ASHRAE HVAC APPLICATIONS IP CH 3-2015 COMMERCIAL AND PUBLIC BUILDINGS.pdf

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1、3.1CHAPTER 3COMMERCIAL AND PUBLIC BUILDINGSOffice Buildings. 3.1Transportation Centers . 3.6Warehouses and Distribution Centers 3.8Sustainability and Energy Efficiency 3.9Commissioning and Retrocommissioning. 3.12Seismic and Wind Restraint Considerations. 3.12HIS chapter contains technical, environm

2、ental, and design con-Tsiderations to assist the design engineer in the proper applica-tion of HVAC systems and equipment for commercial and publicbuildings.1. OFFICE BUILDINGSGeneral Design ConsiderationsDespite cyclical market fluctuations, office buildings are consid-ered the most complex and com

3、petitive segments of real estatedevelopment. Survey data of 824,000 office buildings (EIA 2003)demonstrate the distribution of the U.S. office buildings by the num-bers and the area, as shown in Table 1.According to Gause (1998), an office building can be divided intothe following categories:Class.

4、The most basic feature, class represents the buildingsquality by taking into account variables such as age, location, build-ing materials, building systems, amenities, lease rates, etc. Officebuildings are of three classes: A, B, and C. Class A is generally themost desirable building, located in the

5、 most desirable locations, andoffering first-rate design, building systems, and amenities. Class Bbuildings are located in good locations, have little chance of func-tional obsolescence, and have reasonable management. Class Cbuildings are typically older, have not been modernized, are oftenfunction

6、ally obsolete, and may contain asbestos. These low stan-dards make Class C buildings potential candidates for demolition orconversion to another use.Size and Flexibility. Office buildings are typically grouped intothree categories: high rise (16 stories and above), mid rise (four to15 stories), and

7、low rise (one to three stories).Location. An office building is typically in one of three loca-tions: downtown (usually high rises), suburban (low- to mid-risebuildings), or business/industrial park (typically one- to three-story buildings).Floorplate (Floor Space Area). Size typically ranges from18

8、,000 to 30,000 ft2and averages from 20,000 to 25,000 ft2.Use and Ownership. Office buildings can be single tenant ormultitenant. A single-tenant building can be owned by the tenant orleased from a landlord. From an HVAC HVAC systems such as single-zone constant-volume,water-source heat pump, and pac

9、kaged terminal air conditioners(PTACs) might be inapplicable to this class, whereas properlydesigned variable-air-volume (VAV) systems can meet these require-ments.Design CriteriaA typical HVAC design criteria covers parameters required forthermal comfort, indoor air quality (IAQ), and sound. Therma

10、l com-fort parameters (temperature and humidity) are discussed inASHRAE Standard 55-2010 and Chapter 9 of the 2013 ASHRAEHandbookFundamentals. Ventilation and IAQ are covered byASHRAE Standard 62.1-2010, the users manual for that standard(ASHRAE 2010), and Chapter 16 of the 2013 ASHRAE Hand-bookFund

11、amentals. Sound and vibration are discussed in Chapter48 of this volume and Chapter 8 of the 2013 ASHRAE HandbookFundamentals.Thermal comfort is affected by air temperature, humidity, airvelocity, and mean radiant temperature (MRT), as well as nonenvi-ronmental factors such as clothing, gender, age,

12、 and physical activ-ity. These variables and how they correlate to thermal comfort canbe evaluated by the Thermal Comfort Tool CD (ASHRAE 1997) inconjunction with ASHRAE Standard 55. General guidelines fortemperature and humidity applicable for areas in office buildingsare shown in Table 2.All offic

13、e, administration, and support areas need outdoor air forventilation. Outdoor air is introduced to occupied areas and thenexhausted by fans or exhaust openings, removing indoor air pollut-ants generated by occupants and any other building-related sources.ASHRAE Standard 62.1 is used as the basis for

14、 many buildingcodes. To define the ventilation and exhaust design criteria, consultlocal applicable ventilation and exhaust standards. Table 3 providesrecommendations for ventilation design based on the ventilationrate procedure method and filtration criteria for office buildings.Acceptable noise le

15、vels in office buildings are important foroffice personnel; see Table 4 and Chapter 48.Load CharacteristicsOffice buildings usually include both peripheral and interiorzone spaces. The peripheral zone extends 10 to 12 ft inward fromthe outer wall toward the interior of the building, and frequently h

16、asTable 2 Typical Recommended Indoor Temperature and Humidity in Office BuildingsAreaIndoor Design ConditionsTemperature, F/Relative Humidity, %CommentsWinter SummerOffices, conference rooms, common areas70.0 to 74.0 74.0 to 78.020 to 30% 50 to 60%Cafeteria 70.0 to 73.5 78.520 to 30% 50%Kitchen 70.0

17、 to 73.5 84.0 to 88.0 No humidity controlToilets 72.0 Usually not conditionedStorage 64.0 No humidity controlMechanical rooms 61.0 Usually not conditionedTable 3 Typical Recommended Design Criteria for Ventilation and Filtration for Office BuildingsCategoryVentilation and Exhausta,bMinimum Filtratio

18、n Efficiency, MERVcCombined Outdoor Air (Default Value) cfm per PersonOccupant Density,fper1000 ft2Outdoor Aircfm/ft2cfm per UnitOffice areas 17 5 6 to 8Reception areas 7 30 6 to 8Main entry lobbies11 10 6 to 8Telephone/data entry660 6 to 8Cafeteria 9 100 6 to 8Kitchend,e0.7 (exhaust)NAToilets 70 (e

19、xhaust)NAStorageg0.12 1 to 4Notes:aBased on ASHRAE Standard 62.1-2010, Tables 6-1 and 6-4. For systems servingmultiple zones, apply multiple-zone calculations procedure. If DCV is considered, seethe section on Demand Control Ventilation (DCV).bThis table should not be used as the only source for des

20、ign criteria. Governing localcodes, design guidelines, ANSI/ASHRAE Standard 62.1-2010 and users manual,(ASHRAE 2010) must be consulted.cMERV = minimum efficiency reporting values, based on ASHRAE Standard 52.2-2007.dSee Chapter 33 for additional information on kitchen ventilation. For kitchenette us

21、e0.3 cfm/ft2.eConsult local codes for kitchen exhaust requirements.fUse default occupancy density when actual occupant density is not known.gThis recommendation for storage might not be sufficient when the materials storedhave harmful emissions.Table 4 Typical Recommended Design Guidelines for HVAC-

22、Related Background Sound for Areas in Office BuildingsCategorySound Criteriaa,bCommentsRC (N);QAI 5 dBExecutive and private office25 to 35Conference rooms 25 to 35Teleconference rooms 25Open-plan office space4035 With sound maskingCorridors and lobbies 40 to 45Cafeteria 35 to 45 Based on service/sup

23、port for hotelsKitchen 35 to 45 Based on service/support for hotelsStorage 35 to 45 Based on service/support for hotelsMechanical rooms 35 to 45 Based on service/support for hotelsNotes:aBased on Table 1 in Chapter 48.bRC (room criterion), QAI (quality assessment index) from Chapter 8 of the 2013ASH

24、RAE HandbookFundamentals.Commercial and Public Buildings 3.3a large window area. These zones may be extensively subdivided.Peripheral zones have variable loads because of changing sun posi-tion and weather. These zones typically require heating in winter.During intermediate seasons, one side of the

25、building may requirecooling, while another side requires heating. However, the interiorzone spaces usually require a fairly uniform cooling rate through-out the year because their thermal loads are derived almost entirelyfrom lights, office equipment, and people. Interior space condition-ing is ofte

26、n by systems that have VAV control for low- or no-loadconditions.Most office buildings are occupied from approximately 8:00 AMto 6:00 PM; many are occupied by some personnel from as early as5:30 AM to as late as 7:00 PM. Some tenants operations may requirenight work schedules, usually not beyond 10:

27、00 PM. Office build-ings may contain printing facilities, information and computingcenters, or broadcasting studios, which could operate 24 h per day.Therefore, for economical air-conditioning design, the intendeduses of an office building must be well established before designdevelopment.Occupancy

28、varies considerably. In accounting or other sectionswhere clerical work is done, the maximum density is approximatelyone person per 75 ft2of floor area. Where there are private offices,the density may be as little as one person per 200 ft2. The most seri-ous cases, however, are the occasional waitin

29、g rooms, conferencerooms, or directors rooms, where occupancy may be as high as oneperson per 20 ft2.The lighting load in an office building can be a significant partof the total heat load. Lighting and normal equipment electricalloads average from 1 to 5 W/ft2but may be considerably higher,dependin

30、g on the type of lighting and amount of equipment. Build-ings with computer systems and other electronic equipment canhave electrical loads as high as 5 to 10 W/ft2. The amount, size, andtype of computer equipment anticipated for the life of the buildingshould be accurately appraised to size the air

31、-handling equipmentproperly and provide for future installation of air-conditioningapparatus.Total lighting heat output from recessed fixtures can be withdrawnby exhaust or return air and thus kept out of space-conditioningsupply air requirements. By connecting a duct to each fixture, themost balanc

32、ed air system can be provided. However, this methodis expensive, so the suspended ceiling is often used as a return airplenum with air drawn from the space to above the suspendedceiling.Miscellaneous allowances (for fan heat, duct heat pickup, ductleakage, and safety factors) should not exceed 12% o

33、f the total load.Building shape and orientation are often determined by the build-ing site, but some variations in these factors can increase refrigera-tion load. Shape and orientation should therefore be carefullyanalyzed in the early design stages.Design ConceptsThe variety of functions and range

34、of design criteria applicable tooffice buildings have allowed the use of almost every available air-conditioning system. Multistory structures are discussed here, butthe principles and criteria are similar for all sizes and shapes ofoffice buildings.Attention to detail is extremely important, especi

35、ally in modularbuildings. Each piece of equipment, duct and pipe connections, andthe like may be duplicated hundreds of times. Thus, seeminglyminor design variations may substantially affect construction andoperating costs. In initial design, each component must be analyzednot only as an entity, but

36、 also as part of an integrated system. Thissystems design approach is essential for achieving optimum results.As discussed under General Design Considerations, there areseveral classes of office buildings, determined by the type of financ-ing required and the tenants who will occupy the building. De

37、signevaluation may vary considerably based on specific tenant require-ments; it is not enough to consider typical floor patterns only. Manylarger office buildings include stores, restaurants, recreational facil-ities, data centers, telecommunication centers, radio and televisionstudios, and observat

38、ion decks.Built-in system flexibility is essential for office building design.Business office procedures are constantly being revised, and basicbuilding services should be able to meet changing tenant needs.The type of occupancy may have an important bearing on air dis-tribution system selection. Fo

39、r buildings with one owner or lessee,operations may be defined clearly enough that a system can bedesigned without the degree of flexibility needed for a less well-defined operation. However, owner-occupied buildings may requireconsiderable design flexibility because the owner will pay for allaltera

40、tions. The speculative builder can generally charge alterationsto tenants. When different tenants occupy different floors, or evenparts of the same floor, the degree of design and operation complex-ity increases to ensure proper environmental comfort conditions toany tenant, group of tenants, or all

41、 tenants at once. This problem ismore acute if tenants have seasonal and variable overtime schedules.Certain areas may have hours of occupancy or design criteria thatdiffer substantially from those of the office administration areas;such areas should have their own air distribution systems and, inso

42、me cases, their own heating and/or refrigeration equipment.Main entrances and lobbies are sometimes served by a separateand self contained system because they buffer the outdoor atmo-sphere and the building interior. Some engineers prefer to have alobby summer temperature 4 to 6F above office temper

43、ature toreduce operating cost and temperature shock to people entering orleaving the building. In cases where lobbies or main entrances havelonger (or constant) operation, a dedicated/self-contained HVACsystem is recommended to allow turning off other building systems.The unique temperature and humi

44、dity requirements of serverrooms or computer equipment/data processing installations, and thefact that they often run 24 h per day for extended periods, generallywarrant separate refrigeration and air distribution systems. Separateback-up systems may be required for data processing areas in casethe

45、main building HVAC system fails. Chapter 19 has further infor-mation.The degree of air filtration required should be determined. Ser-vice cost and effect of air resistance on energy costs should be ana-lyzed for various types of filters. Initial filter cost and air pollutioncharacteristics also need

46、 to be considered. Activated charcoal filtersfor odor control and reduction of outdoor air requirements areanother option to consider.Providing office buildings with continuous 100% outdoor air (OA)is seldom justified, so most office buildings are designed to mini-mize outdoor air use, except during

47、 economizer operation. How-ever, attention to indoor air quality may dictate higher levels ofventilation air. In addition, the minimum volume of outdoor airshould be maintained in variable-volume air-handling systems.Dry-bulb- or enthalpy-controlled economizer cycles should be con-sidered for reduci

48、ng energy costs. Consult ASHRAE Standard 90.1-2010 for the proper air economizer system (dry-bulb or enthalpy).When an economizer cycle is used, systems should be zoned so thatenergy is not wasted by heating outdoor air. This is often accom-plished by a separate air distribution system for the inter

49、ior and eachmajor exterior zone. A dedicated outdoor air system (DOAS) can beconsidered where the zones are served by in-room terminal systems(fan coils, induction unit systems, etc.) or decentralized systemse.g., minisplit HVAC, water-source heat pump (WSHP). Becausethe outdoor air supply is relatively low in office buildings, air-to-airheat recovery is not cost effective; instead, a DOAS with enhancedcooling and dehumidification systems can be used.These systems typically use hot-gas reheat or other means of freereheat (e.g., heat pipes, plate-frame heat exchangers). In h