantage ofavailable natural daylight. The natural daylight throughout the building, particularly in thoseareas towards the center of the floor plan, provides an aesthetic of an open building, which isenhanced by the glass atrium included in the design. This feature is common to manycommercial office buildings, both mechanically ventilated and naturally ventilated ones.Several aspects of a building contribute to the overall building operation, such as thermalperformance, ventilation performance, and energy performance. Each of these areas has animpact on specific systems of a building, yet they are interrelated, contributing not only to theoverall performance of a building but also to the health and comfort of its occupants. Monitoringof buildings is not new, but applying the knowledge and assessing naturally ventilated buildingscan pose some difficulties. A multi-pronged approach was taken to fully evaluate the naturallyventilated office building, including long-term and short-term monitoring, and surveyingoccupant behavior. This method provided adequate data on the overall building performanceunder a variety of conditions. Some aspects of these data were then used to determine how thebuilding functioned relative to other buildings as well as compliance with building codes, as isthe case with ventilation. Natural ventilation in particular has unique characteristics that must be35
Page 2 and 3: Thesis Committee:Leon R. Glicksman,
Page 4 and 5: Table of ContentsTable of Contents
Page 6 and 7: 7.1.3 Full Model Case .............
Page 8 and 9: Figure 41. Wind Direction Data for
Page 10 and 11: List of TablesTable 1. Energy End U
Page 12 and 13: Table 64. Comparison of Dimensionle
Page 15 and 16: Chapter 1.0IntroductionEnergy consu
Page 17 and 18: insulated building envelopes with t
Page 19 and 20: energy usage and efficient design.
Page 21 and 22: Figure 3. European Patent Office Bu
Page 23: selecting boundary conditions) to e
Page 26 and 27: 2.2.1 Buoyancy-Driven VentilationVe
Page 28 and 29: Figure 7. Neutral Pressure Level fo
Page 30 and 31: Combined wind-buoyancy flow is more
Page 32 and 33: design. The depth of natural ventil
Page 36 and 37: considered when determining how the
Page 38 and 39: environmental conditions are examin
Page 40 and 41: As natural ventilation is prevalent
Page 43 and 44: Chapter 3.0Evaluation of Prototype
Page 45 and 46: Figure 12. Interior Atrium ViewFigu
Page 47 and 48: Table 8. Prototype Building Window
Page 49 and 50: Figure 15. HOBO® H8 Series Tempera
Page 51 and 52: Finally, airflow visualization was
Page 53 and 54: only is the airflow almost never at
Page 55 and 56: Table 10. Window Bag Device Measure
Page 57 and 58: Mon 7-21Tue 7-22Wed 7-23Thu 7-24Fri
Page 59 and 60: 12:00 AM1:00 AM2:00 AM3:00 AM4:00 A
Page 61 and 62: 27-Jul27-Jul28-Jul28-Jul29-Jul30-Ju
Page 63 and 64: A range of air exchange rates was f
Page 65 and 66: the windows on the second floor, or
Page 67 and 68: Total Electric (kWh/m2)Total Gas (k
Page 69 and 70: movement, Houghton Hall has much le
Page 71 and 72: Chapter 4.0Modeling and Visualizati
Page 73 and 74: for future design of similar type b
Page 75 and 76: lower and upper openings and natura
Page 77 and 78: the acceptable diffusion rate, or
Page 79 and 80: applications involving full-scale b
Page 81 and 82: digital camera with both manually o
Page 83 and 84: Chapter 5.0Dimensional Analysis and
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u oHgHT2uocu Hpo1Re Ar1Re Pr(5.7)(5
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X HM X HP(5.16)5.3.2 Kinematic Sim
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Radiation was found to have an impa
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height is used for the full-scale b
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6.3 Model Descriptions6.3.1 Physica
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Figure 30. Floor Plan of the Protot
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Figure 31. North Facade of Model wi
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Monitoring data collected from the
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By default, there was no accounting
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40-location card inserted into the
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6.5 ExperimentsTo evaluate the mode
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modified to determine the impact of
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Figure 39. Two Heated Zone ModelWit
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minute interval, the model was assu
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Figure 42. Cross-Section of Wind-Ge
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Table 25. Wind-Assisted Ventilation
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Figure 44. Heaters and Zones for a)
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Height from Floor (m)Height from Fl
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Where V is the outlet velocity, A o
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Table 32. Conduction Heat Loss for
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a) Air Modelb) Water ModelFigure 50
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Height from Floor (m)The temperatur
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Height from Floor (m)In the atrium
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First NorthUpper Window 0.17 m/s -0
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Height from Floor (m)the column at
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Height from Floor (m)Height from Fl
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Height from Floor (m)3.53.02.52.01.
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was less than 12 percent. These val
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Table 39. Variation of Outlet Wind
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temperature of the air was the same
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3.532.521.55m/s4m/s3m/s2m/s1m/s1.5m
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3.532.521.55m/s4m/s3m/s2m/s1m/s1.5m
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The average and exhaust internal bu
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Table 43. Calculated Wind and Buoya
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In the last two lines, for both the
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Figure 80. CFD Simulation of the Te
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uoyancy case the air from the groun
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160
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windows of naturally ventilated bui
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difficult to select the boundary co
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simulations are able to do would al
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Bordass, W.T., A.K.R. Bromley and A
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Linddament, M. 1996. Why CO2? Air I
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172
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MODEL: K20-8SERIAL: 10047RECORDER_I
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2 Boiler-3 50.00 C1 N1 1.0 ON ON OF
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|PW|DESCRIP |KW |KWH|KVA|KVH|------
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2:5 ;day_ofYr17:P30 ;EOT = 0.000075
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2:3136:P30 ;DUM2 = -0.040891:-4.089
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;7:21 ;input location;8:0 ;mulptipl
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;79:P22 ;EXC w/DELAY (only for dela
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1:45 ;port5 (homeSense)2:31 ;exit l
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13:P95 ;ENDIF14:P95 ;ENDIF15:P3 ;pu
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2:20 ;RH30:P70 ;sample1:12:20 ;RH31
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194
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Five Windows Open: Upper versus Low
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One Window Open: Upper versus Lower
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25 cm / 3 m 24.33 26.62 22.68 22.93
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25 cm / 3 m 24.07 25.26 22.65 22.78
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Two Stacks Open Temperature Stratif
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Stacks Closed Temperature Stratific
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2.3 24.31 24.65 24.781.4 23.35 23.6
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0.6 20.56 20.67 20.94 21.22 21.41 2
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