Maria Spinu, PhD, LEED AP DuPont Building Innovations Feb. 25, 2014

BALANCING ENERGY EFFICIENCY AND

DURABILITY

Maria Spinu, PhD, LEED APDuPont Building Innovations

Feb. 25, 2014

1. Recent trends in NA energy codes and changes in wall assembly design

2. Introduction to moisture simulation tools

3. Climate specific moisture analysis using WUFI simulations

I. Cold climates (cz 5-8)

II. Warm-Hot Humid climates (cz 1A-4A)

III. Marine climates (3C-5C)

OUTLINE

© E. I. DuPont de Nemours and Company 2013. All rights reserved

Section 1

Recent trends in NA energy codes and changes in wall assembly design


ENERGY EFFICIENCY DURABILITY

MANAGE THERMAL

Air leakage control Thermal Insulation

MANAGE MOISTURE

Minimize Wetting Maximize Drying

ENERGY EFFICIENCY AND DURABILITY

Potential Impact


SECTION 1SECTION 1

Air Infiltration Requirements [cfm/ft2 @ 0.3 in w.g., 75Pa]

Materials(ASTM E2178)

Assemblies(ASTM E2357 or

E1677)

Whole Building (ASTM E779)

NBC (National Building Code of Canada, 1990) 0.004 -- --

Massachusetts, Minnesota, New Hampshire, Georgia, Oregon, Washington, New York, etc…

0.004 -- --

ASHRAE 90.1 (2010) 0.004 0.04 --

USACE(2008); NAVFAC (2011) 0.004 -- 0.25

Washington State (2010) 0.004 -- 0.25

GSA (2010) USAF (2011) 0.004 0.04 0.40

ASHRAE189.1 (2009) IECC (2012) 0.004 0.04 0.40

IgCC (2012) -- -- 0.25

or

Abbreviations: ASHRAE – American Society of Heating, Refrigeration and air Conditioning Engineers; USACE - US Army Corps of Engineers; GSA - General Services Administration; NAVFAC - Naval Facilities Engineering Command; USAF- United States Air Force; IgCC – International Green Construction Code

or AND

or

AND

or

AIR LEAKAGE CONTROL: NA AIR BARRIER STANDARDS


SECTION 1

AIR BARRIER PRODUCT OPTIONS

Fluid Applied Membranes

<0.1 - 36 Perms

Self-Adhered Membrane

<0.01 - <1 Perms

Mechanically Fastened

<0.1 - 50 Perms● Vapor Permeable:

>10 Perms1

− The higher the Perms, the more vapor permeable the material, the higher the water vapor diffusion

● Vapor Retarders: ≤ 10 Perms

( Class I: 0.1 Perm or less

( Class II: 0.1< Perm≤ 1.0

( Class III: 1.0 <Perm≤101 2009 /2012 International Building Code (IBC): Vapor Permeable materials must have a moisture vapor permeance rating of 10 perms or greater… using Procedure A of ASTM E96.

Spray Polyurethane Foam (SPF)

<1.0 – 2.3 Perms

Many Air Barrier materials are vapor non-permeable & may be UNINTENDED Vapor

Barriers


SECTION 1

Climate Zone

Min. R-Value: Non-ResidentialIECC

Min. R-Value: Non-Residential ASHRAE 90.1

2006 2009 2012 2004 2007/2010 2013

1R-13.0 R-13.0 R-13 + R-5ci R-13.0 R-13.0 R-13.0

2R-13.0 R-13.0 R-13 + R-5ci R-13.0 R-13.0 R-13 + R-3.8c.i.

3R-13.0 R-13 + R-3.8c.i. R-13 + R-7.5ci R-13.0 R-13 + R-3.8c.i. R-13 + R-5.0c.i.

4R-13.0 R-13 + R-7.5c.i. R-13 + R-7.5c.i. R-13.0 R-13 + R-7.5c.i. R-13 + R-7.5c.i.

5R-13 + R-3.8c.i. R-13 + R-7.5c.i. R-13 + R-7.5c.i. R-13 + R-3.8c.i. R-13 + R-7.5c.i. R-13 + R-10.0c.i.

6 R-13 + R-3.8c.i. R-13 + R-7.5c.i. R-13 + R-7.5c.i. R-13 + R-3.8c.i. R-13 + R-7.5c.i. R-13 + R-12.5c.i.



CONTINUOUS INSULATION REQUIREMENTS (Steel-framed walls; IECC & ASHRAE 90.1)

c.i. = continuous insulation, uninterrupted by structural members © E. I. DuPont de Nemours and Company 2014. All rights reserved

SECTION 1

BENEFITS OF CONTINUOUS INSULATION

CONTINUOUS INSULATION (c.i.): insulation that is installed outside the structural members, without thermal bridges other than fasteners and service openings. IT IS NOT TAPED INSULATION!

IMPROVE THERMAL PERFORMANCE:+ INCREASE OVERALL R-VALUE

+ REDUCE THERMAL BRIDGING

THERMAL BRIDGES are regions of relatively high heat flow conductance in a BE (e.g. steel studs)

SECTION 1


R-value: ~4 R/inPermeability: 54 perm-in

Source: 2009 ASHRAE Handbook-Fundamentals * 1997 ASHRAE Handbook-Fundamentals

CONTINUOUS INSULATION PRODUCT OPTIONS● Mineral Wool Fiber Board

R-value: ~6 R/in (HD)*Permeability: 1.9 perm-in

● Spray Polyurethane Foam (SPF)

R-value: ~6 R/in Permeability: 0.75 perm-in

● Polyisocyanurate


● EPS (Expanded Polystyrene)


● XPS (Extruded Polystyrene)

MOST INSULATION MATERIALS ARE VAPOR NON-PERMEABLE AND MAY BE UNINTENDED VAPOR BARRIERS © E. I. DuPont de Nemours and Company 2014. All rights reserved

SECTION 1

EXULATION

Non

-insu

late

dCo

nditi

oned

Cav

ity

HYBRID/

SPLIT INSULATION

CAV

ITY IN

SU

LATIO

N

EX

TER

IOR

IN

SU

LA

TIO

N (

ci)

TRADITIONAL

No longer meets Energy Codes in most climates2

Energy CodesCompliant, all climates

Could meet Energy Codes (constructability/insulation thickness)

2Except for climate zone 1, per ASHRAE 90.1-2010

Air

/Wate

r B

arr

ier

Air

/Wate

r B

arr

ier

CAV

ITY IN

SU

LATIO

N

EX

TER

IOR

IN

SU

LA

TIO

N (

ci)

1Steel Framed Wall Design

Vap

or

Barr

ier/

Reta

rder*

Vap

or

Barr

ier/

Reta

rder*

Air

/Wate

r B

arr

ier

* Climate specific code requirement © E. I. DuPont de Nemours and Company 2014. All rights reserved

CHANGES IN WALL ASSEMBLY DESIGN FOR CODE COMPLIANCE1

SECTION 1

Section 2

Moisture simulation tools


● DEW POINT ANALYSIS

● WUFI® (Wärme Und Feuchte Instationär or Transient Heat and Moisture Transport)

● ASHRAE Standard 160: Criteria for Moisture-Control Design Analysis in Buildings


MOISTURE ANALYSIS TOOLS

SECTION 2

RAIN (SNOW)(above grade envelope) >>1,000X

AIR CURRENTS

1XDIFFUSION

100X

BU

LK

WATER

98%

2%

1

2

3

WATER

VA

PO

R


WUFI can simulate impact of all moisture sources

Dew Point analysis can only simulate impact of vapor diffusion

RATING OF MOISTURE SOURCES IN BUILDINGS

SECTION 2

● Dew Point analysis is based on vapor diffusion equations ONLY (remember, diffusion is the smallest source of moisture!)

DEW POINT ANALYSIS

● WUFI simulations use hourly data, not a single point

● Dew Point analysis assumes steady-state conditions (equilibrium conditions) – one point in time, while actual conditions change

● Dew Point analysis determines the dew point location in the assembly, at ONE POINT in time (coldest day of the year)

● WUFI simulations can assess:

1) Hourly condensation potential due to vapor diffusion AND air leakage, in ANY layer, throughout the year

2) The drying rates following incidental water intrusion

3) Condensation due to solar driven moisture

● WUFI simulations are based on vapor diffusion and liquid transport equations

WUFI SIMULATIONS vs.


DEW POINT vs. WUFISECTION 2

(Using Dow Software)

Dew Point Temperature

Actual Temperature

DEW POINT Dew Point Location in the Wall Assembly, under equilibrium

conditions


ONE POINT IN TIME

EXAMPLE -- DEW POINT ANALYSIS (DEW POINT LOCATION WITHIN THE WALL)

SECTION 2

MOISTURE TRANSPORT EQUATIONS

HEAT TRANSPORT EQUATIONS

Construction

details:e.g.

orientationinclination, height, etc.

Initial conditions:e.g. construction

moisture

Climate conditions:

e.g. Temperature, RH, radiation,

precipitation, wind speed & direction

Material properties:

e.g. Density, porosity, heat capacity, thermal

conductivity, permeability

http://www.ornl.gov/sci/btc/apps/moisture/ibpe_sof161.htm

Developed by Fraunhofer Institute for Building Physics (IBP) and Oak Ridge National Laboratory (ORNL); coupled heat & moisture transport simulation models

© E. I. DuPont de Nemours and Company 2014. All rights reservedHOURLY TEMPERATURE & MOISTURE PROFILES ACROSS ASSEMBLY

WUFI SIMULATIONS

SECTION 2



EXAMPLES -- WUFI ANALYSIS (HOURLY DATA, EVERY LAYER)

HOURLY CONDENSATION POTENTIAL DUE TO DIFFUSION

MOISTURE ACCUMULATION COMPARISON

DRYING RATES COMPARISON


SECTION 2

HOURLY CONDENSATION POTENTIAL DUE TO AIR LEAKAGE

Section 3

WUFI Simulations – Climate Specific Moisture Analysis


US COLD CLIMATES (CZ 5-8)

Same questions, climate & design specific solutions!

http://www.energycodes.gov/implement/pdfs/color_map_climate_zones_Mar03.pdf

1. Condensation Risks: What is the main risk of condensation, air leakage or vapor diffusion?

2. Drying Rates: What factors affect the drying rates following incidental moisture intrusion?


SECTION 3

http://www.energycodes.gov/implement/pdfs/color_map_climate_zones_Mar03.pdf

● Exterior climate: Chicago, IL (cz 5A)

● Interior design parameters: 69.8 ± 1.8oF; 50±10% RH (Medium moisture loads)

● Steel-framed, split insulation wall design: R-13 + R-7.5 ci– per IECC 2012 cz 5

● Air /Water Barrier (WRB): 25 Perms (Vapor Permeable DuPontä Tyvekâ WRB)

● Vapor Retarder*: Class I, II & III

● Exterior insulation: XPS, MW

● Short-wave Radiation Absorptivity for red brick (0.68) (solar driven moisture)

● Three-year simulation period

R-7

.5 E

xte

rior

ci

R-1

3 C

avit

y insu

lati

on

Bri

ck E

xte

rior

claddin

g

2”

Air

sp

ace

/50

AC

H

Air & Water Barrier Vapor Retarder

Code Compliant, Hybrid Wall Design

COLD CLIMATES WUFI SIMULATIONS

SIMULATION PARAMETERSCODE COMPLIANT WALL (Steel frame construction, cz 5)

* Class I, II or III Vapor Retarders required in cz 5-8© E. I. DuPont de Nemours and Company 2014. All rights reserved

Traditional Exulation

● Hybrid wall design compared with traditional and exulation walls

SECTION 3

VAPOR BARRIER REQUIREMENTS: 2009/2012 IBC

Class I: 0.1 perm or less Class II: 0.1 < perm ≤ 1.0 perm Class III: 1.0 < perm ≤10 perm

NO VAPOR RETARDERS ARE REQUIRED IN CZ 1-4 (EXCEPT 4C)© E. I. DuPont de Nemours and Company 2014. All rights reserved

SECTION 3

MOISTURE RISKS ASSESSMENT

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

Coole

r Su

rface

s

InteriorExterior

POTENTIAL CONDENSATION

Interior(Warm-humid)

Exterior

INTERIOR AIR DEW POINT

Coole

r Su

rface

s

POTENTIAL CONDENSATIONA

ir B

arr

ier

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

A. CONDENSATION FROM DIFFUSION

vs. B. CONDENSATION FROM AIR EXFILTRATION




SECTION 3

Climate: Chicago, IL (cz5) Wall Design: Hybrid, XPS ci

● WITH NO VAPOR RETARDER OR HIGHER PERMS CLASS III VAPOR RETARDER, THERE IS CONDENSATION RISK DUE TO VAPOR DIFFUSION DURING WINTER

● IBC 2012 REQUIRES VAPOR RETARDERS TO PREVENT DIFFUSION WETTING DURING WINTER

1A. CONDENSATION RISKS DUE TO VAPOR DIFFUSION (ESTIMATE MOISTURE CONTENT IN EXTERIOR SHEATHING)

GB Equilibrium Moisture Content


SECTION 3

Climate: Chicago, IL (cz5) ; Wall Design: Hybrid, XPS ci

1B. CONDENSATION RISKS DUE TO AIR LEAKAGE(ESTIMATE MOISTURE CONTENT IN EXTERIOR SHEATHING)

Steel Stud Ext. Surface T

Dew Point Tof Interior Air

Interior air

Dew Point

Compare steel stud ext. surface T with dew point T of exfiltration air

IF AIR EXFILTRATION REACHES THE STUD SURFACE THERE IS RISK OF CONDENSATION: The stud T is below the dew point T of exfiltration air


SECTION 3

● There is low potential for condensation from VAPOR DIFFUSION (when wall assembly is built to code – Class I, II or III VR)

● AIR EXFILTRATION is the major source of condensation during winter months

If air exfiltration reaches the exterior cooler layers

Repeated condensation coupled with low drying rates could lead to moisture problems

● Air leakage can be prevented/minimized with a continuous air barrier

1. DIFFUSION vs. AIR LEAKAGE


SECTION 3

MOISTURE RISKS ASSESSMENT

Drying rates can be estimated by starting the simulation with wet exterior sheathing (e.g. 15.6 lb/ft3 or 250 kg/m3) and observing the drying curves of the wetted layer

Stu

cco c

lad

din

g

Air & Water Barrier Vapor Retarder

Wet

Exte

rior

GB




SECTION 3

DRYING POTENTIAL COMPARISON FOR THE 3 WALL ASSEMBLIES (CLIMATE ZONE 5A, CHICAGO, IL)

HYBRID (Split Insulation)

START WITH HIGH MOISTURE CONTENT IN EXTERIOR SHEATHING: 15.6 lb/ft3 or 250 kg/m3

XPS

& M

W

WRB: 25 & 0.1 Perms/VB 1 & 10 Perms

R-1

3

R-7

.5ci

TRADITIONAL

R-1

9

WRB: 25 Perms/ VB: 1 Perm

EXTERIOR INSULATION (Exulation)

R-1

5

WRB: 25 Perms/ No VB


SECTION 3

HYBRID WALLS DRY VERY SLOW:

1. Energy efficient assemblies dry inherently slower

2. However, materials choices could have a significant impact: DOUBBLE VAPOR BARRIER

COMPARATIVE DRYING RATES FOR 3 WALL ASSEMBLY DESIGN OPTIONS

Chicago, IL; 3 Wall Design Options; 25 Perms WRB; 1Perm VR; XPS ci


SECTION 3

IMPACT OF VAPOR PERMEANCE OF EXTERIOR LAYERS (ci) ON THE DRYING RATES

XPS vs. MW; Chicago, IL; Hybrid Wall; 1Perm VB; Vapor Permeable WRB

HYBRID WALLS WITH VAPOR PERMEABLE EXTERIOR LAYERS ACHIEVE HIGH DRYING RATES

TRAPPED MOISTURE & SLOW DRYING RATES DUE TO DOUBLE VAPOR BARRIER (XPS & 1PERM INTERIOR VB)


SECTION 3

IMPACT OF WRB VAPOR PERMEANCE ON THE DRYING RATES

0.1 Perms WRB

25 Perms WRB

WALLS W/VAPOR PERMEABLE EXTERIOR LAYERS HAVE HIGH DRYING RATES

Chicago, IL; Hybrid Wall; MW ci, 1Perm VB;

0.1Perms & 25 Perms WRB TRAPPED MOISTURE /SLOW DRYING RATES DUE TO DOUBLE VAPOR BARRIER


SECTION 3

DRYING RATES & MOISTURE RISKS

● If a wall is able to dry it can experience some wetting without long-term durability risks

● THE KEY TO MOISTURE MANAGEMENT: Minimize the risk of wetting and ALWAYS consider drying pathways


SECTION 3

IMPACT OF VENTING ON THE DRYING RATES

10 mm airspace behind XPS, 20 ACH

No airspace behind XPS, 0 ACH

3 mm (1/8”) airspace behind XPS, 20 ACH

Venting behind cladding

Venting would make it acceptable to use XPS c.i.

OPTIMUM SIZE? -- EIFS INDUSTRY

Venting behind XPS

XPS

Chicago, 25 Perms WRB, 1 Perm VB


SECTION 3

DRAINAGE BEHIND XPS BOARD IS CRITICAL FOR DRYING

Drainage Rate vs. Drainage Gap

0

500

1000

1500

2000

2500

3000

3500

4000

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Drainage Gap (mm)

Dra

ina

ge

Ra

te (

ml/h

r/c

m)

1.8 mm = 1/16in

WRB w/drainage channels allows draining and could

provides some venting*

* No experimental data are available at this time to confirm venting through the drainage channels of drainable WRB


SECTION 3

Q1: What is the role of the beer caps on the XPS board?

A1: To create an airspace between WRB/Air Barrier and the vapor impermeable insulation Board, in order to facilitate drying

Q2: What else do you need in this airspace?

A2: Venting!

Q3: What can help create some venting in this airspace?

A3: Un-taped joints for XPS or any vapor impermeable insulation board

JOKING ASIDE, THIS IS A VERY IMPORTANT MESSAGE!

Picture: Maria SpinuSource: Joseph Lstiburek, PhD -- 2013 Summer Camp


MINIMIZE IMPACT OF DOUBLE VAPOR BARRIERS IN WALL ASSEMBLIES

SECTION 3 SUMMER CAMP FUNNIES

XPS Board

Venting behind cladding and vapor impermeable board insulation

XPS

WRB/Air Barrier

E x t e r i o r S h e a t h i n g

Drainable WRB

E x t e r i o r C l a d d i n g

XPS joints should not be taped


VENTING BEHIND VAPOR IMPERMEABLE INSULATION BOARD: CRITICAL FOR DRYING

SECTION 3

DRYING OF CONSTRUCTION MOISTURE (CMU WALLS)

SIMULATION PARAMETERSCMU WALL W/ CONSTRUCTION MOISTURE

● Exterior climate: cz 5A (Chicago, IL)

● Interior design parameters: 69.8 ± 1.8oF; 50±10% RH (Medium moisture loads)

● CMU back-up wall: 2” MW ci

● Vapor Retarder: 10 Perms (Class III)

● Air/Water Barrier: 25 Perms & 0.1 Perms

● Short-wave Radiation Absorptivity for red brick (0.68) (solar driven moisture)

● Rainscreen wall design, 2” airspace, ventilated cladding (50ACH behind cladding)

SECTION 3

Bri

ck

Wet CMU

Air

sp

ace

WR

B

10 P

erm

s

2” M

W

Air & Water BarrierVapor Barrier

(25 & 0.1 Perms)


SECTION 3SECTION 3

DRYING OF CMU CONSTRUCTION MOISTURE

Year 1 Year 2 Year 3

CONSTRUCTION MOISTURE DRIES FASTER WITH VAPOR

PERMEABLE WRB (25 PERMS)

0.1 Perms FA WRB

25 Perms FA WRB

CONSTRUCTION MOISTURE DRIES VERY SLOW WITH VAPOR IMPERMEABLE WRB (0.1 PERMS)

Chicago, IL; CMU Wall; MW ci; 0.1Perm & 25 Perms WRB; 10 Perms Vapor Retarder


● Moisture intrusion coupled with slow drying rates could lead to moisture damage and long term durability issues

● Drying rates are affected by:

− Materials choices: need vapor permeable materials to allow drying

− Venting behind cladding essential for effective drying rates

− Venting behind vapor impermeable continuous insulation is also essential for drying


2. FACTORS AFFECTING DRYING RATES

SECTION 3

MOISTURE CONCERNS DESIGN CONSIDERATIONS1. Condensation Risks:

What is the main risk of condensation, air leakage or vapor diffusion

Vapor Retarders Class I, II or III are required by code, to minimize wintertime condensation due to vapor diffusion

2. Drying Rates: Factors affecting the drying rates

SUMMARY COLD CLIMATES

Drying in cold climates require:− Vapor Permeable exterior layers (WRB, continuous

insulation)

− Venting behind cladding

Continuous Air Barriers are critical to prevent condensation due to air leakage

Vapor impermeable continuous insulation (ci): − Creates double vapor barriers leading to moisture

accumulation and moisture damage

− Venting behind vapor impermeable ci board is one way to allow some drying of incidental water intrusion


SECTION 3

Due to the inherent limitations of the WUFI model, SIMULATION RESULTS REPRESENT RELATIVE

PERFORMANCE OF BUILDING ASSEMBLIES AND NOT QUANTITATIVE PREDICTIONS OF THE MATERIALS'

MOISTURE CONTENT. The trends in moisture accumulation and drying rates for

different design options provide useful relative performance information.

DISCLAIMER

The examples provided apply to SPECIFIC CLIMATE AND WALL DESIGN and the conclusions do not automatically apply to other climates/wall designs. However, these examples demonstrate the value of moisture analysis in

comparing different design options.

SECTION 3

This concludes the American Institute of Architects Continuing Education Systems Program

[email protected]

mailto:[email protected]

Documents

Maria Spinu, PhD, LEED AP DuPont Building Innovations Feb. 25, 2014