1. Building Enclosure Moisture Management Institute (BEMMI)
WALL PERFORMANCE BY DESIGN: The Role of Rainscreens in Moisture Management
Laverne Dalgleish
Building Enclosure Moisture Management Institute (BEMMI)

2. Today’s 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

3. Building Enclosure Moisture Management Institute
Founded in 2009
Founding Members:
Advanced Building Products
Benjamin Obdyke
Cosella-Dörken
CavClear/Archovations

4. BEMMI Mission
To promote the growth of the engineered rainscreen products industry to improve moisture management in building enclosures through technical advocacy

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

8. Traditional Rainscreen Design
Ventilated Cladding
Anchored Brick and Stone Veneers
Wood Shakes and Shingles
Clapboards
Drainage and Drying

9. Traditional Rainscreen Design

10. Absorptive Cladding Masonry and Stucco Adhered Veneers
Wood Siding Materials
Engineered-wood Siding Materials
Cement-based Siding Materials

11. Absorptive Claddings

12. Engineered Rainscreen Design
Bulk Water Drainage
Ventilation –
Precipitation, Condensation
Evaporation, Respiration
Capillary Break Space – Isolate Cladding

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

14. Engineered Rainscreen Design

15. Engineered Rainscreen Design Meets Canadian Building Code
0.25 in (6mm)
0.40 in (10mm)
Meets Canadian Building Code

16. Engineered Rainscreen Design

17. Engineered Rainscreen Design

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 R R 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.

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.

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:

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 Exterior wall envelope test assemblies shall be at least 4 feet by 8 feet (1219 mm by 2438 mm) in size.

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) Exterior wall envelope assemblies shall be subjected to the minimum test exposure for a minimum of 2 hours.

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.

24. ASTM E331 Water penetration test.
Simulates 8” rain / hr. with 50 mph wind.

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

26. Performance Expectations
Help Remove Bulk Water
Promote Drying of Incidental and Absorbed Water
Improve Condensation Management

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)

28. Blower-Door Testing

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

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

31. Engineered Rainscreen Details
Rainscreen Material

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

33. Questions?

34. Bibliography
Advanced Building Products Air Barrier Association of America CavClear/Archovations Building Enclosure Moisture Management Institute Benjamin Obdyke Cosella-Dörken International Code Council, Evaluation Services International Code Council Masonry Veneer Manufacturers Association NAHB Research Center White Paper