WALL PERFORMANCE BY DESIGN: The Role of Rainscreens in Moisture
Management Laverne Dalgleish Building Enclosure Moisture Management
Institute (BEMMI) Slide 2 Todays Agenda BEMMI Background Exterior
Wall Science: As I Live and Breathe! Traditional Rainscreen Design
Engineered Rainscreen Design Absorptive Cladding Building Code
Requirements and Compliance Bibliography Slide 3 Building Enclosure
Moisture Management Institute Founded in 2009 Founding Members:
Advanced Building Products Benjamin Obdyke Cosella-Drken
CavClear/Archovations Slide 4 BEMMI Mission To promote the growth
of the engineered rainscreen products industry to improve moisture
management in building enclosures through technical advocacy Slide
5 Exterior Wall Science: As I Live and Breathe! Exterior Wall
Assembly Wall Covering Assembly Water-Resistive Barrier Insulating
Sheathing (continuous insulation) Structural Framing, Sheathing,
Cavity Insulation Interior Finish Materials Air Barrier
Requirements Penetrations Slide 6 Slide 7 Slide 8 Traditional
Rainscreen Design Ventilated Cladding Anchored Brick and Stone
Veneers Wood Shakes and Shingles Clapboards Drainage and Drying
Slide 9 Traditional Rainscreen Design Slide 10 Absorptive Cladding
Masonry and Stucco Adhered Veneers Wood Siding Materials
Engineered-wood Siding Materials Cement-based Siding Materials
Slide 11 Absorptive Claddings Slide 12 Engineered Rainscreen Design
Bulk Water Drainage Ventilation Precipitation, Condensation
Evaporation, Respiration Capillary Break Space Isolate Cladding
Slide 13 Engineered Rainscreen Design Types of Rainscreen Materials
3-dimensional membrane 3-dimensional mesh style Polymer-based
products Roll out similar to water-resistive barriers Continuous
airspace Slide 14 Engineered Rainscreen Design Slide 15 0.25 in
(6mm) 0.40 in (10mm) Meets Canadian Building Code Engineered
Rainscreen Design Slide 16 Slide 17 Slide 18 Code Requirements:
2012 IRC SECTION R703 EXTERIOR COVERING R703.1 General. Exterior
walls shall provide the building with a weather-resistant exterior
wall envelope. The exterior wall envelope shall include flashing as
described in Section R703.8. R703.1.1 Water resistance. The
exterior wall envelope shall be designed and constructed in a
manner that prevents the accumulation of water within the wall
assembly by providing a water-resistant barrier behind the exterior
veneer as required by Section R703.2 and a means of draining to the
exterior water that enters the assembly. Protection against
condensation in the exterior wall assembly shall be provided in
accordance with Section R702.7 of this code. Slide 19 Code
Requirements: 2012 IRC Exceptions: 1. A weather-resistant exterior
wall envelope shall not be required over concrete or masonry walls
designed in accordance with Chapter 6 and flashed according to
Section R703.7 or R703.8. Slide 20 Code Requirements: 2012 IRC
Exceptions (cont.): 2. Compliance with the requirements for a means
of drainage, and the requirements of Sections R703.2 and R703.8,
shall not be required for an exterior wall envelope that has been
demonstrated to resist wind-driven rain through testing of the
exterior wall envelope, including joints, penetrations and
intersections with dissimilar materials, in accordance with ASTM E
331 under the following conditions: Slide 21 Code Requirements:
2012 IRC 2.1. Exterior wall envelope test assemblies shall include
at least one opening, one control joint, one wall/eave interface
and one wall sill. All tested openings and penetrations shall be
representative of the intended end-use configuration. 2.2. Exterior
wall envelope test assemblies shall be at least 4 feet by 8 feet
(1219 mm by 2438 mm) in size. Slide 22 Code Requirements: 2012 IRC
2.3 Exterior wall assemblies shall be tested at a minimum
differential pressure of 6.24 pounds per square foot (299 Pa). 2.4.
Exterior wall envelope assemblies shall be subjected to the minimum
test exposure for a minimum of 2 hours. Slide 23 Code Requirements:
2012 IRC Pass / Fail Criteria Exception 2 (cont.): The exterior
wall envelope design shall be considered to resist wind-driven rain
where the results of testing indicate that water did not penetrate
control joints in the exterior wall envelope, joints at the
perimeter of openings penetration or intersections of terminations
with dissimilar materials. Slide 24 ASTM E331 Water penetration
test. Simulates 8 rain / hr. with 50 mph wind. Slide 25 Code
Requirements: 2012 IRC IRC Provides Basic Performance Measures
Minimum Code (minimum legal requirements) Beyond Code: Durability
Drainage and Drying Moisture Management as Preventative Measure
Slide 26 Performance Expectations Help Remove Bulk Water Promote
Drying of Incidental and Absorbed Water Improve Condensation
Management Slide 27 ICC-ES (Evaluation Services) Meeting the Intent
of the Code ICC-ES Acceptance Criteria: AC356 Drainage Test
Accelerated Aging & Weathering Durability / Fungi Resistance UV
Exposure Fire Resistance (optional) Slide 28 Blower-Door Testing
Slide 29 Problem Areas Tighter the wall, the less it dries
Penetrations and openings create moisture movement issues Less
expensive to address upfront than to fix later Slide 30 Engineered
Rainscreen Performance Drain bulk water from behind the cladding
Provide ventilation drying for other incidental moisture Separates
cladding from WRB Capillary break Surfactant issues, enhance WRB
durability Continuously over entire wall surface Slide 31
Engineered Rainscreen Details Rainscreen Material Slide 32 Review
BEMMI Background Exterior Wall Science: As I Live and Breathe!
Traditional Rainscreen Design Engineered Rainscreen Design
Absorptive Cladding Building Code Requirements and Compliance
Bibliography Slide 33 Questions? Slide 34 Bibliography Advanced
Building Productswww.mortairvent.comwww.mortairvent.com Air Barrier
Association of Americawww.airbarrier.orgwww.airbarrier.org
CavClear/Archovationswww.cavclear.comwww.cavclear.com Building
Enclosure Moisture Management Institutewww.bemmi.orgwww.bemmi.org
Benjamin Obdyke www.benjaminobdyke.comwww.benjaminobdyke.com
Cosella-Drkenwww.cosella-dorken.comwww.cosella-dorken.com
International Code Council, Evaluation
Serviceswww.icc-es.orgwww.icc-es.org International Code Council
www.iccsafe.orgwww.iccsafe.org Masonry Veneer Manufacturers
Associationwww.masonryveneer.orgwww.masonryveneer.org NAHB Research
Center White Paper
www.toolbase.org/PDF/DesignGuides/RainScreenDesigns.pdfwww.toolbase.org/PDF/DesignGuides/RainScreenDesigns.pdf
