Installed Insulation R-value: The framed portion of this wall assembly typically has an R-value
of R-19-20 when insulated with ? berglass batt or cellulose. Exterior insulation for EIFS is
typically EPS at R-4/inch.

Whole-wall R-value: Using two dimensional heat ? ow analysis with thermal bridging effects and
average framing factors demonstrates improvements in the ef? ciency of the ? berglass batt or
cellulose in the stud space by decreasing the thermal bridging effects of the framing and the
rim joist. Adding 4” of EPS insulation for a total an increase of R-16 increases the Clear-wall
R-value of standard construction by slightly more than R-16 because of thermal bridging of
the framing and rim joist. The whole-wall R-value for this system is approximately R-30.
1

Air Leakage Control: Fiberglass batt, blown and sprayed cellulose are all air permeable materi-
als allowing possible air paths between the interior and exterior as well as convective looping
through the material. The air tightness of an EIFS system is typically at the surface of the
exterior sheathing (usually glass-faced exterior gypsum) because it is the drainage plane.
Typical Insulation Products: EPS exterior insulation, ? berglass batt, blown cellulose, sprayed
cellulose.

DURABILITY Rain Control: In the EIFS system, it is critical to correctly detail the drainage plane to adequately handle rain. Historically EIFS were constructed using a face- sealed approach, but this lead to many moisture related durability issues. EIFS can be used as part of a very durable and reliable enclosure system, provided it is drained and ventilated. Intersections, windows, doors and other penetrations must be detailed to prevent the penetration of rain water.2 Air Leakage Control: By adding exterior insulation as part of the EIFS construction, the temperature of the sheathing (condensation plane) increases, and the risk of air leakage condensation is reduced. It is always good practice to build airtight enclosure systems, often with both an interior and exterior air barrier to avoid air leakage condensation and windwashing. Air leakage condensation is one of the greatest causes of premature building enclosure failure. An air barrier should be stiff, continuous, durable, strong, and impermeable.3 Air need not leak straight through an assembly to cause moisture problems; it can also leak from the inside, through the wall, and back to the inside. Condensation within the stud space is possible if this type of airfl ow occurs, depending on the weather conditions. Hence, wall designs should control air- fl ow into the studspace.4 Vapor Control: By adding exterior insulation as part of the EIFS construction, the temperature of the sheathing (condensation plane) increases, and the risk of moisture vapor condensation is reduced. It may be possible to avoid the use of an interior vapor control layer, or use a higher permeance vapor control layer (Class II or III) depending on the amount of insulation on the exterior and regional building codes. Installing the incorrect vapor control layer or installation in the incorrect location can lead to building enclosure failure.5 Drying: Insulating sheathing limits the drying to the exterior, and the wall must be able to dry to the interior. Poly vapor barriers are typically avoided so that this drying can occur. The minimum level of vapor control on the interior surface is determined by the IRC. Installing vapor control on both sides of the enclosure will seal any moisture into the stud space, resulting in low drying potential, and possibly resulting in moisture-related durability risks. Ventilation behind vapor impermeable claddings and interior components (e.g. kitchen cabinets) can encourage drying.. …

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