Post on 28-Mar-2015
Thermal Insulation
Time allowance: 1 hour
Presentation CPD Points: 5 CPD Points
Post presentation online quiz: 5 CPD points
What is Thermal Insulation?
The term thermal insulation refers to materials used to reduce the rate of heat transfer, or the methods and processes used to
reduce heat transfer
Methods of thermal transmittance
Question….
Can anyone name the four methods of heat transfer?
Conduction
Convection
Radiation
Phase change
Mode of heat transfer
Modes Of Heat Transfer
1. Conduction The transfer of heat through a solid object
2. Convection The transfer of heat by conduction in a moving
medium, such as a fluid or gas e.g. water or air
3. Radiation The transfer of heat by electromagnetic radiation
i.e. light waves
4. Phase change The transfer of heat by the potential energy
associated with the heat of phase change, such as boiling, condensation, or freezing
Mode of heat transfer
Conductive Heat Transfer
Thermal conduction
Conduction occurs when heat travels through a medium
Conductive heat transfer is largely reduced by the presence of the air-filled spaces rather than by the material itself
Conductive barriers often have a layer or pockets of air to reduce heat transfer; an obvious example is double glazed windows
Convective Heat Transfer
Convective heat transfer occurs between two objects separated by a moving
interface of liquid or gas
Convective transfer
Convection can be reduced by dividing the convective medium into small compartments (or cells) to prevent large currents from forming
Convective currents, driven by heat energy, occur between the objects
The physical properties of the fluid or gas, and the speed at which the molecules travel, influence the rate of transfer
Radiative Heat Transfer
Most of the energy of the thermal radiation of objects (at room temperature) is in the infrared part of the spectrum
Thermal radiation
Thermal radiation is composed of all wavelengths of light
Any object above Absolute Zero (0 degrees K on the Kelvin scale, or −273.15° Celsius) radiates thermal radiation
Therefore, in thermal insulation the important consideration is the net direction of energy flow
Radiant barriers possess the characteristics of low emissivity, low absorptivity and high reflectivity in the infra-red spectrum
Thermal radiation continued
Therefore, only a small fraction of the radiant energy hitting the surface
is absorbed by such a material; most is being reflected back away and therefore there is little to re-emit
Question….
There are three main factors that compromise the performance of insulation;
what are they?
Moisture
Thermal bridging
Air
Moisture
Damp materials lose most of their insulating properties
Moisture
Similarly, if expanded polystyrene absorbs 5% moisture, it will halve its R value; this is particularly relevant in applications where itis in ‘in ground’ contact.
Therefore, the choice of insulation often dependson the ability to manage moisture and condensation on one side or the other of the insulator
Studies have shown that a 1% increase by volume of water in mineral fibre can increase heat loss by 105%
Thermal Bridging
Comparatively more heat flows through a path of least resistance than flows through an insulated path; this is known as a ‘thermal bridge’
Insulation around a bridge is of little help in preventing heat loss or gain through the bridge due to thermal bridging
Thermal bridging
This is often an issue where insulation is installed between structural members; the affect of this needs to be considered when calculating the ‘system R value’
Where thermal bridges make up 20% of the component area, the system R value for that component of the building may be reduced
by as much as 15%
Further, where the glazed area exceeds 30% of the wall area, the actual system R value may be as much as 40% less than the theoretical system R value
Thermal bridging
System versus Product R-values
Taken from the BRANZ Insulation Guide
Air Flow
Effective insulation relies on “still air”
Air flow
The result of this can be a reduction of the thermal performance of the insulation by up to 50%
A 2mm gap above and below an insulation panel can allow air circulation to occur around the insulation
This circulatory effect will eliminate the still air effect
Insulation Products
Foil Barriers
As discussed previously, aluminium foils are radiant heat insulators
Aluminium foils as radiant barriers
Being metal, foils are good conductors; therefore the effectiveness of an aluminium foil in preventing heat conduction, is minimal
This is particularly true if it abuts another material that also has a high thermal
conductivity, such as a purlins or portals
It also depends on the reflectivity the surface; if oxidization occurs the effectiveness as a radiant barrier is reduced
This is as a result of their low absorptivity and therefore their low emissivity
This has lead to the development of foil products with intermediary air pockets
These products seek to reduce the conductive potential of the foil and therefore increase the system R value
Radiant as combined barriers
When a radiant barrier faces an enclosed air space the combination of the foil
barrier and the still air gap form a conductive insulation barrier
This system has a measurable R-value
The size of the still air gap however largely determines the R value; the foil contributes very little on it’s own
Insulation Blankets
There are two main types of Building Insulation Blankets (B.I.B.s); glasswool, and polyester fibre.
Both glass and polyester blankets have similar thermal performance characteristics; they have a maximum service temperature of 120 degrees C.
At greater thicknesses and densities however, glass tends to perform better thermally
There are some advantages specific to glass over polyester such as the ability to drive mechanical fastenings through the material, particularly in roofing applications
Polyesters conversely tend to be more flexible and are less prone to collapse if they get wet
Insulation Blankets
We have seen a significant increase, in the last 5 years, of the specification of polyester insulation products. This is due to several factors:
Fibre migration within air-conditioning ducting and ventilated plenum spaces. This is despite the WHO removing the 2B (carcinogenic) classification and declaring it safe in October 2002
A perception that polyester insulation is greener than glass wool but…
Glass wool in fact contains around 80% recycled material
And uses 6,600 tonnes of waste window glass annually
Insulation Blankets
Polyester insulation, like glass wool, is a available in sheets and blanket form
Polyester is manufactured from a non–irritant, and non-combustible PET fibre
The recycled content of polyester insulation is increasing in particular via the use of old milk bottles
Efforts are also being made to reduce the embodied energy
However currently the raw materials for polyester insulation are shipped offshore, processed, and then shipped back to New
Zealand for manufacture into insulation
Currently, low density polyester insulation products contain at least 10% of recycled content, with high density products
containing up to 60%
Insulation Blankets
There is a small price premium for polyester over glass wool
In part due to the use of petroleum based product to manufacture polyester
Both are commonly installed in commercial applications, in conjunction with a foil and breathable vapour barrier, in roofs and walls
Common building practices have tended to compromise system R values
Recent legislative changes have meant a stricter enforcement of installation methods
This has impacted on install times and costs and led to the consideration of less traditional solutions
Insulation Blankets
Insulation Blankets
Traditional installation method
Required installation method
Rockwool Insulation
Rock or stone wool insulation
Rock wool, as the name suggests, is manufactured in a furnace from molten rock(typically basalt) at a temperature of about 1600 °C
Much as glass wool is manufactured, the molten rock is spun on high speed spinning wheels
It is a process similar to that used to make candyfloss
The final product is a mass of fine, intertwined fibres; an organic binder is added, often oil, to reduce dusting
Rockwool has a melting point of over 1000 degrees C, making it particularly suitable for fire protection
Question….
Rock or stone wool insulation
Metamorphic stones are good conductor of heat; why then are they used for insulation?
Though the individual fibres conduct heat very well, when pressed into rolls and sheets their ability to partition air makes them excellent heat insulators.
Their high density (between 40 and 120kg/m3) also makes them useful as an acoustic absorbers
Polystyrene Insulation
There are two types of polystyrene insulation:
Expanded or EPS polystyrene (density from 15 to 24kg/m3)
Extruded or XPS polystyrene (density 30kg and above)
Expanded polystyrene is an open cell product; it’s thermal performance is severely compromised when exposed to water and water vapour
Fact 2. Cell Structure Both foams are made using polystyrene monomer. This is the extent of their 'similarity' and the differences are self-evident upon close examination.
STYROFOAM* Extruded Closed Structure Fully closed cells. Water taken up only by direct absorption through polystyrene cell walls - very slow, if at all.
EPS (Expanded Polystyrene) Open Structure Part open, part closed cells. Interstitial voids allow water uptake. Size of voids can cause capillary action and water retention.
Fact 2. Cell Structure Both foams are made using polystyrene monomer. This is the extent of their 'similarity' and the differences are self-evident upon close examination.
STYROFOAM* Extruded Closed Structure Fully closed cells. Water taken up only by direct absorption through polystyrene cell walls - very slow, if at all.
EPS (Expanded Polystyrene) Open Structure Part open, part closed cells. Interstitial voids allow water uptake. Size of voids can cause capillary action and water retention.
Polystyrene Insulation
Extruded Polystyrene is a closed cell product which has minimal absorption characteristics
The thermal performance of extruded polystyrene is around 25% better than that of expanded polystyrene
Many extruded polystyrenes are blown with HCFC’s
These will be largely banned world wide by 2015
Some manufacturers, such as BASF, have therefore moved to CO2 blown manufacture of their expanded polystyrenes
The net result is an entrapment of an ozone depleting substance, rather than a release of it
With a CO2 blowing agent, rather than an HCFC however, there is a thermal performance loss of around 15%
This is due to the conductivity of the gases trapped within the cells and beads
Polystyrene Insulation
High Performance Insulation
High Performance Insulators
Legislative requirements and consumer demand has led to a significant increase
in legislated minimum R values
Key drivers for consumers are both a desire for ever larger glazed areas, and also the desire for more energy efficiency in their buildings
The desire for higher insulation values in walls and ceilings has always had to be
balanced against the impact on the building envelope; on the wall and ceiling thickness’ and the cost
High Performance Insulators
This has led to the development of high performance insulating materials such as Polyurethane (PUR), Polyisocyanurate (PIR) and Phenolic foams
These low density, rigid foam products deliver significantly higher thermal resistivity, for thickness, than more traditional insulants
Further, their closed cell structure means they do not provide a pathway for the ingress of moisture vapour into the insulating material, which significantly
reduces it’s thermal efficiency
Convective transfer - due to the fine closed cell structure of phenolic insulation products, heat transfer through convection is insignificant and can be ignored
High Performance Insulators
The performance of phenolic product can be explained by considering the four factors, which contribute to heat transfer:
Solid conduction – this factor is low in the phenolic cellular structure as the ‘solid content’ typically accounts for about 3-4% of the total volume ofthe low density insulation
Gaseous conduction - the blowing agents used in the creation of the
phenolic foam cellular structure, have very low thermal
conductivity compared to other gases and to air
Radiative transfer - due to their small cellular structure, phenolic foam has a comparatively low radiative heat transfer; radiative heat transfer increases with increasing cell diameter
All blown insulating products undergo changes in cell gas composition over time. This results in changes to their thermal conductivity
Many products, like Kingspan Kooltherm K10, are faced with gas-impermeable materials such as aluminium foil. These facings significantly reduce thermal conductivity aging caused bymigration of air into the insulation
Rigid phenolic insulation also out-performs all other types of rigid insulation for
fire performance. Alternatives such as polystyrene and polyurethanes are becoming less and less popular because of their flammability
Rigid phenolic insulation manufacturers subject their products to regulated testing. Quoted R values take into account aging and also include safety increments to ensure that products deliver better than specified performance over their life
European rigid phenolic insulation is CFC/HCFC-free and has zero ODP
High Performance Insulators
Insulation K values
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
Rockwool Glass wool Polyester ExpandedPolystyrene
ExtrudedPolystyrene
Polyurethane Phenolic
K Value comparisons
U or K Value comparisons
Question….
I mentioned that Phenolic sheets have a solid content of 3-4%; glass wool is similarly only as little as 5% solid. Why do phenolics perform so much better thermally?
Closed cell structure
The very small size of the individual cells largely prevent radiative heat transfer
The gas contained within the cells is a poor thermal conductor
What role does the foil face play in the long term effectiveness of rigid phenolic insulation product?
It largely prevents the migration of air into the cells
As air is a better thermal conductor than the gas within the cells, it significantly improves the insulation’s long term
thermal performance
Cost versus performance
Thickness to achieve R2.6 versus cost m2
100
165
120
6055
$9.00$16.00
$25.00
$12.00
$25.00
$40.00$30.00
75
140
0
20
40
60
80
100
120
140
160
180
Gla
ss Fib
reB
lan
ket
Exp
an
de
dP
olystyrene
Extru
de
dP
olystyrene
Polye
ster
Rock W
ool
PU
R/P
IR
Phe
nolic
(Ko
olthe
rm)
Material
Th
ickn
ess
(mm
) an
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ost
$/m
2
Thickness Cost/m2
Pipe insulation
Pipe insulation fulfils an important function in maintaining the operational reliability of industrial equipment
Insulation keeps the process running, ensures corrosion protection, reduces noise emissions and increases the energy efficiency of the installation
It should therefore be taken into adequate consideration at an early stage of planning
Pipe insulation is made in three forms:
Open cell insulation
Closed cell rigid pipe sections
Closed cell flexible pipe sections
Open Cell Pipe Insulation
Manufactured as a pipe profile section, as a flexible blanket or as a semi rigid board
Densities vary across manufacturers but generally they are around 30-42 kg/m3
The blanket forms are wrapped around objects that are irregular in shape
Blankets are also used to clad large, flat areas
Blanket-type insulation can be specified to protect against heat loss, impact protection and/or fire
Open Cell Pipe Sections
For temperatures between 20 and 400 degrees C, glass fibre insulation is commonly used
This is often bonded to a foil facing to allow wrapping around tight radius and also to increase it insulative properties
For temperatures above around 400 degrees more specialist, high temperature insulators such as Rockwool and ceramic fibres,
such as Calcium Silicate, in rigid pipe sections and blankets are used
Where low temperatures, chemical attack and or moisture ingress (such as in in-ground applications) are a concern, a closed cell
rigid pipe section, such as FoamGlas, is recommended
Open Cell Pipe Sections
Question….
What are the three primary purposes for insulating pipe work?
1. To prevent heat loss
2. To prevent injury through contact
3. Condensation control
Rigid Closed Cell Insulation
Rigid preformed sections are used primarily on straight pipe runs; to both insulate and protect
They are most commonly specified for their extremely high insulating properties, their impact resistance and their chemicalresistance
One such example is Foamglas pipe insulation
Foamglas is a lightweight, rigid, insulating material composed of millions of completely sealed glass cells; each an insulating space
Closed cell, rigid, preformed pipe sections
The all-glass, closed-cell structure makes it a very effective insulator (its U value is between 0.03 and 0.04)
It also has the capability to perform at operating temperatures from minus 268 to plus 482 degrees C
Foamglas is resistant to water in both liquid and vapour form; it is therefore well suited for use in buried and aggressive environments
It is also non-combustible and cannot absorb combustible liquids or vapours
It is also CFC and HCFC free
Closed cell, rigid, preformed pipe sections
Flexible Closed Cell Insulation
For pipe work which carry fluids at below ambient temperature, closed cell insulation should be used
This is because between 40 and 60 % of the maintenance costs for pipe work is due to corrosion under insulation
The main cause of corrosion is damp insulation
Moisture can penetrate the insulation due to damaged to the cladding and/or through water vapour transmission
Condensation occurs when the surface temperature of the pipe is below the dew point temperature
Or when it falls below the dew point temperature, due to changing operating temperatures
In these cases effective corrosion protection must be applied
Flexible Closed Cell Pipe Insulation
Low-temperature insulation materials should therefore be closed-cell
And have a high resistance to water vapour transmission
This is because the low-temperature insulation must prevent moisture from the ambient air penetrating the insulation material
As will occur with an open cell insulation such as glass wool or rock wool
This is known as institial condensation
Flexible Closed Cell Pipe Insulation
ROI case study
The energy saving potential which can be realized by insulating industrial equipment is immense
Calculations carried out by the Dutch Centre for Technical Insulation (NCTI) showed a refinery with a capacity of 300,000 barrels per day, could achieve annual savings of 66 million Euros by insulating 1,375 km of pipe work
According to the NCTI’s model calculation, the costs for the insulation would be paid off after just 3 months
Further, the CO2 emissions could be reduced by 500,000 tonnes a year
The PVC Nitrol pipe insulating products such as the Armaflex range from Armacell offer a thermal conductivity at l0°C ≤ 0.033 W/m.K
When Armaflex is used for pipe insulation on refrigerated lines, the simultaneous improvement of the thermal conductivity and resistance to water vapour transmission has a particularly positive effect on the long-term performance of the pipe work
Question….
What two properties might limit the use of polyesters in pipe insulation?
Maximum operating temperature (120 degrees)
Open cell structure; condensation issues
At what temperature is glass wool is also not suitable?
Above 450 degrees (such as on boilers and furnaces); rock wools are commonly used
Above 120 degrees high temperature binders are added
What rock is rock wool manufactured from?
Most commonly basalt rock
Solid Construction
Recent changes in the Building Act regarding required minimum system R values have had a significant effect on traditional methods of solid
construction
The increases in minimum R values mean that solid wall construction methodologies that were acceptable in the past may not now comply with current legislation
The key to the acceptability of lower R values insolid construction is linked to the ability to utilize the thermal mass of the wall
The standard requires that the thermal mass is accessible; therefore, if the interior walls are insulated, to achieve the required R value, the thermal mass is no longer accessible
Changes in solid construction legislation
High performance insulators, such as phenolics, can deliver a cost effective and efficient solution; minimizing the installation time and also the lost interior space
Green Building
Buildings and associated communities account for over 40% of the world’s greenhouse gas emissions
Specifying the right insulation will increase the building’s energy efficiency, improve the health and well-being of the occupants and reduces
greenhouse gas emissions
It is a low tech and inexpensive solutionthat will deliver a high economic and environmental payback
Energy consumption in buildings is growing faster than most other areas of use
Insulation alone can cut New Zealand’s greenhouse gas emissions by up to 5%
Green Building
Ballard Library in Seattle
The return on the investment in specifying high quality insulation can be measured in months rather than years
Many of the products offered by Forman have zero ozone depleting potential and most contain no CFC’s, or HCFC’s
Many are sourced from suppliers who have made tangible, independently certified,
commitments to pursue sustainable manufacturing practices
We are have a number of our products, including the Kingspan Kooltherm K10, with enhanced listings on the Green Build Website
We are committed to sustainable solutions and continue to expand this area of our offering
Forman and Green Building
Yale Sculpture Building and Gallery
Discover Centre at South Lake Union
Conclusion
Forman have been specifying, selling, distributing and installing insulation products for almost 95 years; so we know insulation!
The range of products we distribute stretches across all the areas discussed today.
Our product range includes the distribution of:
We are happy to assist and advise on the best product for your application
Any Questions?