14/11/2005 | Envelope & Coverings | PAGE 1

MICRO-NANO POROUS MATERIALS

FOR HIGH PERFORMANCE

THERMAL INSULATION

Daniel QUENARD – Hébert SALLEECentre Scientifique et Technique du Bâtiment – CSTB – French Building Research InstituteEnvelope & Coverings Department - Material Physics DivisionTel : 33 4 76 76 25 46 – Email : quenard@cstb.fr

2nd International Symposium onNANOTECHNOLOGY in CONSTRUCTIONBILBA0 – 13-16 nov. 2005

Date | SERVICE OU DEPARTEMENT | PAGE 2

From Energy Wasting …

"Almost half of Europe’s energy is consumed in its 160 million buildings.”

ENERGY END-USE EFFICIENCYBy Andrew WarrenMETERING INTERNATIONAL ISSUE 1 2005

Date | SERVICE OU DEPARTEMENT | PAGE 3

Green Paper on Energy Efficiencyor Doing More with Less

FINAL ENERGY DEMANDEurope 2002 Buildings Industry Transport Total

Residential/Tertiary Unit437.8 306 338.9 1083 Mtep40.4 28.3 31.3 %

France 46 25 29 %

Heating 69 %DHW + cooking 19 %

Electricity 12 %

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… to Energy Saving

Among the different measures (efficient boilers, thermal & PV solar collectors) to reduce energy consumption, for both residential and non-residential buildings,

Improvement of building envelopes is by far the most reliable and most cost-effective way to reduce both energy use and CO2 emissions

Thermal Insulation (roofs, walls, windows)Thermal Insulation (roofs, walls, windows),Airtightness & Solar gains

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Thermal Insulation

Source : http://perso.wanadoo.fr/rbm

Source : http://arcticinuit.free.fr

Date | SERVICE OU DEPARTEMENT | PAGE 6

Insulating Materials

VIPVacuum Insulation Materials

Mineral Wool Core MaterialFumed Silica

Airtight Foil

MW, EPSλ = 35 – 40 mW/mK

VIPλVIP = 5 - 10 mW.mK

Date | SERVICE OU DEPARTEMENT | PAGE 7

Fumed Silica

Production Process in a Flame

SiCl4 + 2 H2 + O2 → SiO2 + 4 HCl

BurnerSiCl4 + 2 H2 + O2 SiO2

SiO2SiO2

SiO2

SiO2

proto- primary aggregates agglomeratesparticles particles

Source : WACKER Ceramic

Date | SERVICE OU DEPARTEMENT | PAGE 8

Wacker HDK® PYROGENIC SILICATAMPED DENSITY

Fumed silica appears as a fluffy white powder characterized by an extremly low tamped density down to ~ 50 kg/m3.

Density of SiO2 : ~ 2200 kg/m3

Primary particles do not exist as individual units outside the flame

Date | SERVICE OU DEPARTEMENT | PAGE 9

Hygrothermal Propertiesof Micro-Nano Porous Silica

Porosity Porosity –– Density Density –– Specific AreaSpecific Area

Pore Size DistributionPore Size Distribution

Water Vapor AdsorptionWater Vapor Adsorption

Thermal Conductivity vs Pressure, Moisture & TemperatureThermal Conductivity vs Pressure, Moisture & Temperature

VIP : Vacuum Insulation PanelVIP : Vacuum Insulation Panel

Date | SERVICE OU DEPARTEMENT | PAGE 10

Density, Porosity & Specific area

MaterialReference

TotalPorosity

(Pyc.)

%

BulkDensity(Pyc.)

kg/m3

ApparentDensity

(EN 1602)

kg/m3

SkeletonDensity(Pyc.)

kg/m3

SpecificArea

(BET)

m2/g

SIL1 93 ± 1 191 ± 4 192 ± 4 2578 213

SIL2 94 ± 1 161 ± 4 162 ± 4 2454 208

MW or EPS : 13 to 40 kg/m3

Date | SERVICE OU DEPARTEMENT | PAGE 11

Thermal Conductivity in Porous Materials

rgsrgse λ+λ=λ+λ+λ=λ +

1 : solid conduction (phonons)2 : gas conduction (molecules)3 : radiation (photons)

( ) sggs 1 λ⋅ε−+λ⋅ε=λ +

ε : porosity > 90 %

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Thermal Conductivityvs Total Pressure & Pore Size

1E-3 0.01 0.1 1 10 100 1000

4

8

12

16

20

24

28

Pressure hPa

Fumed Silica 1 CSTB Fumed Silica 2 CSTB Precipitated Silica CSTB Fumed Silica ZAE PU Foam

The

rmal

con

duct

ivity

10-3

W/m

.K δ

100 µm

0.1 µm

Thermal Probe

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Gas Thermal Conductivityvs Total Pressure & Pore Size

g

0gg

PT.C1⋅δ

+

λ=λ

C : constantλg0 : free air conductionδ : pore size.

1 : Low Pressure Pg

2 : Confinement / Knudsen Effect :pore size δ < lm mean free path - δ ∼ 0,1 µm (air)

source : www.empa.ch

Date | SERVICE OU DEPARTEMENT | PAGE 14

Humid Air

N2 78,08 % O2 20,95 % Ar 0,93 %

CO2 0,03 % Xe, Kr, Ne, He 0,01 %

Dry Air

+ Water Vapor H20

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Water Molecule – Molecular Adsorption

Water Molecule Size

0.3 - 0.4 nm

H

O

H Molecular Adsorption

Capillary Condensation

Date | SERVICE OU DEPARTEMENT | PAGE 16

Capillary CondensationKelvin-Laplace Law

( )( ) ( )RHLn1cosT2

RTMR lpK ⋅β⋅σ⋅⋅⋅ρ−=

0.1 µm99 % RH

0,1 µm

Date | SERVICE OU DEPARTEMENT | PAGE 17

Molecular Adsorption& Capillary Condensation

0.0 0.2 0.4 0.6 0.8 1.00.00

0.05

0.10

0.15

0.20

0.25 Fumed Silica 1 CSTB Fumed Silica 2 CSTB Fumed Silica NRC Fumed Silica ZAE

Wat

er c

onte

nt k

g/kg

Relative humidity

Molecular Adsorption

Capillary Condensation

Water moleculein pores

RH increases

Date | SERVICE OU DEPARTEMENT | PAGE 18

Thermal Conductivity vs Water Content

0 5 10 15 20

20

30

40

50

60

Fumed Silica 1 CSTB Fumed Silica 2 CSTB

The

rmal

Con

duct

ivity

10-3

W/m

.K

Water Content %

Temperature : 23 °CAtmospheric Pressure

u : Water Content

uBeu ⋅+λ=λ

Date | SERVICE OU DEPARTEMENT | PAGE 19

Thermal Conductivity vs Vapor Pressure

0 5 10 15 20 25 30

20

30

40

50

60

Fumed Silica 1 CSTB Fumed Silica 2 CSTB

The

rmal

Con

duct

ivity

10-3

W/m

.K

Vapor Pressure hPa

Temperature : 23 °CAtmospheric Pressure

T=23°C – HR = 70 %Pv = 20 hPa

PV = RH.Pvs(T)

( )PvFeu eD1 ⋅⋅−+λ=λ

Date | SERVICE OU DEPARTEMENT | PAGE 20

Thermal Conductivity vs Total Pressure& Water Content

0.01 0.1 1 10 100 1000

5

10

15

20

25

30

35

40

Fumed Silica 2 CSTB dry 30% RH 54% RH 70% RH 80% RH

The

rmal

Con

duct

ivity

10

-3 W

/m.K

Pressure hPa

RH%

SaturatedVapor

PressurehPa

30 8,4354 15,1770 19,6680 22,47

100 28,08

Salt Solution

SampleProbe

Chamber : T=23 °C

80 %

P - N2, O2 = variablePv - H2O = constant

P - N2, O2 = variablePv - H2O = variable

Date | SERVICE OU DEPARTEMENT | PAGE 21

Thermal Conductivity vs Temperature

280 300 320 340 360 380 400 420 440 460 480 500 5202

3

4

5

6

7

8

Fumed Silica 1 CSTB Fumed Silica 2 CSTB Fumed Silica ZAE Precipitated Silica ZAE Fumed Silica 1 NRC

The

rmal

con

duct

ivity

10

-3 W

/m.K

Temperature K

ET

316 3

rσ⋅=λ

Temperature : 23 °CPressure ~ 10-2 mbar

Extinction Coefficient5000 < E < 12000 m-1

Date | SERVICE OU DEPARTEMENT | PAGE 22

Simplified Model

( ) ( )( )⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

⋅δ⋅+

λ⋅ε+⋅−+λ⋅ε−+⎟

⎟⎠

⎞⎜⎜⎝

⎛ σ⋅=λ ⋅

PTC1

eD11ET

316 0gPF

s

3

ev

Radiation GasLow PressureConfinement

Solid + Water

Date | SERVICE OU DEPARTEMENT | PAGE 23

Conclusion

MicroMicro--Nano Porous Silica are good candidates to make VIPNano Porous Silica are good candidates to make VIP’’ss

The Thermal Conductivity is close to The Thermal Conductivity is close to 5 mW/m.K5 mW/m.K at a presssure at a presssure of 10 hPa (0,01 bar).of 10 hPa (0,01 bar).

Due to their high specific area and the microDue to their high specific area and the micro--nano size of their nano size of their pores, porous silica are very sensitive to moisture. Protection pores, porous silica are very sensitive to moisture. Protection against water molecules penetration are essential.against water molecules penetration are essential.

With an initial pressure of 0,01 hPa, there is a safety margin oWith an initial pressure of 0,01 hPa, there is a safety margin of f 3 order of magnitude 3 order of magnitude …… but durability will strongly depend on but durability will strongly depend on the airtightness of the envelope (foil + welding).the airtightness of the envelope (foil + welding).

Date | SERVICE OU DEPARTEMENT | PAGE 24

Supports & Acknowledgements

The results presented in this paper have been obtained within the framework of 3 projects :> Characteristion of Nanoporous Silica - ADEME-EDF-CSTB> European Project VIP-PSS

> Vacuum Insulation Panel – Product & Service System

> Annexe 39 IEA (International Energy Agency )> HIPTI : High Performance Thermal Insulation

Acknowledgements :> B. Yrieix : EDF - S. Kherrouf : ADEME – Peter Randel : WACKER> H. Sallée - C. Pompéo - FD. Menneteau : CSTB