CAN CGSB-149 15 AMD 1-1999 Determination of the Overall Envelope Airtightness of Buildings by the Fan Pressurization Method Using the Building-s Air Handling Systems.pdf

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1、CANICGSB-149.15-96 AMENDMENT NO. 1 MODIFICATIF N 1 AprilIAvril 1999 CANADIAN GENERAL OFFICE DES NORMES STANDARD BOARD GNRALESDU CANADA DETERMINATION OF THE OVERALL DTERMINATIONDE LITANCHIT LIAIR ENVELOPE AIRTIGHTNESS OF BUILDINGS BY GLOBALE DES ENVELOPPES DE BTIMENTS PAR THE FAN PRESSURIZATION METHO

2、D USING LA MTHODE DE DPRESSURISATION PAR THE BUILDINGS AIR HANDLING SYSTEMS VENTILATEURAU MOYEN DES SYSTMES DE TRAITEMENT DAIR DES BTIMENTS Add the following new Appendix F: Ajouter la nouvelle annexe F qui suit: APPENDIX F APPROACHES FOR DETERMINING AIR LEAKAGE CHARACTERISTICS OF BUILDINGS TABLE OF

3、 CONTENTS BACKGROUND.F2 COMMENTARY F3 PREFACE .F3 SCOPE AND FIELD OF APPLICATION . F5 PRINCIPLE F7 REFERENCED PUBLICATIONS . F8 TERMINOLOGY F9 APPARATUS F9 CALIBRATION OF TEST APPARATUS .F9 TESTING . F9 CALCULATIONS. FI4 TEST REPORT FI4 ATTACHEMENT A: DATA SHEETS FI5 BACKGROUND Air leakage into and

4、out of a building occurs mainly through unintentional openings, such as cracks formed at the joints of various envelope components. The size of the envelope leakage area of a building is a key factor in determining the magnitude of the air infiltration and exfiltration rates across the building enve

5、lope due to stack effect and wind. The pressure differences and uncontrolled air leakage can cause several problems including the following: -unbalanced performance of air distribution systems; - condensation; -cold drafts and comfort problems; -interference with proper operation of entrance doors,

6、elevator doors and some types of smoke control systems; and -much larger heating loads and high energy consumption. Knowledge of the air leakage characteristics of a building envelope is required to prevent undesirable air movement, to ensure efficient performance of the air handling systems, and to

7、 reduce the energy consumption. Over the years, the building shell construction practices have changed significantly with regards to airtightness. The 1995 National Energy Code for Buildings stipulates the requirements for the minimum air leakage performance of the building envelopes. Recent demonst

8、rations of low energy commercial buildings, such as IDEAS Challenge by CMHC and the C-2000 Program by NRCan, are targeted to meet certain airtightness criteria. To address the various building airtightness requirements in new construction and the retrofits of existing buildings, a CGSB standards com

9、mittee was formed to provide standardized test procedures and standard methods for measuring air leakage characteristics. The CGSB standard CANICGSB-149.15-96 deals with a test procedure to determine the overall building envelope airtightness of buildings by fan pressurization or depressurization us

10、ing the buildings air handling systems. A need for an accompanying commentary for the standard was identified by the CGSB committee due to the wide variety of buildings and building air handling systems, and the complexity of test procedures. The Commentary section provides explanations of various c

11、lauses of the standard as well as guidance on practical approaches that will be required to undertake testing of buildings. COMMENTARY The CGSB standard CANICGSB-149.15-96 can be used to determine the airtightness of the entire building envelope or the enclosed test section of the building. The buil

12、dings ventilation system is used for pressurizing or depressurizing the test volume. The airtightness tests can be conducted for the whole building volume or any part of the building. The test results can provide the airtightness values for building envelope. It should be noted that this method does

13、 not directly determine the quantity of actual air leakage, which occurs through the building envelope under the natural influences of wind and buoyancy pressures, or as a result of pressures produced by the operation of air handling systems. The airtightness characteristics of the building envelope

14、 obtained from the test can be used in the precise modeling of airflow through the building envelope. The following sections provide the explanations of various clauses in the standard. PREFACE This Commentary pertains to the CGSB standard CANICGSB-149.15-96, “Determination of the Overall Envelope A

15、irtightness of Buildings by the Fan Pressurization Method Using the Buildings Air Handling Systems.“ The main objectives of the Commentary are to provide details on the technical requirements and to offer explanation of various clauses and also to show feasible approaches for determining the air lea

16、kage characteristics of buildings. This standard can be applied to those buildings that have sufficient built-in air handling capacity. The air handling system can be either in supply or exhaust modes. The airtightness of the building envelope is determined using the buildings installed air handling

17、 system. The air handling system is configured to create a pressure difference across the enclosed building envelope. The enclosed test volume can either be pressurized using the supply air systems or depressurized using the exhaust air systems. Readings are taken of the airflow rate required to gen

18、erate the necessary pressure difference across the envelope. A minimum of four sets of pressure and airflow readings is required to develop a correlation representing the airtightness of the building envelope. This procedure helps in determining the average air leakage rate of the enclosed envelope

19、at a specified pressure difference. The buildings air handling system should be capable of pressurizing the interior zone(s) up to 60 Pa. However, for buildings incapable of obtaining 60 Pa, a minimum of 30 Pa is needed in order to obtain reasonable results. The capacity of the air handling system,

20、either in supply or exhaust modes, should be at least in the range of 1.0 to 2.5 LIS per square meter of the building envelope considered in the test volume. For example, for a building with an envelope area of 12 000 m2, the capacity of the air handling system serving the test volume capacity shoul

21、d be about 30 000 LIS. One of the principal requirements is to ensure that the test volume is sufficiently isolated from other non-test areas of the building and with a minimal amount of operational interference. It is our experience that in most commercial buildings, especially ofice and industrial

22、 buildings, the air handling capacity is suficienly larger than what would be required for conducting the airtightness tests. The required capacity of air handling systern can further be reduced to 0.7 to 1.5 Lls per square meter of envelope area for buildings that are built after 1990 due to recent

23、 air barrier requirernents. 1 Extract damper Outdoor air damper (closed) (open) *Return fan (off) I Return damper (closed) Floor return Floor supply Dampers Dampers (closed) (open) Note: State of fans and dampers during pressurization test conditions are shown in brackets. FIGURE FI Schematic of Air

24、 Handling System Used for Pressurization Using Buildings Interna1 Fans This Cornrnentary provides the brief background on the scope and objectives of airtightness testing of relatively large buildings. The procedure described in the standard is expected to give results within f10%. The Commentary se

25、ction provides explanations of various clauses of the standard as well as guidance on practical approaches that will be required to undertake testing of buildings. Its intent is to provide a guide to practitioners for undertaking airtightness tests. In the event of contradiction of comments with the

26、 clauses presented in the standard, the interpretation of clauses presented in the standard must be considered binding in meeting the requirements of the standard. Some of the test set-up and preparations may violate building and fire code requirements. Therefore, suitable approvals should be obtain

27、ed from qualified authorities. It is recommended that the test team closely monitor fire, health and safety measures during the test period. SCOPE AND FIELD OF APPLICATION The technique described in the standard can be used in buildings where the movement of a large volume of air is needed to create

28、 the required pressure differentials. The main criteria are that the air handling system must be able to produce pressure differentials across the building envelope in the required range (ideally O to 60 Pa), and that it must be possible to accurately measure the total air flow rate through the syst

29、em when it is in operation. This standard can be applied to al1 types of buildings and structures where the buildings own air handling system can provide the required flow rates to create the necessary pressure drop across the building enelope. The air handling system can be operated either in suppl

30、y or exhaust modes during the test. In some special cases, the standard can be applied where the capacity of the existing air handling system can be augmented using the additional equipment to obtain the necessary air-flow rates to generate the required pressure differentials across the building env

31、elope. The procedure can be applied to office buildings (low-rise to ta11 buildings), large warehouses, industrial facilities and, in some cases, multi-residential buildings. There may be different requirements for the preparation of the field test for different types of buildings. For example, for

32、ta11 buildings, the effects of the indoor and outdoor temperature difference and the wind speed would be more critical during the test than on the low-rise buildings. There are a lot of variations in the building layouts, construction practices and built-in air handling systems. The procedure descri

33、bed in the standard can be adapted to a variety of buildings and air handling configurations. Prescreening The prescreening criteria to determine whether this standard can be used for determining the airtightness values of the building envelope are given in Table 1. Failure to meet any of the basic

34、application requirements would disqualify the application of the test procedure. Qualifications Qualified persons should undertake the airtightness testing. The following should be considered: a. The building services site staff (maintenance and operation) must be consulted by the test team at al1 s

35、tages of the set-up procedure, thus making full use of detailed information about the operation of the air handling system. It is recommended that the test team include building operation or maintenance staff who are familiar with the existing system and controls. b. A qualified HVAC technician must

36、 be available at the time of the test to shut down combustion equipment as well as to reset or reprogram the damper controls. c. Basic understanding of the air handling equipment, controls and interaction of various air handling systems in the building is required for planning the test. d. The team

37、must obtain necessary approvals for accessibility to major equipment, air distribution components, dampers, controls, etc., prior to the test. e. In most cases, prior preparation is required for airflow and pressure measuring devices, custom- built control devices and sealing planes. f. Because of t

38、he disruption this technique causes to the normal operation of the air-handling system, the test procedure and measuring devices should be used with care and preferably at a time when any disturbance to the building occupants will be kept to a minimum. 2 For a building incapable of obtaining 60 Pa,

39、a minimum of 30 Pa is needed in order to obtain reasonable results. 3 The capacity of the air handling system either in supply or exhaust modes should be at least in the range of 1 .O to 2.5 LIS per square meter of the building envelope considered in the test volume. The required capacity of air han

40、dling system can further be reduced to 0.7 to 1.5 LIS per square meter of envelope area for buildings that are built after 1990 due to recent air barrier requirernents. g. During the building testing, some of the test set-up preparations may violate building and fire code requirements. Therefore, su

41、itable approvals should be obtained from qualified authorities prior to conducting tests. It is recommended that the test team closely monitor fire, health and safety measures during the test period. In the event of an emergency, testing must be abandoned and the building systems restored to pretest

42、 conditions. TABLE 1 Prescreening Criteria to Determine the Applicability of the Test Procedure During the planning stage, one should answer the following questions for determining the applicability of the test procedure as described in the standard. Failure to satisfy any of the following criteria

43、would disqualify the application of this standard. 1. Does the building have its own mechanical air handling system? -Yes -No 1s the capacity of the air handling system either in supply or exhaust modes at least 2. in the range of 1.0 to 2.5 LIS per square meter of the building envelope considered -

44、Yes -No in the test volume? Can the ventilation system airflow rate be varied sufficiently to develop a range of 3. pressure differences across the building envelope? -Yes -No 4. Can the airflow rate be accurately measured? -Yes -No 5. Can the test volume be physically isolated from other non-test z

45、ones? -Yes -No Can the air handling system for the test volume be sufficiently isolated from other 6 systems connected to non-test zones? -Yes -No 7. 1s the test area adequately interconnected, i.e. stairs, elevator shaft, etc? -Yes -No Are the weather conditions suitable for testing, for example, i

46、s wind speed less than 20 kmlh? -Yes -No F1.4 Limitations of the Standard he procedure described in the standard can be applied to al1 those buildings or facilities where the air iandling system can be used to pressurize or depressurize the test volume. Due to the wide variety of uildings and comple

47、xity of air handling systems, in some cases, this standard may not be applicable. The following lists some of the physical limitations: 1. The inability of the air handling system to provide the necessary airflow rates required to achieve an adequate range of pressure difference across the building

48、envelope enclosing the test area. ). If the test volume has large physical interconnections to other non-test zones or other buildings that cannot be sufficiently isolated, the test procedure in this case would be ineffectual. Due to a large number of penetrations through floors, it is sometimes dif

49、ficult to physically isolate the test section. In this case, necessary test requirements will not be met. 1. Generally, in large buildings, there are many main air handling systems either supplying or returning (exhausting) air from the test zone. During the test, the air handling stream(s) used for the test volume should be sufficiently independent from other main air systems. In the case of interconnected systems, one should be able to measure airflow rates at different segments of various systems to determine the net airflow rate for the test volume. Failure t