Rainscreens, Barrier Walls and the Insulated Metal Panel ... Bar… · Rainscreens, Barrier Walls...

Rainscreens, Barrier Walls and the Insulated Metal

Panel Solution

© Metl-Span LLC, 2015

www.metlspan.com

http://www.metlspan.com/

Rainscreens, Barrier Walls and the Insulated Metal

Panel Solution

Metl-Span LLC

1720 Lakepointe Drive, Suite 101

Lewisville, TX 75057

Course Number: IMP003

Learning Units: 1 LU/HSW/SD Hour

Metl-Span LLC is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on

completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA

members are available upon request.

This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or

construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing,

or dealing in any material or product.

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without

written permission of the speaker is prohibited. .“LEED” and related logo is a trademark owned by the U.S. Green Building Council and is used by

permission.


Learning Objectives

At the end of this program, participants will be able to:

• identify various wall assemblies as rainscreens, mass walls and barrier walls

• understand the vapor and water management methods used by each type of wall assembly

• differentiate between vapor retarders and vapor barriers

• understand the difference between air/water barriers and vapor barriers

• utilize various rainscreen types with insulated metal panel barrier walls

• recognize and meet various code requirements using insulated metal panels - including air and

water infiltration and fire safety

I. Overview of IMPs as Rainscreen Barrier Walls Rainscreens = wall assemblies that consist of an exterior cladding, continuous air space with drainage plane and a barrier wall. Exterior cladding sheds most rain Air cavity/drainage plane allows drainage and evaporation Barrier wall provides backup water protection and primary air, thermal and moisture protection IMPs provide a state-of-the-art barrier wall for rainscreen applications. IMPs replace complicated multi-component assemblies used in traditional rainscreen designs (saves time and money).

Rainscreens, Barrier Walls and the IMP Solution

II. Water Management To understand rainscreens, mass/storage and barrier walls, let’s review the basic concepts of water infiltration… Water can penetrate a wall system by the following five (5) methods:

gravity kinetic energy (wind driven rain) surface tension (water clinging to itself) capillary action (water flow in narrow spaces, even uphill – think trees!) pressure differential (higher pressure on exterior vs. interior)


II. Water Management Now let’s look at how various wall types manage water infiltration…

“Perfect” barrier walls • metal panels (PEMB applications) • curtainwalls, storefronts

Mass/storage walls

• concrete tilt-up, concrete block, pre-cast

Rainscreen systems • drained and back vented

o brick veneer o metal panels o terra cotta o ACM/MCM (aluminum composite and metal composite panels)

• pressure equalized (allows walls to better resist wind driven rain)

Insulated metal panels


III. Wall Assemblies and Water Management “Perfect” Barrier Walls

weather protection by use of a single element examples:

• curtainwalls, storefront • metal siding on a pre-engineered metal building

may or may not contain separate vapor barriers success depends on quality of installation, longevity of gaskets and sealants cladding must resist all positive and negative wind loads

Advantages

• easy to inspect installation • repairs accessible from exterior of wall assembly • minimum components, straightforward installation

Disadvantages • seal failure leads to water intrusion – no backup system • seals degrade under normal exposure (UV, wind, rain) • failure may go undetected, resulting in damage (mold, mildew) • water enters building once past barrier wall


III. Wall Assemblies and Water Management “Perfect” Barrier Walls How metal siding resists water infiltration: Gravity - water travels down exterior panel surfaces

Kinetic energy - exterior surface sheds water, relies on lap sealants (if/when used)

Surface tension – flashings with drip edges

Capillary action – sealants between layered flashings

X Pressure differentials

no protection against pressure differences


III. Wall Assemblies and Water Management “Perfect” Barrier Walls (with secondary “gutter” backup)

barrier design, but with gutter system behind glazing/panels examples: curtainwalls, storefront windows glazing and spandrel panels must resist all negative and positive wind loads

Advantages

• minimum components, straightforward installation • relatively easy to inspect

Disadvantages • nowhere for water to go if it escapes gutter (mullion) system • minimum backup system (only at joints)


III. Wall Assemblies and Water Management Mass/Storage Walls How concrete tilt-up, concrete block and pre-cast walls resist water infiltration: Gravity – water drains down wall, some is absorbed due to porosity

walls dry out through evaporation and diffusion

Kinetic energy – water drains down wall surface, some water is absorbed (painting reduces absorption), gaps filled with sealant

Surface tension – reduced by water absorption

Capillary action – reduced by water absorption, sealant at transitions




Exposed sealant between panels

III. Wall Assemblies and Water Management Barrier walls with secondary “gutter” backup How curtainwall and storefront systems resist water infiltration: Gravity – water sheds down surface of glazing and within mullions.

Kinetic energy – glazing resists penetration, small amounts of water enter mullions, escapes through weep holes

Surface tension – gaskets surrounding glazing and spandrel panels

Capillary action – gaskets surrounding glazing and spandrel panels




III. Wall Assemblies and Water Management Rainscreen wall systems (two types): Drained and back ventilated Pressure equalized Both contain rainscreen (water shedding) component and backup barrier wall assembly

Advantages

• redundant system (outer rainscreen AND barrier wall) • does not rely on face seals • well understood technology • adaptive to many products (brick, tile, ceramic, glass, metal, ACM) • drainage cavity allows drainage and evaporation

Disadvantages

• multiple layers required • layers supplied and installed by different trades • interfaces between layers must be properly detailed and constructed • different regions of the country require different components and assemblies


III. Wall Assemblies and Water Management Rainscreen wall systems – drained and back ventilated

multiple component wall systems - each component performs a single function rainscreen element sheds majority of water – metal panels, ACM, brick, tile etc. barrier wall: residual water, air/vapor/thermal control 1”± gap between rainscreen and barrier wall creates air space, allows water to drain air space and venting allow convection and evaporation both rainscreen cladding and barrier assembly must resist positive and negative wind loads

Air/water/vapor and thermal control

Rainscreen element


III. Wall Assemblies and Water Management Rainscreen wall system components – drained and back ventilated

Interior gypsum Exterior gypsum Furring/hat channels/girts Tile support rails

Structural stud system Air/water barrier* Rigid insulation Rainscreen element


Barrier wall components and sequence may vary across climate zones

III. Wall Assemblies and Water Management How rainscreens (drained and back vented) resist water infiltration: Gravity

rainscreen deflects majority of water small amounts contact drainage plane, drains or evaporates

Kinetic energy

rainscreen deflects majority of water small amounts contact drainage plane, drains or evaporates

Surface tension - flashings with drip edges

Capillary action - sealants between layered flashings


Standard drained and back vented rainscreens do NOT protect against pressure differences


III. Wall Assemblies and Water Management Pressure Equalized Rainscreen Systems (PERS) Advantages:

most effective system for wind driven rain (high rises, coastal zones) pressure equalized wall system

Disadvantages:

extensive engineering analysis of wind loads compartment sizes, locations and vents engineered for every project detailed design of rainscreen/barrier wall interface requires high level of installation expertise

Rainscreens, Barrier Walls and the IMP Solution Compartment seals

Rainscreen

Air Barrier

Compartment seal

Drain vents

Flashing to outside

Barrier Wall

III. Wall Assemblies and Water Management Pressure Equalized Rainscreen Systems (PERS) wind loads are dynamic different pressures at corners, eaves, field zones, and within zones PERS compartmentalizes area behind panels compartments…

• sized according to project wind loads and building geometry • allows pressure equalization between rainscreen element and interior cavity • must be vented, equalization must occur within .08 seconds*

*requirement of AAMA 508 testing (Voluntary Test Method and Specification for Pressure Equalized Rainscreen Wall Cladding Systems)


Rainscreen

Air Barrier

Compartment seal

Drain vents

Flashing to outside

Barrier Wall

Pressure equalization requires backpressure!

III. Wall Assemblies and Water Management How rainscreens (PERS) resist water infiltration: Gravity

rainscreen deflects most water small amounts contact drainage plane, drains or evaporates

Kinetic energy

rainscreen deflects most water small amounts of water contact drainage plane, drains or evaporates



Pressure differentials

designed for pressure equalization back pressure forces water back out of wall assembly


Rainscreen

Air Barrier

Compartment seal

Drain vents

Flashing to outside

Barrier Wall

III. Wall Assemblies and Water Management How insulated metal panels resist water infiltration: Gravity

• water travels vertically down exterior panel surfaces • joint system, flashings direct water out of walls (exits at wall openings and at base)

Kinetic energy (wind driven rain)

• exterior panel surface sheds water • exterior joint keeps most water out • interior joint provides redundant air/water seal



Pressure differentials

• sealing interior joint allows pressure equalization within panel joint cavity


IV. Air and Vapor Management

Now, let’s take a look at the issues of air infiltration and vapor management… Concepts: Water vapor moves from high moisture to low moisture areas Warm air can hold more moisture than same amount of cold air Terms: Infiltration - air leakage into a building Exfiltration - air leakage out of a building Diffusion - the movement of vapor, even through air-tight assemblies Water barrier - physical barrier to passage of water (i.e. wall drainage plane) Air barrier - physical barrier to air infiltration (leakage) Vapor drive – direction of movement of water vapor through a wall or roof assembly. Can be in either direction (outside in or inside out).


IV. Air and Vapor Management Bulk water = liquid water (as opposed to water vapor or condensation) Vapor retarders = material used to slow the movement of vapor Vapor retarders come in three classifications: Class I: ≤ .1 perm (impermeable) Class II: > .1 perm ≤ 1.0 perm (semi-impermeable) Class III: > 1 perm ≤ 10 perm (semi-permeable) >10 perms = NOT a vapor retarder (considerable permeable) 1 perm = 1 grain of water vapor passing through 1 sf of an assembly per hour with ≈.5 psf pressure difference (1 grain ≈ 1 drop) Class I retarders are vapor barriers. IMPs because of their steel skins are considered vapor barriers.


Magnified view of building wrap vapor retarder – vapor passes through but not water

IV. Air and Vapor Management Vapor management (retarders and barriers) can be performed by any one of the following:

Latex paint or semi-permeable textured wall finish on interior gypsum Polyethylene sheathing behind interior gypsum wallboard Batt insulation with vinyl facing Air/water barriers Interior face of insulated metal panel (IMP)


Proper vapor barrier design depends on climate zone, building use and interior conditions.

IV. Air and Vapor Management Air/water barriers (AWBs) also known as WRBs (weather resistive barriers) Protect against air and water infiltration Allow movement of water vapor (prevents moisture buildup - walls can “breath”) Perm ratings vary greatly from product to product Can act as vapor retarders, but not barriers Two types: Fluid applied – brushed or sprayed on Building wraps – applied in the form of sheathing Examples: Blueskin® Tyvek® GreenGuard®


V. Rainscreens and the IMP Solution Let’s summarize what we’ve learned so far about rainscreen wall design: All rainscreens should be designed using these principles:

1. assume water and water vapor will penetrate the rainscreen and the barrier assembly 2. allow a means for water and water vapor to escape

Different rainscreen materials require different barrier wall assemblies to perform properly

Not all rainscreen wall assemblies are designed alike. Designs vary depending on moisture storage capacity of the

rainscreen (ex: brick vs. metal), climate zone, humidity and interior building use/environment. Multiple component barrier wall assemblies must be designed to allow moisture to diffuse out (to prevent, mold,

mildew and rust). Wall systems should NOT contain multiple vapor barriers.



V. Rainscreens and the IMP Solution

Product Configuration IMP facings: flat or lightly profiled with non-directional embossing Exterior gauge: minimum .016” G-90 (≥28 gauge) Interior gauge: 26, optional 24 or 22 Width: 42”

Lengths: 8’ to ≈ 24’ in 1/16” increments

Thicknesses: 2”, 3”, 4” Exterior paint finish is 1.0 mil. Polyester (White) Standard interior paint finish is 1.0 mil. Polyester (White)

R-values at 75⁰F mean temperature:

2” 3” 4”

15.14 22.27 29.42

V. Rainscreens and the IMP Solution Rainscreen and Horizontal Barrier Wall Combinations: 1. Horizontal barrier wall requires:

Stud wall construction (vertical) Horizontal IMP panels

2. Rainscreen panels Horizontal metal panels require vertical hat channels Vertical metal panels require horizontal hat channels (not shown) Tile/ceramic panels always require vertical tile rails ACM/MCM requires either vertical or horizontal hat channels (not shown) Brick uses brick ties through panels into studs (no hat channels)


V. Rainscreens and the IMP Solution Rainscreen and Vertical Barrier Wall Combinations: 1. Vertical barrier wall requires

Horizontal girts Vertical IMP panels

2. Rainscreen orientation Horizontal metal panels require vertical hat channels Vertical metal panels require horizontal hat channels (not shown) Tile/ceramic panels always require vertical tile rails ACM/MCM requires either vertical or horizontal hat channels (not shown) Brick uses brick ties through panels into studs (no hat channels)


© 2013 Panelmet Consulting, LLC


Interior gypsum Vapor retarder (optional) Stud wall Exterior gypsum Air/water barrier Furring/hat channels Rigid insulation Panel support hat channels Metal rainscreen panel

(8-9 components)


When this works better?

Interior gypsum Stud wall Insulated metal panels Hat channels Metal rainscreen panel

(5 components)

Metal Panel Rainscreen Assembly

Why do this?

Single component: Air barrier Vapor barrier Water barrier Thermal barrier


Insulated Steel Stud Wall with Masonry Veneer Interior gypsum Vapor retarder Infill metal studs Fiberglass batt cavity insulation Exterior grade gypsum Building wrap (Air space) Brick veneer rainscreen

(7 components)


When this works better?

IMP Barrier Wall with Masonry Veneer Interior gypsum Vapor retarder (optional) Infill metal studs Insulated metal panels (Air space) Brick veneer rainscreen

(4-5 components)

Brick Veneer Rainscreen Assembly

Why do this?

NOTE: Hat channels NOT used with brick veneer



Interior gypsum Vapor barrier (optional) Stud wall Exterior gypsum Air/water barrier Furring/hat channels Rigid insulation Tile support rails Terra cotta tile rainscreen

(8-9 components)


When this works better? Interior gypsum Stud wall Insulated metal panels Tile rails Terra cotta tile rainscreen

(5 components)

Terra Cotta Tile Rainscreen Assembly

Why do this?


V. Rainscreens and the IMP Solution Features and Benefits

Feature: Optional double joint sealed Benefit: Three lines of defense against water infiltration (outer rainscreen, exterior panel joint, interior panel joint).


V. Rainscreens and the IMP Solution Features and Benefits Feature: IMP barrier walls provide water barrier, insulation and air/vapor barrier Benefits: single source barrier wall, includes design, materials and pre-assembly simplified detailing and installation shortens construction time reduces number of trades and associated conflicts, simplifies liability issues less chance of catastrophic wall failure factory assembled, stringent quality control backed by physical testing Feature: Panels available up to 4” thick Benefits: high R values (up to R-29.42 @ 75⁰F), results in energy savings easy to predict dew point in wall assembly, greater control over vapor management Feature: Single step installation Benefit: Significant labor savings, especially projects with high labor rates (union labor, Davis Bacon Act)


V. Rainscreens and the IMP Solution Features and Benefits Feature: IMP panel facings are painted metal Benefits: protects insulation from moisture infiltration and outgassing (no loss of R value over time) resistant to physical damage – no punctures, tearing or delaminated seams Feature: Composite panel construction Benefits: capable of resisting live loads per code requirements for barrier walls exterior surface suitable for mounting rainscreen supports and hardware Feature: IMPs can withstand indefinite exposure to the elements during construction Benefit: more flexibility in shell completion schedule, allows interior work to progress Feature: IMPs barrier panels same as standard IMPs Benefit: Successful track record, millions of square feet installed as “perfect” barrier walls


VI. Frequently asked questions - General

Q1: What trades are involved in constructing a barrier wall using the IMP system? A1: IMP, architectural sheet metal or glazing contractors. Q2: Why does the IMP system work so well? A2: IMPs by themselves form an excellent barrier wall. Adding a rainscreen to IMPs provides maximum protection. Q3. Will the foam core of IMP panels soak up water and deteriorate? A3. No – the foam cores are 90%+ closed cell and designed for exterior applications. Q4: What air/water performance does the IMP system achieve? A4: Air infiltration test results (ASTM E283): .007 cfm @ 1.57 psf pressure differential (IBC code requirement: .04 cfm @ 1.57 psf pressure differential) Water infiltration test results (ASTM E331): 20 psf - no leakage (IBC code requirement: 6.24 psf – no leakage)


VI. Frequently asked questions - General Q5: Why the need for this product? Why cover up a perfectly good insulated metal panel? A5: Virtually unlimited design flexibility – accommodates nearly all rainscreen cladding types Easy to mix different rainscreens while maintaining uniform air/water/thermal protection Makes future retrofits of building exterior easy – does not require “opening up” walls to change appearance


VI. Frequently asked questions: APPLICATIONS

Q6: I want to add batt insulation in the stud cavity behind the IMP system. Because the interior side of the IMP panels acts as a vapor barrier, will this create condensation problems in the wall? A6: Design wall assembly so that the dew point occurs within the insulated metal panel layer (WUFI analysis) Rule of thumb ≈ 2/3 of wall R value should come from IMPs Do not use an additional vapor barrier Use proper HVAC design



VI. Frequently asked questions: FIRE SAFETY Q7: Can IMPs be used with all building classifications? A7: Yes if they comply with requirements outlined in Chapter 26 of the IBC (International Building Code).

Q8: Do IMPs carry an hourly fire-resistive rating? A8: IMPs may be used as a component of fire-rated wall construction; the actual rating is achieved by other materials

(such as concrete block or fire-rated gypsum board). Q9: Are IMP panels suitable for multi-story construction? A9: Yes in accordance with NFPA 285: Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of

Exterior Non-Load-Bearing Wall Assemblies Containing Combustible Components. Combustible rainscreens added to IMPs may require additional NFPA 285 testing.


VI. Frequently asked questions: FIRE SAFETY Q10: What other fire approvals/testing standards do IMPs carry? A10:

ASTM E84 – Surface burning characteristics NFPA 259 – Heat of Combustion NFPA 286 – Room Test UL 263 listing (U652 assembly) – IMP panels as component of 1 or 2 hour fire-rated wall construction Factory Mutual (FM 4880): Class 1 rating

(FM 4881): Class 1 Exterior Wall Systems

Thank you for your time

Questions?

This concludes the American Institute of

Architects Continuing Education Systems

Course

www.metlspan.com


http://www.website.com/

Rainscreens, Barrier Walls and the Insulated Metal Panel ... Bar… · Rainscreens, Barrier Walls...

Documents

Transcript of Rainscreens, Barrier Walls and the Insulated Metal Panel ... Bar… · Rainscreens, Barrier Walls...