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Recent research has shown that U.S. commercial and institutional buildings are not as airtight as assumed, and that envelope air leakage has a significant impact on energy consumption and indoor air quality in these buildings. This applies to all building ages, sizes, and constructions.

ONLINE TECHNICAL INFORMATION AND RESEARCH:

• Online Calculator in US Units or Metric Units for computing the parameters of large building air leakage tests.
• Airtightness of Commercial Office Buildings in the US 2005 by Emmerlich and Persily (57kb pdf format).
• Investigation of the Impact of Commercial Building Envelope Airtightness on HVAC Energy Use 2005, NISTIR 7238, by Emmerlich, McDowell and Anis (335kb pdf format).
• Impact of Infiltration on Heating and Cooling Loads in US Office Buildings 2005 by Emmerlich, Persily and McDowell (567kb pdf format).
• March 2006 ATTMA test standard: Technical Standard 1: Measuring the Air Permeability of Building Envelopes (412kb pdf format).
• Air Leakage general background information on large building air leakage (from a UK perspective).
• Airtightness of Commercial and Institutional Buildings: Blowing Holes in the Myth of Tight Buildings, 1999, Persily, NIST.
• Myths About Building Envelopes, 1999, Persily, NIST. (poor copy, missing figures)
• Energy Impacts of Infiltration and Ventilation in U.S. Office Buildings Using Multizone Airflow Simulation, 1998, Emmerich et. al., NIST.
• Energy Impacts of Air Leakage in U.S. Office Buildings, 1995, VanBronkhorst et. al., NIST.
• Workplan to Analyze the Energy Impacts of Envelope Airtightness in Office Buildings, 1995, Emmerich et. al., NIST.
• CMHC recommendation to Seal Air Leakage Paths when renovating or maintaining buildings.
• BSRIA reports on airtightess testing

ASSOCIATIONS AND MEETINGS

• New UK organization: Air Tightness Testing and Measurement Association (ATTMA)
• Air Infiltration and Ventilation Centre technical support for research and information dissemination.
• BETEC Building Environment & Thermal Envelope Council. (annual symposium)
• ICBEST International Conference on Building Envelope Systems and Technologies 2001.

EXAMPLES OF LARGE BUILDING TESTS

• April 2003 test of a 9,000,000 ft³ (256,000 m³) food distribution warehouse in Manchester, UK.

TEST METHODS AND SOFTWARE:

• New test standard from ATTMA: Technical Standard 1: Measuring the Air Permeability of Building Envelopes
• online calculator for computing the parameters of large building air leakge tests.
• ASTM E779-99 Standard Test Method for Determining Air Leakage Rate by Fan Pressurization.
• ASTM E1827-96 Standard Test Methods for Determining Airtightness of Buildings Using an Orifice Blower Door.
• ASTM E741-00 Standard Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution.
• CAN/CGSB 149.15-96 Determination of the overall envelope airtightness of buildings by the fan pressurization method using the building's air handling systems.
• CAN/CGSB-149.10-M86 Determination of the Airtightness of Building Envelopes by the Fan Depressurization Method.
• CIBSE-T23 Technical Memoranda: Testing buildings for air leakage (new UK fan pressurization test method for large buildings).
• NIST Multizone Modeling software for analyzing large building air leakage.

AIRTIGHTNESS RECOMMENDATIONS:

The U.S. has not made any significant changes in building envelope construction recommendations based on the latest airtightness research results. The UK is now more advanced in their recommendations.

• ASHRAE Fundamentals Handbook, 1997, 25.19:
  The envelopes of commercial buildings are often thought to be quite airtight. For commercial buildings, the National Association of Architectural Metal Manufacturers recommends infiltration rates per unit of exterior wall not to exceed 0.06 cfm/sf at a pressure difference of 0.30 in. of water exclusive of leakage through operable windows. Tamura and Shaw (1976a) found that air leakage measurements in eight Canadian office buildings ..... ranged from 0.120 to 0.430 cfm/ft2 (2.2 to 7.8 m3/h*m2). Other measurements taken by Persily and Grot (1987) in eight U.S. office buildings ranged from 0.213 to 1.028 cfm/ft2 at 0.30 in. of water (3.9 to 18.7 m3/h*m2 at 75 Pa). Therefore office buildings are leakier than expected. Typical air leakage values per unit wall area at 0.30 in. of water are 0.10, 0.30 and 0.60 cfm/ft2 (1.8, 5.5 and 10.9 m3/h*m2 at 75 Pa) for tight, average and leaky walls, respectively (Tamura and Shaw 1976a).
  ....air leakage in buildings is due not only to windows and doors, but to a wide range of unexpected and unobvious construction defects. Many important leakage sites can be very difficult to find.
  

  This is an excellent condensation of airtightness research up to 1997.

• EPA Energy Star is one of the few U.S. government programs that make airtightness recommendations for large buildings. Unfortunately it repeats the myths about buildings airtightness. EPA misinterprets the 1997 ASHRAE Fundamentals Handbook airtightness recommendations to suggest that a target of 0.06 cfm/sf @ 0.3"wc (1.1 m3/h*m2 @ 75 Pa) is reasonable in the Energy Star publication Building Upgrade Manual. See pages 8-10 of the Building Envelope section of the Energy Star Stage Two, Building Tune-Up. ASHRAE only quoted this NAAMM airtighness recommendation to show that it was unrealistic given the current state-of-the-art in U.S. building construction. Note that this recommended airtightness is more than 25 times tighter than the average of recent airtightness measurements of U.S. commercial and industrial buildings reported by Persily! Since the Energy Star program does not mention testing, there is little chance that the wide divergence between recommmended and actual airtightness would ever be identified. In addition, the Energy Star building envelope tune-up guidance centers on windows, doors and insulation defects and not the "unexpected and unobvious construction defects" identified as the main problem by the ASHRAE Fundamentals.

  Energy Star needs to update its building airtightness tune-up recommendations.

• Airtight buildings: meeting the Part L challenge article by BRE about new UK regulations that require airtightness testing of new buildings.
• CIBSE-T23 Technical Memoranda: Testing buildings for air leakage (lists UK recommended airtightness levels).

FAN PRESSURIZATION TEST EQUIPMENT FOR TESTING LARGE BUILDINGS:

Several large fan pressurization test systems have been built by research organizations in Canada and the UK. Recently Infiltec and Building Sciences Limited developed the next generation of fan pressurization test equipment for large buildings:

• Stacked Blower Door: Infiltec manufactures a stacking system for mounting 3 blower door fans in a single door of a building. Each fan can produce a calibrated variable flow of up to 6,000 cfm (2.85 m3/s). When 3 doors are used, the maximum flow from the 9 blower door fans is over 50,000 cfm (24 m3/s) @ 0.04 to 0.30"wc (10 to 75 Pa) building pressure. These fans are powered by the building electrical power, and a dual-sensor digital micromanometer is used to measure pressure and flow. The pressure and flow calibration are in both metric and US units. See Prices and Specifications. For more information, Email: Infiltec Factory or Call: (540) 943-2776 in Waynesboro, VA from 7AM to 4PM ET.
  
  
  
  
  

• G54 Mobile Gasoline-Powered Calibrated Fan: The Infiltec G54 mobile fan has a calibrated air-flow of over 55,000 cfm (26 m3/s) @ 0.30"wc (75 Pa). The G54 can be trailer mounted for portability, and it is powered by a built-in gasoline engine. No external power is required. The fan air flow can be varied and measured within 5% accuracy over the range of 15,000 to over 60,000 cfm (7 to 29 m3/s) @ 0.04 to 0.3 inch wc (10 to 75 Pa) building pressures. The fan is connected to the building by a durable 60" (1.5 m) diameter by 250" (6.5 m) long flex duct. Fan flow and building differential pressure measurements are displayed on built-in analog gauges, or they can be measured with a custom calibrated dual-sensor digital micromanometer. The building pressure and fan flow measurements are displayed in both metric and US units. Pictures of the G54 in use can be seen in an April 2003 test of a 9,000,000 ft³ (256,000 m³) food distribution warehouse in Manchester, UK. See Specifications and Prices. For more information, Email: Infiltec Factory or Call: (540) 943-2776 in Waynesboro, VA 7AM to 4PM ET.

For further assistance, call Infiltec at (540) 943-2776 Or Email Infiltec Factory .