Air leakage/continuous air barrier requirements. Both the 2012 IECC and ASHRAE 90.1-2010 recognize the significant impact that unwanted air infiltration has on a building's energy performance. It has been well proven that air leaks and drafts that occur around wall openings, penetrations, joints, transitions, and other common building elements add up quickly to become the equivalent of leaving a window or door open in a conditioned space. The code and 90.1 each address this issue and mandate that certain things be done; however they vary in their approach. ASHRAE 90.1 requires the general sealing of joints, seams, and material transitions throughout the building. It identifies exterior sheathing with sealed joints as an approved air barrier “material” in this case. The IECC includes the same air sealing requirements but goes beyond to specifically require a continuous air barrier be included in the exterior wall system in all but the three warmest climate zones. To demonstrate compliance, this air barrier must be tested based on any one of three options:

A. The material itself can be tested to meet an air permeability rating (≤ 0.004 cfm/ft² @ 75 Pa pressure per ASTM E 2178).

B. A full wall assembly can be tested to show an average air leakage (≤ 0.04 cfm/ft² per ASTM E 2357, 1677 or 283).

C. The entire building can be tested after it is constructed and show an average air leakage (≤ 0.40 cfm/ft² per ASTM E 779).

Regardless of the compliance path selected, the intent is the same—reduce air infiltration in buildings to an acceptable level. Further, the means to do so must be designed to withstand positive and negative pressures and stack effect pressures.

Metro Career Academy

Project: Metro Career Academy, Oklahoma City, Oklahoma Architect: Quinn & Associates, Oklahoma City, Oklahoma General Contractor: CMS Willowbrook, Oklahoma City, Oklahoma EIFS Applicator: DMG Masonry, Arlington, Texas EIFS Type & Finish: Engineered drainage system with specialty brick and limestone finish It is not an overstatement to say that clay brick masonry is the foundation of modern Oklahoma City. The look of brick and stone masonry continues to be very popular with area architects and building owners everywhere. However, the ever-increasing demands of climbing construction costs, energy efficiency, and life-cycle performance led architect Fred Quinn of Quinn & Associates to research different materials to meet the demands of this high-performance facility. The original design of the Metro Career Academy (MCA) building called for 24,000 square feet of clay brick and 13,000 square feet of cast stone. When Quinn learned that he could use an EIFS with the same look and save nearly 50 percent in construction costs (materials and installation) versus the clay brick and stone, it was an easy decision. In addition to this dramatic reduction in cladding costs, making the decision to switch to EIFS during the schematic design phase allowed the owners of the Metro Career Academy to harvest the full range of benefits from the lightweight cladding, including less structural support required, a reduced construction schedule, LEED points, projected energy savings, and fewer delivery trucks, i.e. reduced environmental impact. By substituting the 1.5 pound per square foot adhesively attached moisture drainage EIFS for the labor-intensive 40+ pounds per square foot masonry and stone, the designer was able to subtract more than 96 percent of the anticipated weight of the building’s skin. Eliminating 1,424,500 pounds from the exterior walls of the building produced additional savings in the concrete and steel support system required to carry that initially designed load. Cris Callins, manager of preconstruction with CMS Willowbrook, estimated that the reduced demand for structural support and the more rapid installation of the EIFS allowed her project manager to cut a full 15 weeks from the MCA building’s construction schedule, lowering manpower, equipment, and insurance costs as well as easily meeting the owner’s demanding completion date. The MCA project utilized 4 inches of exterior continuous insulation (ci) as part of the EIFS, which helped the MCA to achieve its goal of LEED Gold certification for this project. The project earned the full 10 points in the Energy & Atmosphere Credit 1 category available under LEED v2.2. The computer modeled performance anticipates an energy usage savings of 34.8 percent and an energy cost reduction of 42.8 percent annually compared to the baseline. Without taking into consideration rising costs of energy or inflation, it is possible to conservatively estimate the value of these energy savings over a 50-year life cycle of the MCA facility at more than $1.7 million. Overall, the EIFS assembly allowed the entire project team to increase the insulation value of the wall, enhance the moisture protection of the building envelope, and lower the cost of the exterior cladding, while retaining the desired look of masonry and stone. The engineered, fully tested system includes: Fluid-applied AWRB Fluid-applied flexible flashings at all transitions and wall penetration rough openings Drainage plane with weep details Exterior ci Continuous air barrier High-impact reinforced assembly Flexible aesthetic finish coat conveying original brick and stone appearance

 

IBC Chapter 26 – Foam Plastic Insulation

Certain types of foam plastic insulation have become popular in recent times because they not only provide thermal insulation, they can also provide water resistance, continuous air barrier qualities, and condensation prevention in some cases. Recognizing the growing use of foam plastic insulation in exterior wall assemblies, the code identifies three specific safety criteria that must be met. Primarily and justifiably so, the intent is to protect the building and people in the event of a fire where combustible plastic materials are present. Therefore all three of these conditions must be met when using them; however it is the third one that is usually the most significant:

A. Surface-burning characteristics are the first set of criteria including a maximum flame spread index and a maximum smoke developed index based on the standard ASTM E 84 test procedure. (Section 2603.3/2603.5.4)

B. Second, a 15-minute interior thermal barrier is required in order to separate the interior from the foam plastic in the event that a fire does occur. (Section 2603.4/2603.5.2). The stated acceptable thermal barrier in this case is ½-inch gypsum board or a demonstrated equivalent that will provide the needed separation.

C. Third and most important the testing of the complete exterior wall assembly is required whenever foam plastic insulation is used. (Section 2603.5.5). Under this part of the code, the specific exterior wall assembly being used must be tested in accordance with and comply with the acceptance criteria of NFPA 285. That means that any given foam plastic product needs to be tested multiple times since it is the total wall assembly, not just the foam plastic that is being tested. This requirement holds regardless of the wall classification type for commercial buildings (type I, II, III, or IV).

Note that in demonstrating compliance with these three mandatory criteria, the code does not distinguish between different types of foam plastic insulation such as polystyrene, polyisocyanurate, or urethane foam. Even though there may be differences in their make-up and manufacture, the code requires that they all must meet these three basic criteria and any other incidental criteria depending on their use.

Properly designed EIFS meet all of the building code requirements for using foam plastic insulation in exterior walls.