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Kingspan Insulation LLC2100 River Edge Parkway, Suite 175

Atlanta, GA 30328 Tel: 800-241-4402Fax:678-589-7320

Web: www.kingspaninsulation.us

©2006, 2016 Kingspan Insulation LLC. The material contained in this course was researched, assembled, and produced by Kingspan Insulation LLC and remains their property. Questions or concerns about the content of this course should be directed to the program instructor. This multimedia product is the copyright of AEC Daily.

Moisture Management in Walls

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©2006, 2016 Slide 2 of 62

Moisture Management in Walls

Presented By: Kingspan Insulation LLC2100 River Edge Parkway, Suite 175Atlanta, GA 30328

Description: Provides an overview of preventing and managing moisture in walls.

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The American Institute of Architects · Course No. AEC117 · This program qualifies for 1.0 LU/HSW Hour.

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AEC Daily Corporation has met the standards and requirements of

the Registered Continuing Education Program. Credit earned on

completion of this program will be reported to RCEP at RCEP.net.

A certificate of completion will be issued to each participant. As

such, it does not include content that may be deemed or construed

to be an approval or endorsement by the RCEP.





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Purpose and Learning Objectives

Purpose: Provides an overview of preventing and managing moisture in walls.

Learning Objectives:

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

• discuss where moisture in walls comes from and the problems it can cause

• explain the key design strategies and considerations to prevent moisture problems

• define the products that help manage moisture in a wall and how to install them correctly, and

• summarize the wall assembly drainage details for different wall types.





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How to Use This Online Learning Course

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An Introduction to Moisture Management





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Why Moisture Management is Important

Protecting a building from moisture damage isjust as important as protecting it from fire and structural failure. However moisture damage often happens undetected, which allows it to continue until serious problems occur.

Moisture can degrade a building’s envelope and structure, leading to a variety of problemsfrom less severe appearance issues, like efflorescence and spalling, to serious problems like structural failure and mold growth. Moisture can also reduce the effectiveness of thermal insulation.

The durability of a home is affected by how well it is protected from moisture. Homes that manage moisture properly will last much longer.





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Signs of Moisture Damage

Moisture damage usually happens within the wall making it invisible. However, some signs to look for include:

• Dampness, wet patches or condensation

• Odors

• Discoloration

• Peeling paint

• Mold or mildew





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Why There Are So Many Moisture Problems Today

There is an increasing number of moisture problems today because as homes become more energy efficient they also become more airtight. These “sealed” homes don’t breathe as much as older homes. If they aren’t designed and constructed correctly, they create the perfect environment for moisture problems.

Another cause of moisture problems today is the incorrect use and installation of moisture managing products. Even the best product will not work if it is installed incorrectly.





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Where Moisture in Walls Comes From

Moisture can come from two sources. It either leaks into the wall as a liquid from the outside, usually due to precipitation, or it enters as vapor from either the exterior or the interior. Vapor in the interior is generated everyday by activities like cooking and showering.

Another source of moisture in walls is called construction moisture. This is the water that is contained within the building materials when the wall is constructed. It is therefore important to ensure that materials will be able to dry adequately after construction.





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The Building Working as a System

While this presentation is primarily focused on managing liquid moisture, one needs to be informed on the building working as a system.

All of the following items need to be addressed:• Control water infiltration as your first line of defense• Control air flow to prevent moisture traveling on air currents• Permit drying of the structure• Be cognizant of the indoor air quality





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Preventing Moisture Problems





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The 4 D’s

There are four design strategies that can be applied to manage moisture in walls called the 4 D’s. They are deflection, drainage, dryingand durability. These strategies can be applied at the level of building design and at the level of the detail.

The key to moisture management is to first prevent moisture from getting into the wall (deflection). Then any moisture that does get into the wall needs to be managed (drainage, drying and durability) so that it gets out as quickly as possible.

Every moisture management strategy should have several “lines of defense”, because moisture will always find a way of getting in.





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Deflection

Deflection is the first moisture management strategy since it prevents moisture from penetrating the wall in the first place.

The intent of this principal is to “deflect” water away from the wall. Deflection strategies include roof overhangs, gutters, projecting sills, wall claddings and deflecting details like drip edges, flashing and sealant.

Wall assemblies with air spaces behind the cladding are also a method of deflection.





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Drainage

After deflection, drainage is the next line of defense against moisture. At the level of building design, drainage prevents water from standing by moving it away using sloped roofs and surfaces.

At the level of the wall assembly, drainage strategies incorporate details that move moisture out of the wall. Most commonly this is a drainage plane between the wall cladding and the sheathing, and flashing around windows and doors.





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Drying

Drying is the mechanism by which moisture accumulations are removed from the wall. Wall assemblies must be designed to allow sufficient drying of both the cladding and the sheathing.

The drying potential of the wall is affected by several factors including vapor and moisture barriers, the permeability of the cladding, and even the interior finish materials.

Cavities created behind the cladding for drainage also allow air flow which improves the drying capacity of the assembly.





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Durability

Durability refers to the moisture tolerance of the materials in the wall assembly. Durable materials should be selected to avoid moisture problems in cases when deflection, drainage and drying have not been able to remove all moisture. This is especially important for areas with high levels of moisture in the air and/or precipitation.





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Moisture Management Products





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Building Wrap: Introduction

Building wrap is one of the most important elements in a wall system. It is a continuous moisture resistant barrier that is wrapped around the exterior of a house between the cladding and the sheathing.

It acts as a barrier to air infiltration, which improves the wall’s resistance to heat loss. However, it still allows vapor to pass through from either side. This breathing prevents moisture from getting trapped in the walls.

It also acts as a moisture barrier and drainage plane, preventing liquid infiltration from the exterior. It acts as a second line of defense should any moisture get through the cladding.





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Building Wrap Types

There are three main types of building wrap: perforated, non-perforated and channeled. Perforated and non-perforated building wraps describe the means by which breathability, or permeance is achieved. Perforated wraps have micro-perforations to allow moisture vapor to pass through the film. Non-perforated wraps achieve breathability through the structure of the fabric or film. Channeled building wrap has drainage channels integrated into it that help move water out of the wall.

An important characteristic of building wrap is the perm rating. This is a measure of how breathable it is. The building code mandates that a building wrap have a perm rating above 5. This will provide adequate transmission to allow vapor to pass through. Keep in mind that overall wall breathability is determined by the perm rating of all the wall components. For example, OSB sheathing has a perm rating of less than one. Therefore the overall breathability of the wall system may be limited by any one component.

Other characteristics to look for in building wrap include strength, tear-resistance and UV stability. Building wraps should be tear resistant so that they are not damaged during the installation process. Damaged building wrap will not perform properly and will have to be repaired. UV stability provides a window of time between the installation of the building wrap and the installation of the cladding, where the building wrap will not degrade due to exposure to sunlight.





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Building Wrap: Installation

If building wrap is not installed properly it will not function effectively and can even be detrimental. Building wrap must always be installed so that it channels water out of the wall system and so that water is never allowed to flow inside of the wrap.

Building wrap can be installed over structural sheathing board, insulation board and sometimes framing members. It should be fastened securely to the structural sheathing, through insulation board to a framing member, or directly to a stud. It should be installed before windows and doors.

Fasteners should be spaced every twelve-sixteen inches along every other stud. Common galvanized roofing nails, plastic cap nails or staples with a minimum one-inch crown can be used.

Horizontal seams must be overlapped a minimum of two inches. Vertical seams must be overlapped a minimum of six inches. All seams can be taped to increase the efficiency of the system. Upper courses of building wrap must overlap lower courses (so water will be shed.)





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Seam Tape

Seam tape enhances the effectiveness of other products. It is used to seal joints and seams on building wraps and sheathings, adding extra protection against air and moisture penetration. It is also used at window and door openings to seal joints.

Seam tape can be used to repair rips and tears in damaged building wrap.

It should always be applied to a clean, dry, dust-free surface. Application can be done by hand or using a taping device.





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Flashing: Introduction

Flashing is a strip of impervious material that helps drain water to outside the wall, preventing it from getting trapped inside the wall.

It is used at roof valleys and intersections (with chimneys, walls, dormers), window and door openings, and other wall or roof openings or penetrations (such as for a vent pipe, at sill plates, etc.).





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Flashing Types

There are three main types of flashing: sheet metal, composite and plastic/rubber.

Stainless steel and copper flashing is very durable but expensive. This type of flashing has to be bent into shape which can be a labor intensive process.

Composite flashing combines thin metal sheets with a flexible compound coating. This makes them easier to bend into shape. There are some durability concerns with this type of flashing.

Plastic and rubber flashings are very popular because they are economical and easy to work with. They are flexible and easy to form into any shape. Many plastic/rubber flashings are self-adhering which makes installation quick and easy.

No matter the type, all flashing should be impervious to water, resistant to puncture and tears, UV resistant, and corrosion resistant. The flashing’s compatibility with adjoining materials and joint sealant should also be checked. It is quite difficult to replace flashing so durability is essential.





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Installation at Windows

This typical “best practice” method of installation for new construction is based on ASTM E 2112 Method A1.

• Once the building wrap has been installed over the entire exterior wall, make a modified “I” cut through the building wrap at the window opening (see diagram). Fold excess material inside the rough opening and fasten securely through all layers to a framing member.

• Cut a header flap in the building wrap at the top of the window. Temporarily tape the top edge of this flap up.

Building Wrap





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Install the horizontal sill flashing material next. The sill flashing should always be long enough to extend beyond the jamb flashing.

Sill Flashing Option 1:

• Install sill flashing that is at least twelve inches longer than the width of the rough opening.

• Align flashing so that it extends at least two inches onto the sill and up inside the jamb.





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• Install a sloped sill directly over the building wrap at the sill.

• Then install flashing over-top as described in Option 1.





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• Install a sill dam directly over the building wrap at the back of the sill.

• Then install flashing over-top as described in Option 1.





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• Install a sill pan directly over the pre-flashed sill after applying a bead of sealant to the backside of the front edge of the sill pan (see diagram).

• Attach the sill pan using roofing nails or panhead screws as shown.

• Then install small pieces of flashing at the sill corners so that they overlap the sill pan edges and the side jamb





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Window installation:

Install the window in accordance with the manufacturer’s installation requirements.

• Typically a bead of sealant is applied to the back side of the window flange prior to installation.

• It is important that the bottom flange of the window is not sealed.

• The window should then be attached as recommended by the manufacturer.





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Jamb Flashing:

• Install jamb flashing so it extends at least eight and a half inches beyond the rough opening sill and head.

• The jamb flashing should overlap the sill flashing.

Building Wrap





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Head Flashing:

• Install head flashing so it extends beyond the jamb flashing.

• Fold the building wrap down at the header so that it overlaps the head flashing. Tape over the entire diagonal cuts made in the building wrap at the header.

Please remember the exam password FLASHING. You will be required to enter it in order to proceed with the online examination.





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Installation at Windows Example

Example of well installed flashing:





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Installation at Arched Window

Flexible flashing will conform to the contour of any opening with arched or curved shapes. Arched openings are flashed in the same sequence as regular openings. It is important that all flashing seams be overlapped at least six inches.

Building Wrap





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Installation at Ledger Board

Flashing should be installed at areas where there is an attachment made to an exterior wall, such as the attachment of a deck or porch. This diagram shows how flashing should be installed at the ledger board of a deck attachment.

Building Wrap





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Installation at Sill Plate

Flashing should be installed at all sill plate locations, between the sill plate and the foundation and over the seam, between the sill plate and the foundation wall.

Building Wrap





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Installation at Wall/Roof Intersections

Areas where a roof meets a wall (or in areas where one roof intersects another roof) should be flashed.

Building Wrap





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Installation at Wall Penetrations

When penetrations, such as those for pipes and ducts, breach the building wrap, they must be sealed to the building wrap using a sealant that is compatible with both the building wrap and the pipe or duct material. Flexible flashing is ideal in this situation.

Unfold flashing against building wrap





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Typical Commercial Construction Details





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Through Wall Flashing Detail





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Shelf Angle Detail – Note Underside





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Cantilever Detail – Note Underside





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2 Options for Concrete Columns





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Parapet Walls

Building Wrap

Flashing





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Typical Commercial Construction Window Flashing

Non-Flanged Window





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Trim sides and bottom flush with edge – prep angle cut for head





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Tape sides and head to hold down wrap





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Install sill flashing





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Finish sill flashing and install side flashing





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Prime sheathing on head





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Install head flashing





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Finish head flashing and seal exterior and interior

Interior





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XPS Wall Sheathing

Extruded polystyrene (XPS) board acts as a wall sheathing in place of the traditionally used plywood sheathing.

The main difference with XPS board is its insulating properties. It provides four times the R-value of wood sheathing. It is also lightweight and easy to install.

XPS board also acts like a building wrap and drainage plane, resisting liquid moisture while allowing trapped vapor to escape.





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Directing Water from The Roof

Roof drainage and water-tightness are also important considerations to ensure a long life for any home.

Roof design and shape should be used to direct water away from walls. Overhangs can prevent precipitation from coming in contact with walls. Roofs should never deposit water onto a wall as this can lead to severe moisture problems.

It is important that roofs have properly installed water proofing membranes, flashing and drip edges to manage moisture and protect the building.

Building Wrap





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Directing Water from The Foundation

It is also critical to protect the foundation walls from moisture, whether as liquid water or as ground moisture.

Waterproofing and drainage are both key to ensuring good moisture management at the foundation. Ground slopes, perimeter drainage and placing downspouts away from walls will help move water away from the foundation wall. Foundation walls should also be protected with a waterproofing membrane.





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Course Summary





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Moisture Management

Managing moisture in walls is important because moisture can lead to severe problems like structural failure and mold growth as well as visual issues.

Moisture damage often goes undetected until major problems occur, but it is just as severe an issue as fire protection and structural integrity.

It is important to construct walls correctly in the first place because moisture damage can be difficult and expensive to fix. The key to good performance is correct installation of moisture management products.

Moisture can get into walls from both the exterior and interior. It can enter from the exterior as liquid water, usually due to precipitation, or it can enter from either side as vapor.





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Preventing Moisture Problems: The 4 D’s

There are four key strategies to preventing moisture damage called the four D’s. They should be used simultaneously to ensure that the wall is protected.

Deflection prevents moisture from getting to the wall in the first place by directing the water away. Examples include roof overhangs, gutters, drip edges and rainscreens.

Drainage prevents water from becoming trapped by moving it out quickly. An example is a drainage plane between the cladding and the sheathing.

Drying is the mechanism by which moisture is removed from the walls. It is mostly influenced by the composition of the wall assembly and the choice of materials.

Durability is the final line of defense. It refers to the walls tolerance to moisture and ensures that if moisture does end up getting into the wall, there is some leeway before problems occur.





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Moisture Management Products

Building wrap helps manage moisture in the wall by acting as a barrier against liquid moisture and air infiltration, while allowing vapor within the wall to escape. Proper installation of building wrap is essential for it to function as intended.

Flashing helps drain water out of the wall. It is used at openings such as windows and doors, at sill plates, at roof to wall intersections, etc. Proper installation of flashing is essential as is the correct detailing of flashing to building wrap joints.





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Wall Assembly Drainage Details

Wall assembly details depend on several factors including the method of construction, the specific climate zone and the cladding material. However it is important to have a continuous drainage layer between the cladding and the sheathing. It is also important that the wall is properly flashed at the sill and at any openings.





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Other Considerations

New types of sheathing, like XPS board, act as building wrap and sheathing in one lightweight and easy to install product.

It is also important to manage moisture at the roof and at the foundations as these are also sites for potential moisture problems.





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©2006, 2016 Kingspan Insulation LLC. The material contained in this course was researched, assembled, and produced by Kingspan Insulation LLC and remains their property. Questions or concerns about the content of this course should be directed to the program instructor. This multimedia product is the copyright of AEC Daily.

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Moisture Management in Walls - AEC Daily · Moisture Management in Walls Presented By: ... • define the products that help manage moisture in a wall and how to ... press the ESC