fan preSSure teStinG

for LarGe, coMpLex buiLdinGS

terry brennan

camrOden assOciates, inc. 7240 East Carter Road, Westmoreland, NY 13490

Phone: 315-336-7955 • Fax: 315-336-6180 • E-mail: terry@camroden.com

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abStraCt

This paper will present the important lessons learned based on over 30 years of testing the airtightness of buildings. Common problems encountered while setting up and conduct­ing tests and their solutions will be presented. Details and locations that are difficult to air seal and those that are easy to air seal will be presented. Airtightness test targets and methods needed to achieve them will be covered. Buildings tested include commercial and institutional buildings, laboratories, hospitals, museums, pools, schools, warehouses, and industrial applications. They range in size from banana-ripening rooms to 13-story towers to 800,000-sq.-ft. warehouses. The results of the ASHRAE 1478 (Measuring Airtightness of Mid- and High-Rise Nonresidential Buildings) research project are included.

SPeaKer

terry brennan – camrOden assOciates, inc.

TERRy BRENNAN is a building scientist and educator and has studied buildings since the 1970s. He has provided research, investigation of building-related problems, training, curriculum development, and program support for the EPA, building owners and manag­ers, architects, engineers, and several state health departments. He is the technical lead for the ASHRAE 1478, Measuring Airtightness of Mid- and High-Rise Nonresidential Buildings research project. Brennan chairs the Air Barrier Association of America’s Whole Building Airtightness Testing Committee. This committee revised the Army Corps of Engineers’ whole-building test protocol in 2012 and is currently an ASTM Task Group (Wk35913) on New Standard Whole-Building Enclosure Airtightness Compliance. He is a member of ASTM E06 and ASHRAE 62.2, the committee on ventilation for low-rise residential build­ings. Brennan has served as a consultant to the National Academies of Science Committee on Dampness and Health in Buildings. He is the primary author of the forthcoming EPA Moisture Control Guide.

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fan preSSure teStinG

for LarGe, coMpLex buiLdinGS

INTRODUCTION Fan pressure tests are conducted to

test air barrier systems on whole buildings, apartments or suites of rooms, isolated special-use areas within buildings, and air-handling equipment (e.g., ducts, air handlers, and hot-air solar collectors). This paper focuses on testing entire building enclosures or apartments in multifamily buildings.

Fan pressurization tests may be con­ducted for one or more of the following reasons:

• To measure the airtightness of an enclosure to determine whether or not it meets an airtightness target

• To help find air leakage sites using infrared scanning, theatrical fog, or chemical smoke tracers

• As part of a quality assurance (QA) inspection and testing program for air barrier installation

• To assess the effectiveness of retrofit air-sealing efforts, either quantita­tively or qualitatively

• To measure air leakage rates or leakage areas for use in building energy-use calculations

• To test the ability of installed air barrier materials to resist specific pressure loads (typically assemblies are tested at pressure differences of 75 and 298 Pascals, and whole buildings are tested at 50 or 75 Pascals).

Whole-building fan pressurization tests have been conducted to measure the air­tightness of single-family residential build­ings in the U.S. and Canada since the 1970s. They have been extensively used in weatherization programs and as part of QA for high-performance homebuilding pro ­grams (e.g., EnergyStar, LEED® for Homes, and Passive House). Efforts to extend the tests to larger and more complex build­ings began in the 1980s. In the past ten years, North American manufacturers of test equipment have developed methods for networking test fans and electronic

micro-manometers so that test data can be collected and analyzed by computer soft­ware programs. This has made it practical to test larger buildings than ever before. The ASHRAE project, 1478-RP, Measuring Airtightness of Mid- and High-Rise Non-Residential Buildings, developed a test pro­tocol specifically for testing large build­ings and conducted tests on 16 buildings built since 2000 (Anis 2014). The build­ings ranged between four and 14 stories and between 54,000 and 362,000 sq. ft. in floor area. The tested buildings were located in climate zones 2 through 7 of the International Energy Conservation Code (IECC) Climate Zone Map. Tests were com­pleted between 2011 and 2012.

Over the last 30 years, manufacturers of building products have developed materials and systems that provide continuous air barrier systems in commercial and institu­tional buildings. During this time period, the use of air barrier systems in commer­cial and institutional buildings has become common practice.

By limiting airflow through the thermal enclosure, continuous air barriers perform two crucial functions in high-performance enclosures:

• Limiting heat transfer by accidental air leakage through the enclosure

• Limiting the transport of water vapor by accidental air leakage (e.g., preventing condensation by keep­ing warm, humid outdoor air away from air-conditioned, chilled interior surfaces; and keeping warm, humid indoor air from reaching exterior enclosure materials that are chilled by cold outdoor air)

In addition to blocking airflow, many air barrier materials act as capillary breaks and serve dual duty as both air barrier and rainwater control. Even in airtight assem­blies, condensation may occur if the vapor barrier is located in the wrong spot relative to more permeable insulating materials. Some air barrier materials accidentally or intentionally behave as nearly perfect water

vapor barriers, while others are more vapor-open. Condensation control must be evalu­ated for whole assemblies, because conden ­sation is a function of vapor migration and the surface temperature of materials.

Continuous air barriers are also required for buildings or rooms that are intended to shelter vulnerable occupants, materials, equipment, or processes from damaging environmental agents (e.g., bone marrow transplant wards; art, artifact, or musical instrument storage or display; computers and telecommunications equip­ment; lithium batteries; solid-state chip manufacturing). Air barriers are also used to prevent damaging, annoying, or valuable environmental agents from escaping from contained sources (e.g., biohazard level 3 or 4 containment, paint booths, fruit-ripening rooms).

Continuous air barriers are required by code in a dozen U.S. states and Canada. The ICC family of model codes requires continuous air barriers. One path to dem­onstrate compliance is for the results of a fan pressurization test to be equal to or less than an airtightness target. The Army Corps of Engineers (ACE), General Services Agency (GSA), EnergyStar multifamily high-rises, Passive House U.S. multifam­ily projects, and projects using the Unified Facilities Guide Specifications are required to have continuous air barriers and to pass a whole-building fan pressurization test. The ACE requirements for air barriers and whole-building testing have resulted in a large increase in the use of air barriers and fan pressure testing in commercial and institutional buildings.

TEST METHODS A fan pressure test is conducted on a

building enclosure by using fans to exhaust air from or blow air into a test enclosure. At its simplest, a qualitative test can be used to find air leaks in buildings. Air leaks can be found by simply feeling the breeze on the skin. Infrared scanning, theatrical fog, and smoke tracers can be used to make it easier or quicker to find air leaks in build-

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Figure 1 – A schematic illustration of a fan pressurization test.

ings. These methods are described in ASTM E1186, Standard Practices for Air Leakage Site Detection in Building Envelopes and Air Barrier Systems.

The fan pressure test becomes a quanti­tative test by measuring:

• The indoor/outdoor pressure induced across a building enclosure

• The exhaust or supply airflow required to induce the measured pressure difference as illustrated in Figure 1

Air is exhausted from the enclosure by a fan that is sealed into the wall. This low­ers the air pressure inside the box relative to the outside of the box, drawing air in through the air leaks in the enclosure (for simplicity, represented in Figure 1 as a sin­gle hole). The mass of air drawn in is equal to the mass of air exhausted through the fan. The airflow and the resulting change in indoor/outdoor pressure difference are measured. The tighter the box, the smaller the airflow required to induce a particular test pressure difference. Airflow and the resulting pressure difference are measures of enclosure airtightness.

Applying this simple concept to build­ings, we run into a few practical problems. Buildings are not simple, closed boxes with no interior airflow restrictions. They have open windows and doors. They are filled with partitions and floors that restrict airflow from one place to another. Fan-powered exhaust and outdoor air fans in an operating building induce pressure differ­ences between inside and outside the build­

ing. Indoor/outdoor pressure differences are affected by wind and stack effect.

To conduct a fan pressurization test, a building must be prepared so that it resem­bles the condition in Figure 1 as closely as possible. All the exterior windows and doors

must be closed (except those containing test fans). Interior doors must be opened to allow air to move freely throughout the building. Exhaust and outdoor air fans must be shut off and sealed, at least by closing dampers.

After a building is set up for a test, the effects of wind and stack effect pressures must be subtracted out. This is done by measuring a baseline pressure difference with the test fans turned off and sealed so that wind and stack effects are the only reason there would be an indoor/outdoor pressure difference. It is not the absolute indoor/outdoor pressure difference that is important, it is the amount the indoor/ outdoor pressure difference changes when a measured airflow is exhausted from or supplied to the enclosure. If the mass of air inside the box is an open, single zone, then the change in pressure difference is the same at all points on the enclosure. For the purposes of this paper, the pressure differ­ence induced between inside and outside by the operation of the test fan will be called the enclosure pressure.

There are two methods commonly used

Figure 2 – Repeated-reference pressure test. A baseline is collected, the test fans are turned on, the reference pressure is induced, and the airflow required is measured. Although not shown in this graph, the measured flow for the test was 15,200 cubic feet per minute (cfm) (corrected for temperature and altitude).

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to make a quantitative measurement of building air leakage. The simplest is the repeated single-reference pressure method. In this method, prepare the building as described above, measure a baseline pres­sure, turn on test fans until a reference enclosure pressure is reached, and measure the airflow required to induce the reference enclosure pressure. Repeat this procedure at least five times. Historically, reference test pressures of 50 Pascals and 75 Pascals have been used for this test. This method is described in ASTM E1827, Standard Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door, and Chapter 8 of the Residential Energy Services Network’s (RESNET’s) National Mortgage and Housing Home Energy Rating System (HERS) Standards. Figure 2 shows the results of a repeated single-reference pres­sure test.

This test illustrates the important prin­ciple that it is the change in the indoor/ outdoor pressure difference induced by the operation of the test fans that is important. The reference enclosure pressure for the test is 75 Pascals. The baseline averages around -8 Pascals. Baseline enclosure pres­sures measured at grade are frequently negative due to stack and wind effects. This is the case for low-rise and taller buildings during warm weather in air-conditioned buildings. Test fans provide supply airflow to raise the enclosure pressure 75 Pascals (from -8 to +67 Pascals). The reported result is 15,200 cfm at 75 Pascals. An airflow and an induced enclosure pressure are the fun­damental result. Repeating the test provides the data needed to calculate uncertainty in the measurements. (Note: Wind effects during this test seem to contribute plus or minus 2 or 3 Pascal fluctuations to the baseline and enclosure pressure measure­ments.)

If airtightness data at indoor/outdoor enclosure pressures that are typical of ordinary operation are desired, a multi­point regression method is used to collect and analyze the data. Typical operational enclosure pressures are in the range of 4 to 10 Pascals. At these pressure differences, wind and stack effects become a large frac­tion of the test signal. For that reason, data are collected over a large range of enclosure pressures, and linear regression analysis is applied to transformed nonlinear data. ASTM E779, Standard Test Method for Determining Air Leakage Rate by Fan

Pressurization, details this method. Figure 3 illustrates data from this kind of test.

The relationship between the test air­flow and the enclosure pressure or a range of enclosure pressures is not linear. It very nearly follows a power law, as shown by Equation 1.

)nQfan = C(∆Penclosure

Equation 1

Where: • = the measured airflow through Qfan

the test fan (or fans in the case of large buildings)

• = the change in the indoor­∆Penclosure

outdoor pressure difference induced by operation of the test fans (in this paper called the enclosure pressure)

• C = a flow coefficient that is a char­acteristic of the size and shape of the air leakage sites

• n = is the flow exponent with theo­retical limits between 0.5 and 1.0

Figure 3 – Multipoint regression method: Regression analysis on transformed nonlinear data fit to Equation 1. Air leakage at enclosure pressure less than 10 Pascals can be extrapolated using this method.

Analysis includes calculation of the flow coefficient C, exponent n, and a 95% confi­dence interval. These values allow calcula­tion of flows at the lower reference enclosure pressure of 4 Pascals and 10 Pascals, as well as the higher ones of 50 and 75 Pascals.

The following test methods and proto­cols are the most frequently used in the U.S.:

• ASTM E779-10, Standard Test Method for Determining Air Leakage Rate by Fan Pressurization

• ASTM E1827-10, Standard Test Meth-ods for Determining Airtightness of Buildings Using an Orifice Blower Door

• RESNET Chapter 8 of the National Mortgage and Housing HERS Standards

• U.S. ACE Air Leakage Test Protocol for Measuring Air Leakage in Buildings

• The Air Barrier Association of America’s (ABAA’s) Whole-Building Fan Pressure Test Committee – Stan-dard Method for Building Enclosure Airtightness Compliance Testing

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Figure 4 – Test results normalized to enclosure surface area for the 16 mid- to high-rise buildings tested in ASHRAE project 1478.

The two ASTM standards do not include many of the issues that must be addressed in order to test large, complex buildings. They don’t include acceptance criteria for determining whether or not a building meets an airtightness specification. All of the standards and protocols listed above reference one or both of the ASTM methods as the basis for collecting and analyzing data, including calculation of uncertainty. The techniques used to calculate uncer­tainty are different, depending on how the data are collected and analyzed. Calculated uncertainty is used to determine whether or not the data quality objectives have been met. Data quality objectives depend on the purpose of the test. For example, if the test is being conducted to determine whether or not an enclosure meets an airtightness specification, and the test result is close to the target, a small uncertainty interval is needed. If the test is part of a survey in which the data will be placed in a histo­gram, a larger uncertainty interval may be acceptable.

The RESNET standard allows both repeated single-point and multipoint regres­sion methods and includes acceptance cri­teria for determining whether or not a building meets airtightness specifications. It

does not address preparation of larger, more complex buildings. The ACE test protocol allows only multipoint regression, includes acceptance criteria, and addresses many of the preparation issues found in large, com­plex buildings. The ABAA Whole Building Test Committee has drafted and balloted a new standard test method, ABAA Whole-Building Fan Pressure Test Committee’s Standard Method for Building Enclosure Airtightness Compliance Testing. It allows multipoint regression and repeated single-and two-point test methods, includes accep­tance criteria, and addresses the issues found in large, complex buildings, including many not addressed by other standards.

It is useful to be able to compare test results between buildings. In order to do so, a variety of metrics have been used over the past 30 years. The most commonly used metrics for large buildings are cfm at an enclosure pressure of 75 Pascals divided by the total surface area of the test enclosure (cfm75/ft2). The surface area of the enclo­sure includes the roof, walls, and founda­tion floor. Residential programs often nor­malize by the building volume, resulting in air changes per hour at 50 Pascals (ACH50). ACH50 is the cfm at an enclosure pressure of 50 Pascals times 60 min./hr. divided by

the volume of the building. Neither of these metrics is perfect for

comparing buildings. Normalizing to the surface area makes low-rise buildings with large footprints appear more airtight than taller, more complex buildings, because the large roofing membranes and concrete floor slabs dominate. ACH50 runs into problems comparing buildings over a wide range of sizes because as size increases, surface areas and volumes change at different rates.

Figure 4 shows the results for the tests conducted during the ASHRAE 1478 research project. In this project, the build­ings were tested in pressurization and depressurization mode. The HVAC penetra­tions had fans off, dampers in the closed position, and HVAC penetrations temporar­ily sealed. The results are normalized by the enclosure surface area (top, bottom, and sides included). Figure 4 shows the results for a pressurization test, a depressurization test, and the average of the two for each building. The results ranged from a low of 0.06 cfm75/ft2 to a high of 0.74 cfm75/ft2. The average is 0.29 and the median is 0.24 cfm75/ft2. Half of the buildings in the study met the ACE’s target of 0.25 cfm75/ft2, and 75% met the GSA target of 0.40 cfm75/ft2. All of the buildings in the study were volun­teered. All of them were owner-occupied or institutional buildings. Six of the buildings had air barriers specifically included in the drawings and specifications or had an air barrier consultant as part of the design or QA team. It is suspected that the study sample is biased toward tighter buildings.

Here is an abbreviated list of codes and building programs that include whole-building fan pressure tests and their com­pliance targets:

• 2012 IECC – Continuous air barri­ers; 0.40 cfm75/ft2 enclosure is one path to compliance.

• GSA – Continuous air barriers and the enclosure is less than 0.40 cfm75/ft2 enclosure (all six sides) P100.

• ACE – Continuous air barriers, and the enclosure is less than 0.25 cfm75/ft2 enclosure (some ACE proj­ects use 0.15 cfm75/ft2).

• Passive House requires continuous air barriers, and the enclosure is less than 0.6 ACH50 (around 0.03 - 0.12 cfm75/ft2 enclosure [all six sides]).

• British code for museums and archi­

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val storage is less than 0.08 cfm75/ft2

of enclosure.

The results for the 1478 project include: • 12 buildings that meet the GSA target • 8 buildings that meet the ACE target • 5 buildings in the range to meet the

Passive House target • 1 building that meets the British code

for museums and archival storage

The following data are needed to suc­cessfully conduct tests in accordance with E779 or E1827 and normalize the results to the building surface area:

• Airflow through test fans • Inside/outside pressure difference

during baseline condition • Inside/outside pressure difference

induced by test fans • Temperature of air passing through

the test fans • Altitude of the building • Test enclosure surface area or build­

ing volume • Interior pressure differences to mon­

itor single-zone condition

TEST EQUIPMENT There are three North American manu­

facturers of test equipment for conducting whole-building fan pressurization tests. The equipment includes variable-speed test fans with integrated flow-measuring sensors, adjustable frames and panels to seal test fans into door or window openings, and electronic micro-manometers for measur­ing air pressure differences. Two of the manufacturers have developed a combina­tion of computer software and networking hardware so data can be collected from multiple micro-manometers measuring test fan air flows and enclosure pressures. The tests can be controlled from a computer, and the data are automatically analyzed in accordance with test standards. One of the manufacturers produces a large, trailer-mounted test fan capable of providing test flows equal to that of several smaller test fans. In the author’s experience, networking smaller fans provides the simplest solution for buildings with many interior partitions and less than 100,000-cfm test flows. In larger, more open buildings, the trailer-mounted fans have the advantage of a single setup location.

It is sometimes possible to test a build­ing using the ventilation fans. A depres­

surization test can be conducted using the exhaust fans in the building (with all outdoor air intakes closed or sealed). A pressurization test can be conducted using the outdoor air ventilation flows (with all exhaust outlets closed or sealed). The major barrier to this method is making accurate measurements of airflow through the venti­lation systems. In the author’s experience, this process takes far more time than using manufactured test equipment. This could be overcome in new buildings by designing the ventilation systems to conduct a fan pressure test.

SPECIFYING A FAN PRESSURE TEST

Whole-building fan pressure tests are being specified for new buildings with increasing frequency. Many of the specifica­tions crossing the author’s desk lack crucial information or include requirements that are impractical or inconsistent with other requirements. For example, the specifica­tions may not include the surface area of the test enclosure or even clearly identify the bounding walls, floors, and ceilings of the test enclosure. Some specifications pro­hibit testing on rainy days or require the testing agency to shovel snow off the roof and two feet away from the ground floor. Some require the testing agency to verify that all air barriers have been installed correctly. At the time of testing, most air barriers are covered by interior or exterior finishes.

Here is some guidance for specifying an airtightness test:

• Make it clear who hires the testing agency.

• Do not repeat or contradict items that are adequately covered in the referenced test methods.

• Include a rationale for any specifica­tion that contradicts requirements in the referenced test method.

• Provide the purpose of the test. • Require qualifications of the testing

agency. • List conditions that must be met

before the building can be tested. • List contractor and owner responsi­

bilities. • Designate test methods (E779,

E1827, ACE protocol, RESNET, ABAA).

• State the airtightness target (cfm75/ ft2 enclosure or ACH50).

• Name test enclosure boundaries. • Test enclosure surface area or build­

ing volume. • Designate treatment of HVAC pen­

etrations, trash chutes, gas meter rooms, mechanical rooms, coiling doors and dock levelers.

• List acceptance criteria (how the test result will be interpreted).

• Describe what happens if the build­ing fails.

• Include reporting requirements.

CONDUCTING A FAN PRESSURE TEST Planning

The basics of testing covered in the introduction are the same for all build­ings. The logistics, setup, and testing for large, complex buildings include many more issues than when testing single-family resi­dences. There are more people involved: owners, building management, building facilities, contracted HVAC management and maintenance, and security. The build­ing may have multiple occupants. Some areas of the building may be inaccessible for safety or security reasons (e.g., they’re not going to let you into IRS offices, banks, law offices, or the executive suite). In the case of new construction, the owner is usually the general contractor, special health and safety issues are in play, and the HVAC systems belong to the HVAC subcontractors. The HVAC systems are more numerous and more complex. Everything is bigger–more stairs to climb, more corridors to walk, more windows and doors to close and latch or block open, as well as more test equipment to move, set up, and calibrate.

Here’s a list of tasks that must be accomplished to plan a test:

• Determine whether or not it is a new, unoccupied building or an occupied building. It is much easier to test an unoccupied building than an occupied building. Access is eas­ier, and there are fewer nonpartici­pants who may accidentally interfere with data collection.

• Identify parties. Parties involved must include someone authorized to approve conducting of the test; someone who can provide access to all rooms, mechanical rooms, and safe access to all locations where HVAC-related penetrations have to be temporarily sealed; and someone

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authorized to place the HVAC equip- temporarily masked. If the inten- In practice, making the building a sealed ment into the proper status so that a tion is to test the building in a more box means closing all the doors, windows, test can be conducted and to restore operational condition, then HVAC hatches, and HVAC-related penetrations the equipment to operational status penetrations will have associated in the enclosure. Decisions must be made after the test. In some cases, secu­ fans turned off and dampers closed, about how to handle situations such as rity personnel, an air sealing crew, but they will not be temporarily mechanical rooms with doors to both the or health and safety personnel will air-sealed. The ABAA test standard interior and exterior. Should both doors be be involved. contains a relatively complete list of closed? Should the exterior door be open

• Select date. Select a date when treating HVAC equipment and relat­ and the interior door closed? Or should the there will be the fewest people in the ed penetrations; the list is included interior door be open and the exterior door building. In new buildings, this is in Table 1. Table 1 includes treat- be closed? often easier than in occupied build­ ment for coiling overhead doors, Creating an open single zone is often ings. In occupied buildings, testing trash disposal systems, and loading achieved by simply opening all the interior may be most practical during eve- dock levelers, as well as HVAC pen- doors. Some situations may create barriers nings, weekends, or holidays. etrations. to single-zone conditions:

• Identify test enclosure boundar- • Calculate how much test air is • Rooms that cannot be opened for ies. Test boundaries must be identi­ needed. How much test capacity is security reasons. Often these rooms fied and agreed to before testing. needed is fairly simple to calculate are so well-connected by ductwork Decisions must be made about how for buildings that have a test specifi­ that during testing they are within mechanical rooms, basements, crawl cation that includes an airtightness 10% of the enclosure pressure and spaces, attics, and vestibules will be target—e.g., area enclosure (ft2) x meet single-zone conditions. treated. The surface area of the test 0.25 cfm/ft2 at 75 Pascals for ACE • Portions of the building that are enclosure should be included in test projects. For other projects, the air- within the test enclosure but iso-specifications. If the surface area is tightness target per square foot of lated from the rest of the building not provided, conduct and document enclosure 0.25 cfm/ft2 at 75 Pascals by firewalls with no access doors the calculation clearly. must be replaced by the specified penetrating the firewall. These

• Identify adequate power for test target. If it is an existing building have doors opening to the outside equipment. Most test fans use with no specified airtightness tar- and can be tested simultaneously by electric motors. Each fan typically get, then the airtightness must be maintaining zero pressure difference requires a separate 115-volt, 15-amp guessed. For ordinary construction, between them and the main part circuit. 0.40 cfm75/ft2 is a good rule of of the building using separate test

• Identify areas that are not clear- thumb. If the building is experienc­ equipment. (See Figures 5 and 6.) ly inside or outside the test. ing problems associated with leaky • Ceiling or floor cavities with large Mechanical rooms, attics, and crawl enclosures, a good rule of thumb air leaks to the outside. spaces are examples of spaces that is 0.6 cfm75/ft2. Bear in mind that may or may not be inside the test some problem buildings the author The following list includes items that area. Generally, if they are vented has tested are greater than 1.5 cause problems for enclosure measurements: to the outdoors through permanent, cfm75/ft2. If it is anticipated that the • Wind pressures, especially fluctuat­nondampered openings, they are building is relatively airtight, bring ing wind pressure considered outside the test enclo­ enough fans to meet 0.25 cfm75/ft2 . • Water in tubing that connects outdoor-sure. If the air barrier systems and insulation layers enclose these spac- PREPARING THE BUILDING

enclosure pressure taps to manom­eters

es, they are considered inside the For most tests, the intention is to pre­ • Direct sunlight on long lengths of space. pare the test building so that it resembles tubes

• Identify HVAC equipment that as nearly as possible the simple box in • Small air leaks in tubing greater must be turned off, dampers that Figure 1. than 100 feet in length must be closed, and penetrations • The box is sealed except where test • Someone stepping on a tube that must be temporarily sealed. fans are inserted into door or win-How the HVAC penetrations are dow openings. Although E779 and E1827 recommend treated depends on the test’s pur­ • The interior is wide open, creating a wind speeds less than 4 mph, the introduc­pose. If the goal is to test the quality single-zone condition as far as enclo­ tion of computerized data acquisition and of design and installation of air bar- sure pressures are concerned. analysis test equipment has made it pos­rier systems in the building enclo­ • Manometers with pressure taps sible to collect data simultaneously from all sure, then all HVAC-related open- measure representative enclosure enclosure pressure and fan sensors aver­ings typically have their associated pressures. aging over longer time periods and across fans turned off, their dampers in • Test fans are placed to provide good multiple façades, providing high-quality the closed position, and outdoor air enclosure pressure distribution. data over a much wider range of wind con-and exhaust louvers and grilles are ditions. The ACE test protocol has no upper

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limit on wind speed. Place outdoor enclosure pressure taps

away from exterior corners, as close to the intersection of the exterior wall and grade as possible. Protect the open end of the tube from water (e.g., tape tubing to well with open end pointing down, and use an open vessel that shelters the tubing end from rain). Use tubing lengths less than 100 feet when possible. Check tubing for air leaks as part of quality assurance, and place tubing where it is hard for someone to step on it.

In a wide-open building, the test fans can be placed anywhere there are doors to the exterior. (Note: On windy days, do not set up a test fan on the windward side of the build­ing.) If interior walls and floors divide the building into spaces connected by a single

Figure 5 – An illustration of testing a building that is divided in two by adoor or a small number of doors, then the firewall with no openings through it. Test fans are set up in each portion of the test fans must be distributed among these building. The fans in the red-outlined portion of the building are controlled tosomewhat-isolated areas. Some examples: induce the correct enclosure pressures on the building while the test fans in the• A single entry door into an area green-outlined portion of the building are controlled to maintain zero pressurethat is closed off from the rest of difference between the two. This provides results for each section separately and the building except for a single for the overall building.door. Imagine three fans set up in

the entry door exhausting 15,000 cfm from the area induces an enclosure pressure of -75 Pascals relative to the outside. Some of the 15,000 cfm will come through the exterior walls of the area from outside, but a lot will come through the connecting door from the rest of the building. If 13,000 cfm of the air comes through the con­necting door, and 2,000 cfm comes from outdoors and leaks through the demising walls, an 18-Pascal pressure drop will be induced across the connecting door. The portion of the building outside the area with the fans will be at -58 Pascals relative to the outside. In this case, single-zone conditions will not be met.

• A six-story building in which the major air leakage site is the roof/wall connection on the sixth floor. Two stairwells with single doors to each floor connect the top five floors tothe ground floor. Test fans can only be installed on the groundfloor (short of removing a panel of glass from a curtain wallon upper floors). If 30% of the test air comes through the airleak on the sixth floor, when the rest of the building is at anenclosure pressure of 75 Pascals relative to the outside, thesixth floor may have a considerably lower enclosure pressure.Single-zone conditions are not maintained.

Creating a single-zone test condition in large, complex build­ings is something that cannot be taken for granted. For that reason, the ACE and ABAA test standards require that pressure differences between the area where the test fans are located, and Figure 6 – Two separate zones tested as one building. The portions of the building separated by walls or floor with few inte- first zone is the ground floor and is shaded in purple. rior door openings in them must be measured. This allows single- The second zone consists of the unshaded floors—the zone conditions to be verified. For these standards, single-zone condi- basement and the second through the sixth floor. There tions mean that the pressure difference between interior zones must are no intentional openings between the two zones. A test be less than 10% of the enclosure pressure. (See Figures 5 and 6.) fan is located in each zone, and zero pressure difference is

maintained between zones during the test.

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MORE ON HVAC PENETRATIONS Preparation for the HVAC-related open­

ings in the building should be in accordance with the test specification. The ABAA test standard provides guidance for two default test purposes:

• Air barrier systems enclosure test

(HVAC-related openings excluded) • Operational enclosure test (air barri­

er systems and HVAC-related open­ings included)

In the first, the purpose of the test is to determine whether the installed air barrier

systems in the walls, ceilings, roofs, and foundation that form the thermal enclosure have met a specified airtightness target. The second test purpose is used if the inten­tion is to test the overall airtightness of the buildings in a way that is more represen­tative of air leakage during more ordinary

Intentional Openings Air barrier systems Operational enclosure enclosure test (HVAC-related test (air barrier systems openings excluded) and HVAC-related

openings included)

Doors, hatches, and operable windows inside the test enclosure Open Open Fire dampers Remain as found Remain as found Windows, doors, skylights, and hatches in the bounding enclosure Closed and latched Closed and latched Windows, doors, hatches, and operable windows in ancillary spaces Treat in accordance Treat in accordance as identified in section 10.6.3 with 10.6.3 with 10.6.3 Dryer doors and air-handler access panels Closed and latched Closed and latched Vented combustion appliance Off, unable to fire Off, unable to fire Pilot light As found As found Chimney or outlet for vented combustion device in a separate As found As found mechanical room B-vent or other insulated chimney serving a vented combustion Sealed* As found appliance located within the test enclosure Solid fuel appliances (fireplaces, wood-burning stoves, pellet stoves) No fires; dampers closed; No fires; dampers closed

chimney sealed* Exhaust, outdoor air, make-up air fans, air handlers that serve Off Off areas inside and outside the test enclosure Clothes dryers Off Off Air intake inlet with motorized dampers Dampers closed and sealed* Dampers closed Air intake inlet with gravity dampers Sealed* As found Air intake inlet with no dampers Sealed* Open unless fan(s) serving

inlet is operated >8000 hrs./year, then sealed*

Exhaust or relief air outlet with motorized dampers Dampers closed and sealed* Dampers closed Exhaust or relief air outlet with gravity dampers Sealed* As found Exhaust or relief air outlet with no damper Sealed* Open unless fan serving

outlet is operated >8,000 hours/year, then sealed*

Active or passive smoke control systems – air reliefs and intakes Sealed* As found Intended powered or nonpowered openings for vented Sealed* As found shafts/stairwells Waste or linen handling systems and equipment Sealed* at rooftop chute Rooftop chute vent open,

vent opening. chute intake doors closed, chute intake room and chute discharge room doors closed and latched, fire dampers left as found

Clothes dryer outlets Sealed* As found; sealed* if dryers are not yet installed

Exhaust, outdoor air, or make-up air fan that runs >8,000 hours per yr. Sealed* Sealed* Ductwork that serves areas inside and outside the test enclosure Sealed* at supply and return Sealed* at supply and

return Floor drains and plumbing Traps filled Traps filled

*Sealed means that an opening has been temporarily masked airtight (e.g., covered with self-adhering plastic film, taped polyethylene film, or rigid board stock). See Annex A. Also see article 10.12.4.

Table 1 – Default conditions for building preparation.

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operating conditions. Table 1 from the ABAA

standard is shown herein. It includes the HVAC-related penetrations, the operation­al status of certain HVAC equipment, treatment of doors and windows in the test enclosure, treatment of doors and hatches inside the test enclosure, treatment of some specialized spaces that are isolated from the test enclosure (e.g., trash convey­ance and compaction sys­tems), and HVAC systems that serve the test enclosure and zones outside the test enclosure.

The ASHRAE 1478 proj­ect used a simple test proce­dure to estimate the air leak­age through HVAC-related penetrations. The HVAC pen­etrations were prepared by turning off the exhaust and make-up air fans, closing all the outdoor air and exhaust air dampers, and temporarily sealing all the HVAC pen­etrations. The building’s enclosure pres­sure was then held at 75 Pascals, and a baseline with HVAC penetrations sealed was collected. Next the HVAC penetra ­tions were unsealed (but motorized damp­ers remained closed; gravity dampers may have been drawn closed or blown open), and undampered openings (e.g., kitchen range exhaust) become open holes. The results of these simplified measurements are shown in Figure 7.

THINGS THAT CAN GO WRONG DURING A TEST

This is an abbreviated list of things that can go wrong during a test. (Note: At this point, the author fervently hopes he has listed every conceivable error. However, this list does not include the really dumb stuff, like forgetting the fan controllers, going to the wrong building, or conducting a test with a window on the sixth floor open.)

• An entry door, a gravity damper, or masking on an HVAC-related open­ing may blow open during a pressur­ization test. Catch this by noticing that the test result is changing.

• Someone may open a door or stand

Figure 7 – The triangles are test results with HVAC penetrations sealed, and the dots are with the HVAC penetrations unsealed. In some buildings, it makes a significant difference; while in others, it makes almost no difference.

Figure 8 – Depressurization and pressurization curves for a building with a large gravity damper blowing open during the pressurization test.

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on a tube during the test. This is obvious if continuous monitoring is taking place on-screen or if a data point is automatically rejected by internal software quality assurance.

• An interior door may be blown closed, changing the test boundar­ies partway through a test (noted by change in the sound of the fans’ flow or enclosure pressure data).

• Heavy wind or rain can make a test impractical (pretty obvious).

The building depicted in Figure 8 was tested in depressurization first. The data have a small 95% confidence interval and fit the power curve well. The lowest three pres­surization data points match the depressur­ization data points well. However, each suc­ceeding pressurization data point increas­ingly deviates from the depressurization result. The building is getting progressively more leaky. This is typical of what it looks like when an entry door is unlatched and the pressure in the building is prevent­ing it from closing completely. As the test pressure increases, the door opens further but not all the way because the door closer provides resistance. A large gravity damper and self-adhering duct mask blowing off and HVAC louver also appear the same way.

INTERPRETING RESULTS How test results are interpreted depends

on the purpose of the test. If one is testing to determine whether or not a building meets an airtightness specification, a test can return one of three results:

• It clearly passes. • It clearly fails. • I can’t tell.

It is, of course, the “I can’t tell” result that causes problems. The situation where the smallest confidence interval is the best is when the test result is within the uncer­tainty of the measurement. No matter how small, acceptance criteria must be used to determine whether it is a pass or a fail.

ACE and ABAA test protocol specify: • Calculate 95% confidence intervals

(in accordance with test method) — Pass: If test result ≤0.25 cfm75/

ft2 and 95%CI ≤ 8%: — If test result ≤0.25 cfm75/ft2 and

95%CI > 8%:

• Pass: If test result + 95%CI ≤ 0.25 cfm75/ft2

• Fail: If test result + 95% CI > 0.25 cfm75/ft2

— Fail: If test result >0.25 cfm75/ ft2

• ABAA allows failing a building if the specified airflow produces less than 75% of the reference test pressure.

None of the standards include accep­tance criteria if the test is being done to compare to other buildings or to compare a post-airtightening test to a pre-airtightening test. Criteria would need to be developed to meet the needs of each project.

REPORT A test report should include, at mini­

mum, the following items: • Date • Weather conditions • Building testing agency • Building description • Test target • Test results • Location of test equipment • Identification of test enclosure

boundaries • Test configuration of each intention­

al opening in the building enclosure • Test environmental conditions • Any departures from test standard

or specifications • Measured test results in tabular

form • Conclusions and recommendations

FINDING THE BIG AIR LEAKS There are a number of methods used to

find air leaks in buildings. Several of these methods are described in ASTM E1186, Standard Practices for Air Leakage Site Detection in Building Envelopes and Air Barrier Systems. Many of them depend on operating a building under negative or positive pressure. As such, after a whole-building pressure test has been conducted, it is a good time to seek the leaks. The meth­ods include:

• Listen—Some air leaks whistle, buzz, flap, or whoosh when the building is pressurized or depressurized.

• Use your skin to feel for air leaks when depressurizing. — Stand in stairwell doorways at

each floor: The floors with the greatest breeze have the largest leaks.

— Stand at the ends of corridors where wings join other parts of the building.

• Use chemical smoke bottles or theat­rical fog to track air flows.

• Use infrared scanners when there is a large enough indoor/outdoor temperature difference to identify air leaks.

Using these techniques, the author has found that the largest air leaks in large buildings occur where enclosure systems meet but don’t connect. This is the order of most commonly encountered large leaks:

• Where roofs meet walls at the top of the building

• Where lower roofs meet walls that rise above them

• Where there are exterior soffits beneath lower walls, canopies, and plazas

• Where walls meet foundations • Where utility shafts connect two or

more of the above items

CONCLUSIONS Using modern test equipment, it has

become practical to conduct fan pressuriza­tion tests on large, complex buildings. A final whole-building airtightness test will:

• Document compliance or failure to comply with an airtightness specifi­cation

• Provide induced pressure difference to aid in finding remaining air leaks (E1186)

• Provide motivation to effectively install air barrier assemblies and identify air leakage sites not detailed in drawings and specifications dur­ing construction

• Not otherwise make buildings more airtight

REFERENCES Wagdy Anis, 2014, “ASHRAE 1478-RP,

Measuring Airtightness of Mid- and High-Rise Nonresidential Buildings Research Results and Conclusions,” WJE, 2014.

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