ASHRAE Journal - July 2020 - 60

FIGURE 16 Wood frame assembly with exterior insulation and interior cavity insulation with brick or stone veneer and no interior vapor control layer.

Applicability
OK All 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 assembly is a flow-through assembly that can dry in both directions. 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. Alternately, in milder or
lower-rainfall climates, a ¼ in. (6.4 mm) drainage mat or drainable insulation can be substituted for the
1 in. (25 mm) air cavity. This option should not be used in IECC Climate Zone 5 and higher, with rainfall
over 20 in. (508 mm) per year (due to freeze-thaw risks).
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 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.

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.

FIGURE 17 Wood frame assembly with exterior insulation and interior cavity insulation with brick or stone veneer and an interior vapor control layer.

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 16, but with an interior vapor control layer. 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 Although this wall assembly includes an
interior vapor control layer, the recommended construction uses thermal resistance of exterior insulation
to control condensation, as specified in Table 3. This wall assembly is also limited to interior climate
Class I and II buildings.
This wall assembly has an interior vapor control layer; therefore, the wall assembly cannot dry to the
interior. However, this wall assembly can dry to the exterior. Because of the interior vapor control layer,
this wall assembly should be limited to cold, very cold and colder hygrothermal regions.
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Thermal Control Layer Stud bay cavity insulation and exterior rigid insulation.

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ASHRAE Journal - July 2020

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