ARE 5.0: CE - Details

Building Envelope Purpose

1. Limit air movement and heat transfer 2. Limit moisture intrusion 3. Promote drying

Rain Screen Purpose

1. Prevent water intrusion (interrupt capillary action) 2. Allow assembly to dry (ventilation)

Rain Screen Components

1. WRB 2. Air gap 3. Ventilation 4. Cladding

Vapor Retarder Classes

1. impermeable (less than 0.1 perm) 2. semi-impermeable (0.1 - 1 perm) 3. semi-permeable (1 - 10 perms) 4. permeable (more than 10 perms) *1 & 2 considered vapor barriers

Air Barrier

A component of the building envelope that prohibits air leakage and reduces the risk of condensation. House wrap and fluid- applied air barriers are examples.

Sheathing w/ fabric WRB (Air Sealing)

Air Seal with fluid applied WRB @ punched openings, seams, penetrations

Foundation to Sheathing (Air Sealing)

Air Seal with joint and seam sealant tape (prevent wood to concrete contact)

Sheathing w/ Integral WRB (Air Sealing)

Air Seal with sealant at all joints / penetrations AND fluid applied membrane inside punched openings

Sheathing w/ Fluid Applied WRB (Air Sealing)

Air seal with fluid applied WRB @ punched openings, seams, penetrations, and over entire surface

Vapor Barrier

Building envelope component that blocks vapor movement. Recommended in climates where average outdoor temperature in January is below 40F and indoor relative humidity is 45% or more at 68F. Should be placed on the cold side of the wall to allow the assembly to dry, but the temperature at its placement in the wall assembly should be warmer than the dew-point temperature to prevent condensation when vapor gets too cold.

capillary action

Type of moisture intrusion that occurs when liquid water wicks (like a straw) into the tiny cracks and open spaces of porous building materials such as masonry block, concrete, or wood

Flashing (locations)

Locate at: 1. Horizontal joints between different exterior finishes 2. Cladding offsets, changes in substrate, or penetrations 3. Concentrated stresses (i.e. room joists, foundation joints) 4. Where drainage is compromised 5. Top / Bottom of all openings and penetrations

hydrostatic pressure

Pressure that forces water in through cracks in foundation walls and openings caused by expansion and contraction of the footing-foundation wall joint, or up through floor cracks. It can cause major structural damage to foundation walls and is likely to contribute to mold, mildew, decay, and other moisture-related problems.

Dew Point

Temperature when water vapor in the air becomes saturated and condensation begins. Occurs when: 1. Moisture concentration increases 2. Air temperature decreases

vapor diffusion

slow movement of water molecules through vapor permeable materials

Capillary break

a gap or cavity in construction that discourages capillary action

Flashing Overlap

minimum 4" vertical overlap