mo2vaon, basics, examples manfred kehrer · wje powerpoint presentaon template 4 mo2vaon the sweden...

11/17/17

WJEPowerPointPresenta2onTemplate 1

HygrothermalBuildingPerformanceAssessmentinthe21stCentury

Mo2va2on,Basics,ExamplesManfredKehrer

Solu2onsfortheBuiltWorld Page1

MyBackground


11/17/17


WhatisHygrothermalEngineering?

Hygro-Thermal -  Heat -  Heat Transfer -  Insulation -  Thermal Conductivity -  Energy Savings -  Thermal Performance

-  Hygro (Greek) -  Moisture -  Moisture in the Air (Vapor) -  Moisture in Material (Moisture Content) -  Moisture accumulation -  Moisture problems?

Heat and Moisture are COUPLED!

-  Saturation Moisture in Air depends on Temperature -  R-Value depends on Moisture Content -  Etc.



Mo2va2onWhyHygrothermalEngineering?

“Ask the Enclosure!”

Ref. Blaich, EMPA

Algae growth on exterior insulation system caused by exterior condensation due to sky radiation

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Mo2va2onWhyHygrothermalEngineering?Frost damage of render

on masonry after interior insulation with foam glass


Mo2va2onWhyHygrothermalEngineering? Lime cement render

Wat

er c

onte

nt [V

ol.-%

]

Nov Dec Jan Feb Mar

with interior insulation without interior insulation

Critical Moisture content from frost dilatometry

Frost damage of render on masonry after interior insulation with foam glass

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Mo2va2onTheSweden“Experiment”


Ø EIFS on >20,000 buildings up until 2007. Ø 55% of the buildings had moisture damage in exterior wall(s) Ø 3.2 billion US$ estimated damage costs

Source: Samuelson & Jansson, 2009

>20xbigger

ImpactofThermalInsula2ononMoisture

No Cavity Insulation

Fibre Glass Insulation

Higher Temperature Gradient has the result that cold spots are closer to warm spots ð Higher condensation risk


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ImpactofAirTightnessonMoistureMoisturetransportduetoairinfiltra2onintotheenclosure Not Air Tight

Energy leak Warming of the leakage area in case of strong air flux ð Only a little condensation

Moisture leak Cooling of the air in case of slow and tortuous air flux ðMuch more condensation

Risky

„Air Tight“ Air Tight

Good luck!


ImpactofAirTightnessonMoistureResultofORNLstudiesaboutairflow


Drywall Fiber Glass OSB

Airflow Path

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RiskofMoistureDamage

NonEnergyEfficientEnclosureEnergyEfficientEnclosure

AStructuralAnalogon


#1Du2es

Themostimportantthingabuildingdoes?

->Standupright!

Themostimportantthingsabuildingenclosuredoes?

->Keepoutrainwater!


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BuildingsEnclosureschanged


4 out of 5 main articles deal with moisture

ImportanceofMoisture


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Vliet test building KULeuven

BEG hut Waterloo Canada

Field tests:

§ Very time consuming § Very expensive § Search for alternative ways to investigate

hygrothermal performance

PreviousAssessment

Fraunhofer IBP, Germany

Offices and laboratories

Original

test huts

Energy test

houses

Facade testing

hall

Asterix


IBP outdoor test site in Holzkirchen, Germany

Coconut beach in Hawaii: Field tests

§  limited transferability to another climate

PreviousAssessment


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Field test site in Bangkok Vliet test building KU Leuven, Belgium

BEG hut Waterloo Canada

Field tests: solution to climate dilemma

§ new test sites §  search for alternative ways to investigate

hygrothermal performance

PreviousAssessment


Laboratory tests: climate chambers (hot box / cold box)

§  realistic conditions, Temp., RH §  sky radiation and precipitation

difficult to simulate §  limited capacity § Time consuming §  expensive

PreviousAssessment


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HygrothermalModelingasanAddi2on,WUFI®


climate conditions

construction assembly material properties location, orientation

inclination

initial conditions

( )( )satp pDt

wφδφ

φ∂φ∂

φ ∇+∇⋅∇=∂

∂⋅

( ) ( )( )satpv phTtT

TH

φδλ∂∂

∇⋅∇+∇⋅∇=∂

∂⋅

Basics

monomulecular layer monomulecular layer

multimolecular layer

monomulecular layer


capillary condensation

monomulecular layer


capillary condensation

monomulecular layer


Moisture Storage

Sorption isotherm

§  Water molecules are adsorbed on the interior surfaces of porous materials

§  The higher the RH, the thicker the layer

§  When the RH in the pores decreases, water molecules evaporate from the molecular layer

Wat

er C

onte

nt

Relative Humidity [%]


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Basics


Vapor Vapor and liquid Liquid ϕϕ ∇⋅−= Dglp δg pv ∇−=

Moisture Transport

70 degF

50% RH Absolute

Humidity Relative Humidity

Outdoor Indoor

Example Flat Roof

TransientHygrothermalProcessesinBuildingEnclosure


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BasicsHowdoesdryingwork?


MaterialProper2esMeasurement


Heat and moisture analysis is complex. material properties can be approximated with the following rel. simple and standardized material properties:

❚  Density

❚  Porosity

❚  Heat Capacity ASTM (Calorimeter)

❚  Thermal Conductivity ASTM C518, C177

❚  Moisture Sorption Function ASTM C1498, C1699

❚  Water Vapor Permeability ASTM E96

❚  Water Absorption Coefficient ASTM C1794

11/17/17


Year

Wat

er C

onte

nt [

M.-%

] Charleston, SC

Germany

ModelValida2on,WUFI®Pro


ASHRAE160-2016

Purpose:Tospecifydesigncriteriaforpredic2ng,mi2ga2ng,orreducingmoisturedamagetothebuildingenclosure.


11/17/17


ASHRAE160-2016DrivingRainPenetra2on

„.... and nothing is perfect!“

ASHRAE 160 recommends to expect Water Penetration 1% of Driving Rain


New ASHRAE Criteria based on Mold Growth prediction

ASHRAE160-2016,ResultEvalua2on


11/17/17


ModelLimita2ons


ModelLimita2ons


§  Non-Orthogonal Structures §  More-dimensional structures §  Anisotropy §  Inhomogeneity §  Material Aging §  Temperature Range, -30…150 F

Real Stucco

Cracks

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ModelLimita2ons


►  Hysteresis of Moisture Storage Function

0.00 0.20 0.40 0.60 0.80 1.00Relative Humidity (-)

0

50

100

150

200

250

Sorp

tion/

Suct

ion

Isoth

erm

(kg/

m3 )

0.00 0.20 0.40 0.60 0.80 1.00

0

50

100

150

200

250SuctionHygroscopic Regime

Absorption

Desorption

ModelLimita2ons


ExactAirFlowintotheBuildingEnclosure Mostly unknown

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Limita2ons


Example: clay brick with NaCl

Dry-Cup

Wet-Cup

Ref.: Poul Klenz Larsen

Salt Contamination

MoistureStorage increased by salt Vapour diffusion affected by salt

Per

m R

ecip

roca

l

Weathering-roundabout with intermittent heating, cooling and spray-wetting at IBP

Hot box / cold box at ORNL

Solar Radiation Impact

Blackvs.WhiteSurface


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WoodenDeckFlatRoof,WUFI®Pro


§  Location: San Francisco §  Variation: Black vs. White Surface



ASHRAE Handbook of Fundamentals requires moisture below 20 M.-% to avoid wooden decay.

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ASHRAE Standard 160 requires Mold Growth Index (MGI) below 3.0 to avoid visible mold growth

Ques2on:Isaninteriorsprayfoamapplica2ondurablecomparedtothepreviousexis2ngEPSinsula2on?

RetrofitofaHotelinNewOrleansWUFI® Pro

High/LowPermWaterRepellant


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RetrofitofaHotelinNewOrleansWUFI®Pro

#4


#2 #4



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#4, EPS



#4, Open Cell



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DoubleStudWall,WUFI®2DModel

1%RainPenetra2on+CavityVen2la2on

DoubleStudWall,WUFI®2DResults

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Mechanically attached Commercial Metal Deck Flat Roof

Condensa2onRiskofCoolRoofs


Climate

Zone 4 – Baltimore, MD Zone 5 – Chicago, IL Zone 6 – Minneapolis, MN Zone 7 – Fargo, ND

Solar Surface Absorptivity

α=0.30 (White Surface)

α=0.85 (Dark Surface)

Indoor Moisture Supply

ASHRAE 160, Low EN-15026, Normal EN-15026, High ASHRAE 160, High

Air Tightness

Q50=0.27 [l/s,m2] – no perforations

Q50=0.56 [l/s,m2] – little leaky

Q50=1.0 [l/s,m2] – average leaky

Q50=2.0 [l/s,m2] – totally leaky

→ Combination: 128 WUFI Simulations!

CoolRoofs:Varia2onScenario


11/17/17


CoolRoofs:WUFIResults


Indicators for the reliability of the roof construction at given conditions. safe roof construction, gray indicates Black Surface risky construction White Surface expected failure

Not Leaky Little Leaky Avg. Leaky Very Leaky

CoolRoofs:FinalEvalua2onofResults


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Mech.ahachedRoof,Sensi2vityAnalysis


Step1: Measurement of Material Properties for Polyiso, facers separately Coverboard TPO



11/17/17


Polyisofoamcore Facers

Highdensitypolyisocoverboard

Cellulosiccoverboard

TPOmembrane

Bulkdensity ORNL ORNL ORNL ORNL Manufacturer

Porosity est est est est est

Specificheatcapacity est est est est est

Thermalconductivity Manufacturer est Manufacturer Manufacturer est

Watervaporpermeability Manufacturer Manufacturer Manufacturer Manufacturer Manufacturer

Moisturestoragefunction ORNL ORNL ORNL ORNL est

Waterabsorptioncoefficient ORNL ORNL ORNL ORNL est

Thermalconductivitydependenceontemperature Manufacturer Manufacturer Manufacturer Manufacturer Manufacturer

Thermalconductivitydependenceonmoisture est est est est est

Measurement Methodology



Initial and boundary conditions

• Horizontal flat roof • White, reflective roof • Metal roof deck – 1

perm • EMC 80 – initial

moisture content •  Interior climate:

ASHRAE 160



11/17/17


Results Mech.ahachedRoof,Sensi2vityAnalysis


Methodology

•  Four systems – Polyiso, TPO, + two coverboards + with two facers

•  Two climates – Miami and Chicago • Properties were varied +/-20% •  Total moisture content maximum in the 3rd year

compared to baseline



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Sensitivity Analysis Results Mech.ahachedRoof,Sensi2vityAnalysis


Important for all Insulations!

(Insulation Thickness)

Ther

mal

Pe

rfor

man

ce

(Insulation Thickness)

Moi

stur

e Pe

rfor

man

ce

Heatvs.Moisture


11/17/17


Hygrothermal material properties are highly non-linear. (unlike thermal material properties)

Heatvs.Moisture


Measurement&Calcula2on


11/17/17


TheTakeAway


❚  Moisture, and Moisture Damage is a Time Demanding and Transient Process

❚  Moisture Sorption depends on the Relative Humidity

Vapor Transport depends on Absolute Air Humidity

Liquid Transport depends on Liquid Water Content

X

❚  Energy Efficiency conceals a higher Risk of Moisture Damage

❚  Modern Hygrothermal Tools helps for a Modern Enclosure Design

HygrothermalBuildingPerformanceAssessmentinthe21stCentury

Mo2va2on,Basics,ExamplesManfredKehrer


mo2vaon, basics, examples manfred kehrer · wje powerpoint presentaon template 4 mo2vaon the sweden...

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