Laverne Dalgleish Building Enclosure Moisture Management Institute BEMMI Todays Agenda BEMMI Background Exterior Wall Science As I Live and Breathe Traditional Rainscreen Design Engineered ID: 566561
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WALL PERFORMANCE BY DESIGN: The Role of Rainscreens in Moisture Management
Laverne Dalgleish
Building
Enclosure Moisture Management Institute (BEMMI)Slide2
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
BibliographySlide3
Building Enclosure Moisture Management Institute
Founded in 2009
Founding Members:
Advanced Building Products
Benjamin
Obdyke
Cosella-Dörken
CavClear/
ArchovationsSlide4
BEMMI Mission
To promote the growth of the engineered
rainscreen
products industry to improve moisture management in building enclosures through technical advocacySlide5
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
PenetrationsSlide6Slide7Slide8
Traditional Rainscreen Design
Ventilated Cladding
Anchored Brick and Stone Veneers
Wood Shakes and Shingles
Clapboards
Drainage
and
DryingSlide9
Traditional Rainscreen DesignSlide10
Absorptive Cladding
Masonry and Stucco
Adhered Veneers
Wood Siding Materials
Engineered-wood Siding Materials
Cement-based Siding MaterialsSlide11
Absorptive CladdingsSlide12
Engineered Rainscreen Design
Bulk Water Drainage
Ventilation –
Precipitation, Condensation
E
vaporation, Respiration
Capillary Break Space – Isolate CladdingSlide13
Engineered Rainscreen Design
Types of Rainscreen Materials
3-dimensional membrane
3-dimensional
m
esh
s
tyle
Polymer-based productsRoll out similar to water-resistive barriersContinuous airspaceSlide14
Engineered
Rainscreen
DesignSlide15
0.25 in (6mm)
0.40 in (10mm)
Meets Canadian Building Code
Engineered
Rainscreen
DesignSlide16
Engineered Rainscreen DesignSlide17
Engineered Rainscreen DesignSlide18
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.Slide19
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.Slide20
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:Slide21
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.Slide22
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.Slide23
Code Requirements: 2012 IRCPass / 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.Slide24
ASTM E331
Water penetration test.
Simulates 8” rain / hr. with 50 mph wind. Slide25
Code Requirements: 2012 IRC
IRC Provides Basic
P
erformance Measures
Minimum Code (minimum legal requirements)
Beyond Code:
Durability
Drainage and Drying
Moisture Management as Preventative Measure Slide26
Performance Expectations
Help Remove Bulk Water
Promote Drying of Incidental and Absorbed Water
Improve Condensation ManagementSlide27
ICC-ES (Evaluation Services)
Meeting the
I
ntent of the
C
ode
ICC-ES Acceptance Criteria: AC356
Drainage TestAccelerated Aging & Weathering
Durability / Fungi ResistanceUV ExposureFire Resistance (optional)Slide28
Blower-Door TestingSlide29
Problem Areas
Tighter the wall, the less it dries
Penetrations and openings create moisture movement issues
Less expensive to address upfront than to fix laterSlide30
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
C
ontinuously over entire wall surfaceSlide31
Engineered Rainscreen Details
Rainscreen MaterialSlide32
Review
BEMMI Background
Exterior Wall Science: As I Live and Breathe!
Traditional
Rainscreen
Design
Engineered
Rainscreen
DesignAbsorptive CladdingBuilding Code Requirements and ComplianceBibliographySlide33
Questions?Slide34
Bibliography
Advanced
Building Products
www.mortairvent.com
Air Barrier Association of America
www.airbarrier.org
CavClear/
Archovations www.cavclear.com Building Enclosure Moisture Management Institute www.bemmi.org
Benjamin Obdyke www.benjaminobdyke.comCosella-Dörken www.cosella-dorken.comInternational Code Council, Evaluation Services
www.icc-es.orgInternational Code Council www.iccsafe.orgMasonry Veneer Manufacturers Association www.masonryveneer.org NAHB Research Center White Paper
www.toolbase.org/PDF/DesignGuides/RainScreenDesigns.pdf