Presented by: W. R. MEADOWS

Welcome

Controlling Moisture Movement In Buildings

The Complete Approach

Air Barriers

Building strength through Building strength through educationeducation

This program is registered with the 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. Thank you!

Learning Objectives Identify moisture sources and their methods of transport through the

building envelope

Differentiate between an air barrier and vapor retarder

Identify several design options available to help prevent the intrusion of moisture into a building

Identify how air and vapor barriers contribute to overall energy savings, indoor air quality and occupant comfort

Identify the importance of air barriers in a structure and how they can contribute to building sustainability

How Does Moisture Enter Our Buildings?

Large droplets (Rain/Sleet Snow)Wall design

Water in vapor form (above and below grade) by diffusion

Vapor barriers/Retarders (above and below grade)

Small droplets carried in the airAir barriers

Ground waterWaterproofing

Moisture Movement Above Grade

Air pressure differential

Vapor diffusion

Moisture movement by air:

Accounts for 70-90% of the moisture through the building envelope.

10-30% of moisture is moved by vapor diffusion.

Wall Design - Components

Structural Façade Heat Barrier Moisture Barrier/Drainage Plane Vapor Barrier/Retarder Air Barrier

Weather Enclosure System

Heat BarrierResists thermal transfer through the building enclosure system

Air BarrierStops the free flow of air through the building enclosure

Vapor Barrier/RetarderReduces wetting potential due to vapor diffusion into and through the building enclosure system.

Moisture Barrier/ Drainage PlaneReduces wetting potential due to liquid moisture intrusion into and through the building enclosure system

Wall Design - Components

Placement of Components is Critical

Effective Walls Have Drying PotentialEffective Walls Have Drying Potential

Air Leakage and Moisture Movement

As early as the 1950’s it was becoming clear that air leakage was instrumental and common to the majority of building envelope problems and failures. It was instrumental in rain penetration, condensation problems, excess heat loss, drafts etc.

Remember…Air leakage can account for as much as 70-90% of moisture moving through the building envelope, while vapor diffusion can account for only 10-30%.

Vapor Barriers

Reduce the transmission of moisture in it’s vapor form by diffusion (small amounts above grade, large amounts below) INDEPENDENT OF AIR PRESSURE

Diagram Courtesy of buildingscience.com

Air Barriers and Moisture Control

Air Barriers

Any material that is able to prevent the movement of air under pressure through it

Also block the movement of any moisture that air is carrying

Diagram Courtesy of buildingscience.com

Air Barriers and Moisture Control

A masonry wall leak?

Air Barrier System

What is an Air Barrier System?

A system of building assemblies within the building enclosure—designed, installed and integrated in such a manner as to stop the uncontrolled flow of air into and out of the building enclosure.

The air barrier membrane is an integral part of this system.

Why use Air Barrier Systems?Why use Air Barrier Systems?

The U.S. Government and several states support and promote the usage of air barrier systems on commercial building projects for some of the following reasons:

• DOE has determined that up to 40% of a building’s energy consumption to heat and/or cool the building is due to air leakage

• DOE has instituted a program of goals to reduce building energy consumption by 25% by the year 2010 and by 50% by the year 2020

A study of findings by the National Institute of Standards and Technology (NIST) show that inclusion of an air barrier system in non-residential buildings can:

• reduce air leakage by up to 83%• provide potential gas savings of greater than 40% • result in electrical savings of greater than 25%

Benefits and Advantages of Air Barrier Systems

• Reduced building enclosure system problems

• Wetting potential effectively dealt with

• Improved indoor air quality

• Reduced fossil fuel consumption

• Reduced carbon dioxide emissions

• Reduction of the greenhouse effect

• Improved occupant comfort

WIND PRESSURE

FAN PRESSURE

WIND PRESSURE

( UNDER SUCTION)

PLENUM EFFECT

AIR PRESSUREPLENUM EFFECT

AIR PRESSURE

STACK PRESSURE

STACK PRESSURE

Building Pressures

• Wind Pressure

• Fan Pressure

• Stack Pressure

Inattention to the building envelope leads to…..

Leaks Corrosion of metal components Degradation of components Mold Poor indoor air quality Increased loads on HVAC systems

resulting increased building energy costs

Uncontrolled air leakage in a building envelope

Excess moisture in exterior walls causes:Excess moisture in exterior walls causes:

The “ M “ WordThe “ M “ Word

Essential elements of an effective Air Barrier System

Airtightness

Continuity

Durability

Structural integrity

Factors influencing the effectiveness of an Air Barrier System

Design

Materials

Workmanship

Quality assurance

Effective Air Barrier Systems Materials Should:

Have an air permeability rating not exceeding of 0.004 cfm/ft2

(0.02 L/S.m2) under a pressure differential of 1.57 lbs/ft2 (75Pa)

Be capable of withstanding positive and negative wind, fan and stack pressures

Be durable and maintainable

Be continuous with all joints, laps, and seams airtight

Be flexible in nature to allow for different substrate movements, expansions and contractions

Vapor barriers are materials used in Building EnclosureVapor barriers are materials used in Building EnclosureSystems to retard the diffusion of vapor into and through Systems to retard the diffusion of vapor into and through the building enclosure system.the building enclosure system.

Why Are Vapor Barriers Needed?Why Are Vapor Barriers Needed?

By retarding the diffusion of vapor through the Building By retarding the diffusion of vapor through the Building Enclosure System, conditions that create dew points within Enclosure System, conditions that create dew points within Building Enclosure Systems can be reduced or prevented Building Enclosure Systems can be reduced or prevented and interior RH levels can be maintained.and interior RH levels can be maintained.

The Vapor Barrier/RetarderThe Vapor Barrier/Retarder

Vapor Movement - General

From warm to cool From high pressure to low pressure

What is Vapor Diffusion ?

Vapor diffusion is the process by which vapor seeks to equalize Vapor diffusion is the process by which vapor seeks to equalize its content between different environments ( the Ideal Gas Law ).its content between different environments ( the Ideal Gas Law ).

The driving force ( or “potential” ) for this occurrence is vapor The driving force ( or “potential” ) for this occurrence is vapor pressure which is a function of the vapor content of the air (RH) pressure which is a function of the vapor content of the air (RH) and the temperature.and the temperature.

Vapor diffusion is caused by a vapor pressure differential ( ∆P ) Vapor diffusion is caused by a vapor pressure differential ( ∆P ) between different environments. The greater the ∆P between between different environments. The greater the ∆P between environments, the greater the amount of vapor diffusion that environments, the greater the amount of vapor diffusion that occurs.occurs.

The Dew PointThe Dew Point

The dew point is the temperature at which air The dew point is the temperature at which air that contains a certain amount of vapor can no that contains a certain amount of vapor can no longer hold that vapor and must exhaust itself longer hold that vapor and must exhaust itself of excess vapor by depositing it on adjacent of excess vapor by depositing it on adjacent surfaces in the form of condensation ( water ).surfaces in the form of condensation ( water ).

Incorporation of the vapor retarder impacts Incorporation of the vapor retarder impacts where the dew point forms.where the dew point forms.

Where does the water on the Where does the water on the outside of the glass come from?outside of the glass come from?

EXAMPLE 1: If the interior air temperature is 70˚ F and has an RH of 30%, the infiltration of air that is 37˚ F ( the dew point temperature ) can cool condensing surfaces to this temperature ( 37 ˚ ) causing dew to form on these surfaces.

EXAMPLE 2: If exterior air with a temperature of 90˚ F and an RH of 80% infiltrates into the building envelope, dew will form on condensing surfaces in the system that have temperatures of 83˚ F or less.

Dew Point Calculator

Moisture Barrier/ Drainage Plane

Impermeable

Prevents the penetration to the interior of liquid water from exterior sources and drains it from the wall cavity to the outside

Permits drainage to the exterior of any condensation within the wall cavity to the exterior

Moisture Barrier/ Drainage Plane

Vapor Permeable

Typical wall section as found in the following climate types: Mixed-humid Hot-humid Hot-dry

Drainage plane is a vapor permeable layer

Barrier Membranes Control moisture movement by air leakage Control moisture movement by vapor diffusion Control moisture movement due to precipitation

Can be separated into one of four general classes based on permeance: vapor impermeable: 0.1 perm or less vapor semi-impermeable: 1.0 perms or less and greater than 0.1

perm vapor semi-permeable: 10 perms or less and greater than 1.0 perm vapor permeable: greater than 10 perms

Air / Vapor Barriers and Vapor Permeable Air Barriers

What is an Air/Vapor Barrier?

A single material that performs three separate and discrete critical functions in the building envelope:

Air Barrier Vapor Barrier Moisture Barrier/Drainage Plane

Vapor Permeable Air Barriers

Acts as an air barrier and moisture barrier/drainage plane

Allows walls to be permeable May require separate vapor barrier

Used in specific climates and specific wall systems

Vapor Permeable Air Barriers

Deciding factors when choosing vapor permeable membranes include:

Building use (present and future) Climate zone Wall make-up Code requirements

Hygro-Thermal Regions

Defined by number of heating/cooling days

Rainfall

Putting it all togetherWalls that work today

Air barrier Vapor barrier

Beware the double vapor barrier Interior finish Choice of insulation

Moisture barrier

Remember…an effective wall assembly must have the ability to dry

All Climates*

* Special building types or some buildings with controlled environments will need further analysis

The Perfect Wall

A More Cost-effective Wall System

What is the R-value of this wall?

Pick the best response: At least R11

At least R12

At least R13

None of the above

R-12 Fiberglass Batt

4” Steel Stud

Gypsum Drywall

Thermal Performance Steel StudsEffective R Value

ComponentInt air filmGypsumR12 battGypsumExt.air filmEffective:

R-value0.680.455.760.450.177.51

Wall System – Cost Effective

Types of Air and Air/Vapor Barrier Materials

Elastomeric bitumens and Synthetic rubber-based Mastic

Among the first used after required by code

May also act as insulation adhesive

Types of Air and Air/Vapor Barrier Materials

Torch-grade membranes

Also an early entry into the AVB Market

Adapted from SBS roofing technology

Types of Air and Air/Vapor Barrier Materials

Spray in place Urethane foam (SIPU)

Intended to provide Air Barrier, Vapor Retarder and Thermal Barrier

Types of Air and Air/Vapor Barrier Materials

Self-adhering (Peel and Stick) membranes

Uses SBS modified asphalts laminated to high-density cross-laminated polyethylene

Types of Air and Air/Vapor Barrier Materials

Peel and no Stick

Application of Air/Vapor Barriers

Labor component is the major cost factor on any project involving any product

Proper application is the key to a successful Building Envelope System

Every product has its own application and performance issues

Sheet Goods - Application

Remove mortar droppings

If it has rained let wall dry – two days?

Prime wall Apply membrane Detail ALL TIES

Liquid Applied – Rubberized Asphalt Emulsion

Remove mortar droppings – possiblypossibly

If it has rained let wall dry – no needno need

Prime wall – not req.not req. Apply membrane Detail ALL TIES – done done

at time of liquid at time of liquid applicationapplication

Testing the Thickness

Not all liquids systems are created equal, choose

carefully

Liquid Membranes- Key Differences

Does the membrane self seal? Acrylics formula dependant check with manufacturer Rubberized asphalt yes

Early rainfall resistance Acrylics poor Rubberized Asphalt good (depending on formula)

Does the system contain a corrosive accelerators? Do you want them near your metal components in a wall?

Designed to reduce the overall impact of the built environment on human health and the natural environment.

• efficient use of energy, water and other natural resources

• protecting occupant health and improving employee productivity

• reducing waste, pollution, and environmental degradation

Sustainability can be defined as maintaining a balance of a certain process. For humans, the earth's resources must be used at a rate where they can be replenished.

Green building and sustainability go hand in hand.

Green Buildings & SustainabilityGreen Buildings & Sustainability

• developed by the USGBC

• provides a benchmark for green building that is nationally accepted for the design, construction, and operation of buildings

• provides a WHOLE building approach to sustainability

• originally broken down into six categories consisting of Prerequisites and Credits and the number of points that a building obtains, determines a level of LEED Certification for that building.

• revised in 2009, now 7 categories and re-weighting of the categories

• incorporation of an air and vapor barrier within the building envelope can contribute to overall energy efficiency and occupant comfort, and can also help obtain credits in the categories listed on the following slide.

LEEDLEED®®

Energy and Atmosphere (EA)

Prerequisite 2: Minimum Energy Performance Credit 1: Optimize Energy Performance (1-10 points)

Materials and Resources (MR)

Credit 5.1/5.2: Regional Materials 10% or 20% Extracted and Manufactured Regionally

Indoor Environmental Quality (EQ)

Prerequisite 1: Establish Minimum IAQ PerformanceCredit 3.1: Construction IAQ Management PlanCredit 4.2: Paints and CoatingsCredit 7.1: Thermal Comfort Design

LEEDLEED®®

In Summary

Your wall will get wet where you didn’t intend it to…design for it!

When it gets wet….let it dry Wind will try to blow into your building Suction will pull conditioned air out of your

building

Good design above grade will require;

An Air Barrier System A Moisture Barrier System

And may require An effective Vapour Barrier

AIR BARRIER ASSOCIATION OF AMERICAAIR BARRIER ASSOCIATION OF AMERICA

www.airbarrier.orgwww.airbarrier.org

DETAILS, EDUCATION AND QUALITY ASSURANCEDETAILS, EDUCATION AND QUALITY ASSURANCE

Downloadable and editable air barrier system specificationDownloadable and editable air barrier system specification

Best practice air barrier detailsBest practice air barrier details

Industry standards and testing protocolsIndustry standards and testing protocols

Educational resourcesEducational resources

Quality Assurance programsQuality Assurance programs

Licensed installersLicensed installers

Certified contractorsCertified contractors

Contact information for consultants and certified installersContact information for consultants and certified installers

Thank you!

Questions?

This concludes the credit portion of the program for The American Institute of Architects Continuing Education System

For additional information, contact: INSERT NAME INSERT EMAIL ADDRESS

800-342-5976

W. R. MEADOWS, INCwww.wrmeadows.com