1. The Ins and Outs of Metal Rainscreen Wall Systems
15 October 2012
SMACNA
69th Annual Convention
Las Vegas, Nevada
Presented by:
Jeff Ceruti

2. Outline Defining the Rainscreen Wall Metal materials Panel seam types
Pressure equalization
Water/Air barriers
Issues observed in practice – details, etc
Fire test requirements

3. What is a Rain Screen Wall?
Two fundamental approaches to design of exterior walls
Barrier Walls
Multi-wythe masonry
Early EIFS (no drainage)
Precast concrete
Insulated metal panels
Drainage Walls
Brick veneer
Rainscreen (metal, phenolic,stone, others)
Stucco
Vinyl/wood/cement siding
Drainable EIFS

4. What is a Rain Screen Wall?
Multi-wythe Masonry Barrier Wall
Relies on mass of masonry to absorb water and later evaporate; thick walls needed
Occasional leakage to interior during heavy storms

5. What is a Rain Screen Wall?
Surface Sealed Barrier Wall
Relies solely on the exterior surface of the wall to waterproof the building
Seal failures, breaches, discontinuities = leakage into building
No Redundancy

6. What is a Rain Screen Wall?
Drainage Walls
Cladding sheds bulk water down the façade
Allows some infiltration
Drainage cavity or media allows infiltration to drain down
Water-resistant barrier behind the cladding
Prevents water from entering building
Flashings at intervals drain any infiltration to the exterior
Openings for drainage also allow venting (drying) of cavity
Two basic types:
No or minimal cavity (clapboards, siding, stucco over water barrier)
Wide cavity (brick veneer, metal panels, dimensional stone, clay tile, phenolic panels, etc.)

7. What is a Rain Screen Wall?
Drainage Walls
Cladding is not air or water tight
Some test data for water penetration relies on back-up wall – not a true measure of the cladding system
Thermal insulation
Cladding
Water-resistant barrier
Drainage space/plane
Flashing

8. What is a Rain Screen Wall?
Back-up Wall
Critical for overall wall performance
Water barrier
Air barrier
Thermal insulation
Vapor retarder
Exterior covering is primarily for aesthetics
Thermal insulation
Cladding
Water-resistant barrier
Drainage space/plane
Flashing

9. Metal Panel Rainscreen Materials
Aluminum Composite Material (ACM)
Thin aluminum sheet with core material; total 4 mm (5/32 in.)
Polyethylene – height limit to 40 ft for non-combustible construction
Fire retardant (proprietary)
Honeyconmb (limited manufacturers)
Various finishes – painted, metallic, anodized, natural

10. Metal Panel Rainscreen Materials
Aluminum plate
Not widely used
Returns are bent; not as square as ACM
Copper sheet/plate
Durable
Natural weathering
Potential staining issue
Green sidewalks

11. Metal Panel Rainscreen Materials
Zinc Composite Material
Same construction as aluminum, with zinc both sides
Greater thermal movement
Significant concern of accelerated corrosion on back-side
Must be vented to dry back side of panels

12. Metal Panel Rainscreen Materials
Zinc Composite Material
Same construction as aluminum, with zinc both sides
Greater thermal movement
Significant concern of accelerated corrosion on back-side
Stainless steel plate
Variety of finishes available, stainless steel types
Titanium
Very expensive
Difficulty in matching finish
Others…

13. Metal Panel Rainscreen Materials
Aluminum Composite Material (ACM)
Long term track record

14. Metal Panel Rainscreen Materials
Aluminum Composite Material (ACM)
Flexibility in design

15. Metal Panel Rainscreen Materials
Aluminum Composite Material (ACM)
Flexibility in design

16. Metal Panel Rainscreen Materials
Aluminum Composite Material (ACM)
Flexibility in design

17. Metal Panel Rainscreen Materials
Aluminum Composite Material (ACM)
Flexibility in design

18. Metal Panel Rainscreen Materials
Aluminum Composite Material (ACM)
Flexibility in design

19. Metal Panel Rainscreen Materials
Aluminum Composite Material (ACM)
Flexibility in design

20. Metal Panel Rainscreens
Aluminum Composite Material
Route back side to form bends

21. Metal Panel Rainscreens
Aluminum Composite Material
Route back side to form bends

22. Metal Panel Rainscreen
Aluminum Composite Material
Route back side to form bends

23. Procurement methods Pre-manufactured Shop manufactured
Purchase formed panels, sub-girts, etc. from manufacturer
Fittings, clips, gaskets, anchors
Testing provided (structural, fire, etc.)
Structural design calculations (panels, sub-girts, attachments)
Track record for system
Shop manufactured
Purchase panel materials, sub-girts members, fittings, gaskets, etc.
Determine panel design, pieces used, drainage considerations
Testing of “system”
Structural design calculations
Track record?

24. Panel Joint Types Wet-sealed Joints
Rout and return, with exposed sealant joint
Sealant is labor intensive
Joint failures inevitable
Thermal movement
Weathering
Joint geometry
Workmanship
Maintenance issue for owner
Increase reliance on back-up barriers
Replacing sealant without damaging finish
Full seals create vapor retarder

25. Panel Joint Types Gasketed Joints Various designs Not a complete seal
Concealed gaskets; some with raised stems
Exposed push-in gaskets
Not a complete seal
Openings at joints, corners
Exposed gaskets prone to loosening, can fall out with thermal movement
Less maintenance than sealed joints
Some sequential installation, some not
Affects panel removal

26. Panel Joint Types Gasketed Joints Various designs Not a complete seal
Concealed gaskets; some with raised stems
Exposed push-in gaskets
Not a complete seal
Openings at joints, corners
Exposed gaskets prone to loosening, can fall out with thermal movement
Less maintenance than sealed joints
Some sequential installation, some not
Affects panel removal
Gutter

27. Panel Joint Types Overlap systems
Panels “shingled” similar to traditional cladding
Sequential installation
Difficult to remove panel in middle of wall
Internal guttering and drainage common
No maintenance involved
Typically good water management

28. Panel Joint Types Spline systems
ACM used as backing spline behind joint
Varying design
Some resist water better than others
Depends on internal guttering
Sequential installation
No maintenance involved

29. Panel Joint Types Spline systems
ACM used as backing spline behind joint
Varying design
Some resist water better than others
Depends on internal guttering
Sequential installation
No maintenance involved

30. Panel Joint Types Spline systems
ACM used as backing spline behind joint
Varying design
Some resist water better than others
Depends on internal guttering
Sequential installation
No maintenance involved
Double spline systems
Improved performance
Pressure equalized

31. Pressure-equalized Systems
Function differently than Rainscreens
Positive wind pressure drives water against wall
Air fills cavity, equalizing pressure
Lack of pressure difference reduces infiltration
No driving force
Incidental water drained at intervals
Thermal insulation P+
Cladding P+
Weather-resistant barrier
Drainage/ventilation space/plane
Flashing

32. Pressure-equalized Systems
Intricate design
Cavity must be compartmentalized to control pressure (airtight)
Fine tuning between compartment size and vent size
Sizing different for each building; sometimes for areas of same building (corners)
Testing per AAMA 508
Thermal insulation
Cladding
Weather-resistant barrier
Drainage/ventilation space/plane
Flashing P+

33. Pressure-equalized Systems
Does it work?
Lab tests can show the pressure equalization
Can be difficult to achieve in the field
Pre-manufactured systems can perform
Field-built systems more difficult
Difficult to measure effectiveness in the field
Variable wind pressures

34. Pressure-equalized Systems
Does it work?
Lab tests can show the pressure equalization
Can be difficult to achieve in the field
Pre-manufactured systems can perform
Field-built systems more difficult
Difficult to measure effectiveness in the field
Variable wind pressures

35. Pressure-equalized Systems
Is it needed?
Originated when felt paper used on the back-up wall
Improved air/water barrier materials
Improved detailing (air barriers; flashing)
More attention to installation of barriers

36. Air/Water Barriers
Most critical component of wall design

37. Air/Water Barriers Most critical component of wall design Functions
Keeps water out of building
Last line of defense
Keeps building airtight
Condensation, energy
Might be vapor retarder

38. Air/Water Barriers Most critical component of wall design Functions
Keeps water out of building
Last line of defense
Keeps building airtight
Condensation, energy
Might be vapor retarder
Must be integrated with surrounding components
Wall attachments
Windows
Penetrations
Roof

39. Air/Water Barriers Materials: Rubberized asphalt sheet
Primary material – highly reliable
Provides vapor retarder

40. Air/Water Barriers Materials: Rubberized asphalt sheet
Primary material – highly reliable
Provides vapor retarder
Vapor permeable sheets
Adhered
Short track record – only a few years on market
Some adhesion issues
Primers may not be permeable

41. Air/Water Barriers Materials: Rubberized asphalt sheet
Primary material – highly reliable
Provides vapor retarder
Vapor permeable sheets
Adhered
Short track record – only a few years on market
Some adhesion issues
Primers may not be permeable
Polyolefin sheets
Not adhered; vapor permeable
Successful if properly installed
Often see installation issues

42. Air/Water Barriers
Materials:
Liquid Applied
Short track record

43. Air/Water Barriers Materials: Liquid Applied Short track record
Have seen issues with many products

44. Air/Water Barriers Materials: Liquid Applied Short track record
Have seen issues with many products
Sheathing Joints
Fasteners
Cracking/crazing
Washing off wall

45. Air/Water Barriers Materials: Liquid Applied Short track record
Have seen issues with many products
Sheathing Joints
Fasteners
Cracking/crazing
Washing off wall

46. Air/Water Barriers Materials: Liquid Applied Short track record
Have seen issues with many products
Sheathing Joints
Fasteners
Cracking/crazing
Washing off wall
SGH testing shows:
Some with high absorption
Some with high filler content
Some are water soluble
No standards for durability
Prefer sheet membranes until these issues are resolved

47. Back-up Framing Galvanized steel (G90) is most common
Open joint systems (terra cotta, Trespa) use stainless or aluminum

48. Back-up Framing Galvanized steel (G90) is most common
Open joint systems (terra cotta, Trespa) use stainless or aluminum
Compatibility issue between aluminum and galvanized
Aluminum will accelerate zinc corrosion
Should consider upgrading for any open joint system
What about sealed systems?
Owner maintenance issue

49. Window Details Flashing
Sill flashing critical to prevent against leakage through window
Long-term concern
Break down of window seals
Integrate sill flashing with Air/Water barrier
Water barrier continuity
Air barrier continuity
Install panels without compromising barriers

50. Window Details Metal panel detailing can be complicated
Barrier/flashing continuity
Sequencing of installation
Panel attachment

51. Window Details Metal panel detailing can be complicated
Barrier/flashing continuity
Sequencing of installation
Panel attachment
Avoid fasteners through sill flashing

52. Window Details Metal panel detailing can be complicated
Barrier/flashing continuity
Sequencing of installation
Panel attachment
Avoid fasteners through sill flashing
Intermittent clips for connecting panels
Requires some exposed fasteners

53. Window Details Metal panel detailing can be complicated
Barrier/flashing continuity
Sequencing of installation
Panel attachment
Avoid fasteners through sill flashing
Anchor outboard of flashing

54. Window Details Head conditions: Avoid draining water into window head
Barrier continuity
Sequencing of installation
Panel attachment

55. Window Details Head conditions: Avoid draining water into window head
Barrier continuity
Sequencing of installation
Panel attachment

56. Window Details Head conditions: Flanged windows
Avoid draining water into window head
Barrier continuity
Sequencing of installation
Panel attachment
Flanged windows
Integral metal flange on aluminum windows
Connect AWB to flange

57. Window Details Head conditions: Flanged windows
Avoid draining water into window head
Barrier continuity
Sequencing of installation
Panel attachment
Flanged windows
Integral metal flange on aluminum windows
Connect AWB to flange

58. Window Details Jamb conditions: Flanged windows Barrier continuity
Sequencing of installation
Panel attachment
Flanged windows
Integral metal flange on aluminum windows
Connect AWB to flange

59. Window Details Flanged windows
Sill conditions - still provide pan flashing beneath window
Cut flange at sills – flange prevents window leakage from draining into cavity

60. Curtain Wall Details

61. Curtain Wall Details
Transition Water/Air Barrier into Glazing Pocket

62. Other conditions

63. Other conditions Horizontal flashing between windows
Drain water out of cavity at intermittent levels

64. Other conditions Horizontal flashing between windows
Drain water out of cavity at intermittent levels

65. Other conditions Upward facing surfaces (i.e., “roofs”)
Panel intended to shed water on vertical surfaces
Not intended for low-sloped surfaces
Expect leakage through joints
Requires membrane roofing below
“Gutter” detail at joints to control leakage through anchors
Better to detail using metal coping with watertight joints

66. Code Requirements – fire protection
International Building Code (2009)
Permits combustible materials in non-combustible construction
Combustible materials required to be tested, including:
Exterior Insulation and Finish Systems (EIFS)
Metal Composite Materials (MCM)
Fiber Reinforced Polymers
Foam Plastic Insulation
2012 IBC includes:
High-Pressure Laminates (HPL)
Water-resistive Barrier Materials
Certain exceptions based on building height, sprinklered building, etc.

67. Code Requirements – fire protection
International Building Code (2009)
Permits combustible materials in non-combustible construction
Combustible materials required to be tested, including:
Exterior Insulation and Finish Systems (EIFS)
Metal Composite Materials (MCM)
Fiber Reinforced Polymers
Foam Plastic Insulation
2012 IBC includes:
High-Pressure Laminates (HPL)
Water-resistive Barrier Materials
Certain exceptions based on building height, sprinklered building, etc.

68. The NFPA 285 Fire Test 11 September 2012
NFPA 285 Fire Testing for Exterior Walls
11 September 2012

69. The NFPA 285 Fire Test 11 September 2012
NFPA 285 Fire Testing for Exterior Walls
11 September 2012

70. The NFPA 285 Fire Test 11 September 2012
NFPA 285 Fire Testing for Exterior Walls
11 September 2012

71. The NFPA 285 Fire Test Most MCM panels can pass test
Typically tested without foam insulation
Test may not be valid depending on wall assembly make-up
NFPA 285 Fire Testing for Exterior Walls
11 September 2012

72. The NFPA 285 Fire Test
Limited database of tests available with actual assemblies used
Tests performed by manufacturers
Insulation
Metal Panels
Water-resistive barrier
Not coordinated amongst manufacturers
May limit certain combination of manufacturers
Some now coordinating – which does limit manufacturers
Trespa wall panels and Vaproshield WRB
NFPA 285 Fire Testing for Exterior Walls
11 September 2012

73. The NFPA 285 Fire Test Engineering judgments
Currently being used for WRB products, with small scale fire testing
Could be used for substituting manufacturers within assembly
Most manufacturers aware of requirements
Designers and Code officials becoming increasing aware of the requirements
NFPA 285 Fire Testing for Exterior Walls
11 September 2012

74. Jeff Ceruti, P.E. jjceruti@sgh.com 781-907-9214
Questions?
Jeff Ceruti, P.E.