Building Envelope & Air Barrier

Facility Commissioning Group offers building envelope commissioning and diagnostic services utilizing national standards and guidelines.  Our staff is managed by an Indiana Registered Architect from our Indianapolis Branch Office.  FCG offers comprehensive building envelope commissioning and diagnostic services utilizing ASTM Standards and the NIBS Whole Building Design Guide to include exterior enclosures air barrier commissioning, air leakage testing by door blower fans, thermography, spray testing and smoke testing.

“This owner advocacy service benefits the project by providing a third party consultant to review the building documents and observe and document construction methods and specified testing requirements that assure the building design and installation satisfies to the owner’s project requirements.”

NIBS Guideline 3 Exterior Enclosures Commissioning is a defined quality assurance process for verifying proper installation of systems separating the interior environment from the outdoor environment, including exterior walls, fenestration, doors, windows, roofing, roof openings, below grade perimeter walls and the slab-on-grade or crawlspace. This verification process is carried out during construction to assure compliance by installers with the design intent. This owner advocacy service benefits the project by providing a third party consultant to review the building documents and observe and document construction methods and specified testing requirements that assure the building design and installation satisfies to the owner’s project requirements.

ISO 6781-1983 is a standardized Thermographic examination for detecting thermal irregularities in the building envelope. This test is often applied after other techniques determine excessive building air leakage. The benefit to the owner for this testing involves defining where there are building construction issues that require closer physical examination and construction mitigation efforts, as well as establishing a baseline for evaluating mitigation work.

ASTM C 1060 is a guide to the proper use of infrared imaging systems for conducting qualitative thermal inspections of building walls, ceilings, roofs, and floors, framed in wood or metal, that may contain insulation in the spaces between framing members. This procedure allows the detection of cavities where insulation may be inadequate or missing and allows identification of areas with apparently adequate insulation. Although infrared imaging systems have the potential to determine many factors concerning the thermal performance of a wall, roof, floor, or ceiling, the emphasis in this practice is on determining whether insulation is missing or whether an insulation installation is malfunctioning. Anomalous thermal images from other apparent causes may also be recorded as supplemental information, even though their interpretation may require procedures and techniques not presented in this practice.

ASTME E-779 (2003) is a standardized test method for measuring air-leakage rates through a building envelope under controlled pressurization and depressurization using fans, either permanent equipment, portable blowers, or a combination of fans. The methodology allows for a mathematical characterization of exterior enclosure leakage rates to evaluate the constructed sealed condition. Air infiltration and/or exfiltration of conditioned space accounts for a significant portion of the thermal space conditioning load. The benefits to the building owner are confirmation of good construction standard of exterior enclosures, HVAC energy savings, a cleaner environment for the occupants and reduced introduction of outside pollutants, moisture, and drafts caused by undetected envelope air leakage.

ASTM-E 1186-09 techniques for air leakage site detection covered in these practices allow for a wide range of flexibility in the choice of techniques that are best suited for detecting various types of air leakage sites in specific situations.  The infrared scanning technique for air leakage site detection has the advantage of rapid surveying capability. Entire building exterior surfaces or inside wall surfaces can be covered with a single scan or a simple scanning action, provided there are no obscuring thermal effects from construction features or incident solar radiation. The details of a specific air leakage site may then be probed more closely by focusing on the local area. Local leak detection is well addressed with the smoke tracer, anemometer, sound detection, the bubble detection, and the tracer gas techniques, however these techniques are time consuming for large surfaces. The pressurized or depressurized test chamber and smoke tracer or a depressurized test chamber and leak detection liquid practices can be used in situations where depressurizing or pressurizing the entire envelope is impractical, such as is the case during construction. Both of the practices enable the detection of very small leaks. To perform these practices requires that the air barrier system be accessible.  Complexity of building air leakage sites may diminish the ability for detection. For example, using the sound detection approach, sound may be absorbed in the tortuous path through the insulation. Air moving through such building leakage paths may lose some of its temperature differential and thus make thermographic detection difficult. The absence of jet-like air flow at an air leakage site may make detection using the anemometer practice difficult.  Stack effect in multistory commercial buildings can cause gravity dampers to stand open. Computer-controlled dampers should be placed in normal and night modes to aid in determining the conditions existing in the building. Sensitive pressure measurement equipment can be used for evaluating pressure levels between floors and the exterior. Monitoring systems in high-tech buildings can supply qualitative data on pressure differences.

ASTM E 1677 covers the minimum performance and acceptance criteria for an air barrier (AB) material or system for framed walls of low-rise buildings with the service life of the building wall in mind. The provisions contained in this specification are intended to allow the user to design the wall performance criteria and increase AB specifications to accommodate a particular climate location, function, or design of the intended building. This specification focuses mainly on ABs for opaque walls. Other areas of the exterior envelope, such as roofs, floors, and interfaces between these areas are not included in this specification. Also not addressed here are air leakages into the wall cavity, that is, windwashing. Additionally, the specifications in this standard are not intended to be utilized for energy load calculations and are not based on an expected level of energy consumption.ASTM E 1827 – Standard Test Methods for Determining Airtightness of Buildings.

ASTM E 2178 procedures measure the air permeance of flexible sheet or rigid panel-type materials. The results of this test may be useful in determining suitability of that material as a component of an air retarder system.  This method does not address the installed air leakage performance of building materials. The installed performance of air retarder materials and air retarder systems in low-rise framed wall construction is addressed in Specification E1677.  This test method is to determine the air permeance of building materials at various pressure differentials with the intent of determining an assigned air permeance rate of the material at the reference pressure difference (ΔP) of 75 Pa.  The method is intended to assess flexible sheet or rigid panel-type materials using a 1 m × 1 m specimen size.  The values stated in SI units are to be regarded as standard. No other units of measurements are included in this standard.

NISTIR 7238 a simulation study of the energy impact of improving envelope airtightness in U.S. commercial buildings. Despite common assumptions, measurements have shown that typical U.S. commercial buildings are not particularly airtight. Past simulation studies have shown that commercial building envelope leakage can result in significant heating and cooling loads. To evaluate the potential energy savings of an effective air barrier requirement, annual energy simulations were prepared for three nonresidential buildings (a two-story office building, a one-story retail building, and a four-story apartment building) in 5 U.S. cities. A coupled multizone airflow and building energy simulation tool was used to predict the energy use for the buildings at a target tightness level relative to a baseline level based on measurements in existing buildings. Based on assumed blended national average heating and cooling energy prices, predicted potential annual heating and cooling energy cost savings ranged from 3% to 36% with the smallest savings occurring in the cooling-dominated climates of Phoenix and Miami. In order to put these estimated energy savings in context, a cost effectiveness calculation was performed using the scalar ratio methodology employed by ASHRAE SSPC 90.1.