ASHRAE Journal - July 2020 - 61

FIGURE 18 Wood frame assembly with exterior insulation and interior cavity insulation with brick or stone veneer and a smart interior vapor control layer or kraft-faced cavity insulation.

Applicability
OK Marine, cold, very cold and colder hygrothermal regions.
OK All rain exposure zones and interior climate Classes I and II.
NO Interior climate Class III buildings such as hospitals, museums and swimming pool enclosures.
Description This wall is a variation of Figure 17, but with a variable permeance ("smart") vapor control
layer or kraft-faced batt insulation (also a "smart" vapor control layer). This wall is designed to dry to the
interior. The sheathing can be non-paper-faced exterior gypsum, plywood, fiberboard or oriented strand
board.
Drainage Cavity Hydrostatic pressure is controlled by providing a drainage space behind the cladding.
The ideal solution is to decouple the exterior brick veneer (a "reservoir" cladding) from the wall assembly
with a ventilated and drained cavity. The cavity behind the brick veneer should be at least 1 in. (25 mm)
wide and free from mortar droppings. It must also have air inlets ("weep holes") at its base and air
outlets ("weep holes") at its top to provide back ventilation of the brick veneer.
Exterior Insulation Vapor permeable (mineral wool or rigid fiberglass insulation) required.
Water Control Layer Combined air/vapor/water control layer at the exterior sheathing. Can be fully
adhered sheet membrane, trowel-on or spray-applied coating, mechanically attached sheet or integral
water control layer within the sheathing.
Air Control Layer Combined air/vapor/water control layer at the exterior sheathing.
Vapor Control Layer (Exterior) Combined air/vapor/water control layer at the exterior sheathing.
The vapor control layer is vapor permeable. Where the annual average rainfall exceeds 20 in. (508 mm)
and a reservoir cladding such as brick or stone veneer is used, the vapor control layer should be vapor
semipermeable (or less in permeance) to control inward vapor drive.
Vapor Control Layer (Interior) and Condensation Control This wall assembly has a variable
permeance ("smart") vapor control layer or kraft-faced batt insulation (also a "smart" vapor control
layer). This layer changes its vapor transmission based on interior relative humidity. It, therefore, allows
inward drying during the summer or if the wall cavity becomes wet from exterior sources. Even with
inward drying, this wall assembly should be limited to interior climate Class I and II buildings. Despite the

effectiveness of the variable permeance interior vapor control layer, this wall assembly should
still be limited to marine, cold, very cold and colder hygrothermal regions.
Thermal Control Layer Stud bay cavity insulation and exterior rigid insulation.

FIGURE 19 Wood frame assembly with exterior insulation and interior cavity insulation with synthetic stucco (EIFS).

Applicability
OK All hygrothermal regions except subarctic/arctic.
OK All rain exposure zones and interior climate Classes I and II.
NO Interior climate Class III buildings such as hospitals, museums and swimming pool enclosures.
Description This is a water-managed exterior insulation finish system (EIFS) wall. Unlike "face-sealed"
EIFS, this wall has a water control layer inboard of the exterior stucco skin that is drained to the exterior.
It is also a flow-through assembly that can dry to both the exterior and the interior.
Drainage Cavity This wall assembly requires a drainage space between the exterior rigid insulation
and the water control layer. This can be accomplished by installing vertical beads of adhesive to adhere
the exterior rigid insulation to the sheathing.
Exterior Insulation Vapor semipermeable (expanded polystyrene/EPS) required.
Water Control Layer Combined air/water control layer at the exterior sheathing; fluid applied
membrane compatible with EIFS system adhesive.
Air Control Layer Combined air/water control layer at the exterior sheathing.
Vapor Control Layer (Interior) and Condensation Control This wall assembly does not have an
interior vapor control layer (Class III latex paint only); therefore, the thermal resistance of the exterior
insulation to avoid condensation is specified in Table 3. This wall assembly is also limited to interior
climate Class I and II buildings. In hot-humid climates, any moisture that condenses on the exterior side
of the water control layer will be drained to the exterior.
This assembly can dry inward. Therefore, vapor-impermeable and vapor semi-impermeable interior
finishes such as vinyl wall coverings, epoxy paints and alkyd paints should be avoided.
Thermal Control Layer Stud bay cavity insulation and exterior rigid insulation.

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ASHRAE Journal - July 2020

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