Measuring the characteristics of thermal insulation · PDF fileMeasuring the characteristics...

Measuring the characteristics of thermal insulation materials

Thermal insulation materials and

applications

1

Mineral fibres

© Claude-A. Roulet, Apples, 2015 2

• Fibres made out of melted glass, ceramic or rock, manufactured by centrifugation spinning.

• Fiberglass from recycled glass

• Rock wool from artificial lava or basalt

• Pure silica and aluminosilicates for high temperatures

• Coated with a resin or needled to make mats and plates

Examples of mineral fibres


Properties of mineral fibres

• Excellent resistance to fire

• Good thermal insulation

• Sound absorption qualities.

• High durability

• Resistant to rot, mould and vermin

• Permeable to air and water vapour

• Absorb water by immersion but drip and dry easily.


Lightweight glass fibres mat


Dense mineral fibres plates


Ceramic insulation


Organic fibres


• Wool, cotton, cellulose, straw, fibres from hemp plant, rice hulls, coco nut or durian

• Marginal market, growing

• Sensitive to moisture, pests, mould and fire

• Absorbs water

Organic fibres


Cellulose Hemp fibres

Wool

Mineral foams: glass foam


Baking at high temperature a mixture of fine glass powder with a bit of carbon powder.

Good resistance to compression but fragile

Totally tight to water and water vapour

Fireproof, service up to 450°C

Resistant to solvents and acids

Resists to rot, mould and vermin.

Expensive

Foamglass


Vermiculite

• Expanded mica, lamellar structure

• Filler for high temperature uses up to 1400 °C

• Hygroscopic (absorbs moisture),

• Very durable, and resistant to acids and alkalis

• Expensive


Vermiculite

13 © Claude-A. Roulet, Apples, 2015

Perlite

• Perlite is natural expanded lava

• Filler for high temperature uses up to 850 °C

• Non combustible

• Hygroscopic (absorbs moisture), but hydrophobic when mixed with bitumen

• Very durable, and resistant to rot, mould and vermin

• Cheap


Perlite


Autoclaved aerated concrete


(AAC), also known as autoclaved cellular concrete (ACC), autoclaved lightweight concrete (ALC)

Cement mortar with aluminium powder, autoclaved

Poor thermal insulation (0.16 < κ <0.21)

Fair mechanical strength

Lightweight building components, roofs, walls

Absorbs water and is very sensitive to frost when

wet

Autoclaved aerated concrete


Organic foams Expanded polystyrene EPS

General use

Poor resistance to water

Mechanical strength sufficient in most cases

Cheap


Extruded polystyrene XPS

Inverted roofs

Underground, drained insulation

Fair resistance to weather and water

Good mechanical strength

More expensive than EPS

Polystyrene foam resist to mould and rot, but can be destroyed by rodents or insects.

It does not resist to solvents and temperatures exceeding 80 °

Organic foams


Polyurethane

Good mechanical strength

Low κ

No resistance to weather and UV and sunlight

On site spraying or injection possible

Urea-formaldehyde

On site injectable foam

No resistance to water but resists rotting

No mechanical strength

Gives off formaldehyde when hardening

Mousses organiques


Applications of PUR foam


Woody materials


Wood fibre and straw


Cork


• Good mechanical strength

• May rot when wet for long

• Fair resistance to fire

Super-insulating materials


Space


• There is neither convection nor conduction in vacuum

• Only radiation remains

• A reflecting suit ensures a nearly perfect thermal insulation .

The Dewar container


• The vacuum between the double wall suppresses convection and conduction

• Reflecting metallised walls strongly reduce radiation

• Only conduction at the neck remains.

Vacuum insulation


Resists to atmospheric pressure (10 t/m²)

Support

material

Airtight

packing

Getter, er

dessiccant

Avoids air to fill the voids in the support material

Keeps a good vacuum despite degassing

Thermal conductivity and pressure


Vacuum insulation


© Claude-A. Roulet, Apples, 2015 32 www.mtsc.unt.edu/faculty/reidy/materials_synt

http://www.mtsc.unt.edu/faculty/reidy/materials_synthesis_and_processi.htm

Silica nanogel

© Claude-A. Roulet, Apples, 2015 33 http://www.boingboing.net/200602061740.jpg

Nanogel products


Heavy gases


• Thermal conductivity of locked gases decreases with the molecular mass

• Ar, Kr, Xe, Freons, SF6 are used in:

– Incandescent lamps

– Double and triple glass panes

– Some foams (e.g. PUR)

Thin reflecting mats


Fibres Reflecting foil(s) Air gap

Thin reflecting mats


Attention to scammers,

miracles are rare !

Minimum thickness for U 0.40 W/m2K


8 c m

E P S

1 0 c m C e l l u l o s e

7.5 cm

X P S

6 c m P U R

1 c m

Vacuum fibre glas

m i n . 20 c m

Thermal, porosified brick

9 c m Foam glas

© Christoph Sibold, 2007


Caracteristics of

insulating materials

Insula

ting p

ow

er

Density

Fire r

ésis

tance

Wate

r vapour

diffu

sio

n

Resis

tance t

o w

ate

r

Com

pre

ssio

n

str

ength

Tra

ction s

trength

Heat re

sis

tance

Absorp

tion

of

vib

rations

Absorp

tion o

f

aerial nois

e

Cost

at giv

en

insula

tion

Gre

y e

nerg

y

Light mineral wool + - - ++ - - 0 - - - - + ++ $ - -

Dense mineral wool ++ + ++ - - 0 0 - ++ ++ + $ 0

Hemp fiber 0 - - 0 - - - - 0 - - 0 ++ $ - -

Wood fibers 0 ++ 0 - - - - + - - + + ++ $$ -

Wood straw -cement - ++ + - - - - + 0 + 0 + $$ -

Cellulose flakes + - - 0 - - - - - - - 0 ++ $ - -

Cork + ++ + + - + 0 ++ + - $$ - -

Glass foam + + ++ ++ ++ ++ ++ ++ - - - $$$ 0

Cellular concrete - - ++ ++ - - ++ + ++ - - - $$$ 0

PUR ++ - 0 - 0 + + ++ - - - $ ++

EPS + - - + + 0 + + 0 - - - $$$ -

Graphited EPS ++ - - + + 0 + + 0 - - - $ -

XPS ++ 0 + ++ + + ++ 0 - - - $ +

Silica aerogel +++ - - + - - ++ - - - + ++ - - $$$$ +++

Applications


Internal or external thermal insulation? Steady state, cold climate


Heavy

building

fabric

Heat flow

Wat

er v

apo

ur

con

den

sati

on

may

occ

urr

her

e

Heat flow

Heat flow

External Internal Distributed

Internal or external thermal insulation? Steady state, hot, sunny climate


Heat flow

Heat flow

Heat flow


Internal or external thermal insulation? Variable outdoor temperature



External insulation Advantages

increases the time constant;

stabilizes the temperature;

store excess heat or recover stored heat;

suppresses most thermal bridges;

in cold climates, completely suppress the risk of water vapour condensation inside the building element.

Inconveniences application from outside;

increases the time required to change the internal temperature.

In air-conditioned buildings located in warm and humid climate, may increase the risk of water vapour condensation inside the building element


Internal insulation Advantages

application from inside;

decreases the time required to change the internal temperature;

In air-conditioned buildings located in warm and humid climate, decreases the risk of water vapour condensation inside the building element.

Inconveniences thermal bridges

in heated buildings located in cold climate, may increase the risk of water vapour condensation inside the building element;

decreases the time constant of the building;

building structure exposed to external variations


Distributed insulation Advantages

simple construction: a single material is used;

regular distribution of the temperature in the wall;

relatively high internal thermal inertia

no condensation problem if permeable finishing.

Inconveniences limited insulation, or

very thick components.

building structure exposed to external variations


Thermal insulation in the building envelope


Homogeneous walls

– massive wood

– porosified clay brick,

– aerated concrete

– compressed straw

– adobe

Roof decks


Without protection

With protection

Inverted roof

Green roofs


Ventilated walls and roofs


External insulation, protected with tiles or cladding

Ventilation removes moisture

Inté

rieu

r

Exté

rieu

r

Inté

rieu

r

Ext

érie

ur

Deck temperature


Inté

rieu

r

Ext

érie

ur

Floor slabs

External insulation


Interior

Exterior

Interior

Exterior

Internal insulation

Insulation of walls


EIFS

ETHICS

Internal

insulation

INdoors

Double

wall

Outd

oors

Lightweight

panel

External Insulation and Finishing Systems (EIFS or ETICS)


Fixation

Insulation

Cement

Mesh

Finishing

EIFS-ETHICS


External insulation

• No thermal bridge

• High thermal innertia

• Good protection of the structure

• No internal condensation.

• Use only proven systems

• DIY is dangerous

• Poor shock resistance.

Advantages Cautions

Transparent insulation


• Solar radiation heats the wall behind the insulation layer.

• Most heat goes inside

• The wall becomes a solar collector

• For cold climates only!

Rayonnement

Heat gains

Pertes

Abso

rbin

g c

oating


Applications

Material

Hom

ogeneous

walls

Com

mon f

lat ro

of

Invert

ed r

oof

Ventila

ted

insula

tion

Betw

een w

alls

Inje

cte

d

Flo

ors

Pre

fabricate

d

panels

EIF

S

Fire p

rote

ction

Acoustic

absorp

tion

Isola

tion

to s

hock

nois

e

Light mineral fibre

Dense mineral fibre

Organic fibres

Wood

Wood fibres

Cellulose fibres

Cork

Glass foam

Aerated concrete

PUR, PIR

PS expanded

PS extruded

Urea Formaldehyde


Optimal thickness

Optimal

thickness


Effects on comfort Thermal inertia

Outdoors

Indoors

Heat storage

Damping of temperature

variations

Practical effects: cold climate

• Paramount for thermal comfort

• Reduces heating cost

• Internal mass allows using free solar gains through windows

• Heating cost may be reduced by a factor 4.


Practical effects: hot climates A necessary complement to solar protection

BEEP guidelines: 50-60% reduction in cooling energy by:

• Use of light colours

• Fixed and movable external window shades

• U-values of walls < 0.5 W/m²K

• Double glazing

• Optimise natural ventilation and

• Airtight envelope

• Over-deck insulation


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