Which Material?
Types of insulation
There is a very broad spectrum of insulation materials available
on the market, with an equally broad variance in form, performance,
sustainability, cost-effectiveness and availability. Some of the
key types of insulant and their characteristics are set
out below. Knauf Insulation manufactures four different types
of insulation: glass and stone mineral wool; extruded polystyrene
and extruded polyethylene and offers the best solution for the
appropriate application.
We are not therefore constrained to the approach of ‘one
material fits all’ promoted by manufacturers of only one type of
product. Insulation falls into two basic categories: bulk
insulation and foil insulation.
Bulk Insulation
Bulk insulation resists the transfer of heat, by relying on
pockets of trapped air or gas within its structure and its thermal
resistance is consistent regardless of the direction of heat flow
through it. Bulk insulation includes materials such as glass and
stone mineral wool, cellulose fibre, and rigid plastic insulation
boards. All products have a specific thermal resistance for a given
thickness of material at a given temperature.
Foil Insulation
Reflective foil insulation mainly resists radiant heat flow due
to their high reflectivity and low emissivity (ability to reflect
and re-radiate heat). The thermal resistance of reflective
insulation products varies with the direction of heat flow and the
brightness (emmisivity) of the foil facing. Multi foil insulation
products work in the same manner as reflective foil products whilst
also containing several layers of a metallised component which are
usually separated by a combination of wadding and foam.
Mineral wool
There are two basic types of mineral wool insulation:
1. Glass Mineral Wool
Glass mineral wool is made from sand and recycled glass,
limestone and soda ash. These are the same ingredients that are
used to make familiar glass objects such as window panes or glass
bottles. The glass is spun to form millions of fine fibres. A resin
is used to bind the fibres together to form a mat of material. The
density of the product determines whether the insulation is a
lightweight quilt supplied in rolls, a flexible slab or a rigid
slab, and it’s thermal insulation value.
Characteristics
- Long fibre, giving good tear strength
- Suitable for temperatures up to 230°C
- Non-combustible
- Lightweight
- Available in rolls and slabs
Main uses
- Loft Insulation
- Cavity wall insulation
- Sound insulation (absorption) within partitions and floors
UK Manufacturers
- Knauf Insulation
- Isover
- Superglass
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2. Stone Mineral Wool
Stone mineral wool is made mainly from volcanic rock, typically
basalt and/or dolomite. An increasing proportion is now recycled
material from slag, a waste product from blast furnaces. The
materials are melted and then spun into fine fibres. A resin is
used to bind the fibres together to form a mat of insulation.
Characteristics
- Short fibre - compressive strength
- Suitable for temperatures up to 850°C
- Non-combustible
- Denser than glass mineral wool
- Available in the form of slabs, rolls and mattresses
- High compressive strength
Main uses
- Thermal insulation of flat roofs, rainscreen façades and
external wall insulation
- Fire protection, including smoke and fire barriers
- High temperature applications
- Sound insulation for floors and walls
UK Manufacturers
- Knauf Insulation
- Rockwool
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Foamed plastics
There are four main types of plastic insulation:
- Extruded polystyrene (XPS)
- Extruded polyethylene (XPE)
- Expanded polystyrene (EPS)
- Polyurethane/Polyisocyanurate (PUR or PIR)
1. Extruded Polystyrene (XPS)
Extruded polystyrene (XPS) is made by mixing polystyrene pellets
with various ingredients to liquify them. A blowing agent is then
injected into the mixture, to form gas bubbles. Next, the foaming
liquid is forced through a shaping die. When cooled, it produces a
closed-cell foam that is rigid and moisture resistant.
Characteristics
- Lightweight
- Very rigid
- Excellent water resistance
- Suitable for temperatures up to 75°C
- Typically available in 2.4m x 1.2m or 2.4m x 0.6m sheets
- Can be cut to various component shapes and thicknesses
Main uses
- Ground floor
- Flat roofs
- Heavy duty floor insulation
- Panels and other fabrication applications
Manufacturers
- Knauf Insulation: Polyfoam (Orange)
- Dow Building Solutions: Styrofoam (Blue)
- Cellecta: Isofoam (Light Yellow)
- URSA: Poliglas (Dark Yellow)
- BASF: Styrodur (Green)
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2. Extruded Polyethylene (XPE)
Extruded polyethylene (XPE) is made by mixing polyethylene
pellets and other ingredients, a blowing agent is injected in
liquid form causing a foaming reaction. A conical shaping die is
used to shape and form the XPE, producing a material that quickly
cools into a flexible, closed cell plastic foam.
Characteristics
- Lightweight
- Excellent acoustic properties
- Excellent moisture resistance
- Good compression resistance
- Typically sold in roll form
- Available in cut component rolls
Main uses
- Resilient layer in acoustic floors
- Flexible edge strip in screeded floors
- Packaging
Manufacturers
- Knauf Insulation: Floorfoam
- Dow Chemicals: Ethafoam
- Springvale: Geficell
- Cellecta: Yelofon
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3. Expanded Polystyrene (EPS)
Expanded polystyrene (EPS) is manufactured from small spherical
beads of styrene which are pre-expanded with Pentane. The beads
then expand to over 40 times their original size when heated by
steam. The expanded beads stick together under heat and pressure
inside a mould and the finished product consists of approximately
98% fresh air. Expanded polystyrene is also known as ‘bead
board’.
Characteristics
- White/grey colour
- Lightweight
- Suitable for temperatures up to 75°C
- Mainly available in 2.4m x 1.2m sheets
Main uses
- General/domestic-floor thermal insulation
- Wall insulation
- Packaging and fabrication
Manufacturers
- Vencel Resil
- Springvale
- Kay Metzeler
- Sundolit
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4. Polyurethane (PUR) and Polyisocyanurate (PIR)
Polyurethane (PUR) is produced by blowing a non CFC
(chlorofluorocarbon) gas (usually Hydro Carbon Pentane) into
urethane resin to produce a free foaming insulant (the gas used
helps to improve the thermal performance of the product, but
gradually escapes into the atmosphere over time). For this reason
(and to stabilise the foam into boards), polyurethane and
polyisocyanurate (PUR) boards are usually faced with aluminium
foil. Polyisocyanurate is similar to polyurethane but usually
contains long strand glass fibres within the PIR foam core which is
formulated to give off less dense smoke in a fire.
Characteristics
- Usually faced with aluminium foil or glass tissue
- Lightweight
- Good insulation performance
- Mainly available in board form, but can also be spray applied
on site in domestic projects
- Suitable for temperatures up to 75°C
- Combustible
- Potential loss of thermal performance if there is a reduction
in the foil facing emissivity
Main uses
- Flat roofs
- Pitched roofs
- Partial fill cavity wall insulation
- Domestic under-floor insulation
- Foamed composite panels
UK Manufacturers
- Celotex
- Kingspan
- Xtratherm
- Ecotherm
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Reflective foils
There are two types of reflective foils:
- Foil faced bubble wrap
- Multi-layered foils
Reflective foils and multi-layered foils are completely
different types of insulation products to mineral wool and rigid
plastic foam boards.
They work mainly by reducing radiant heat transfer, which is
largely dependent on the emmisivity of the aluminium foil facing.
PUR and PIR rigid board insulation products can also claim
additional thermal performance if they are foil faced and the foil
is adjacent to an airspace. In order to deliver their maximum
thermal performance value, one or both sides of the product should
face an unventilated airspace, if this type of product is installed
without the required airspace of at least 20mm width, then the
thermal performance of the product can be significantly
reduced.
1. Foil Faced Bubble Wrap
Standard bubble wrap which is faced with aluminised polyester
film on both sides. At least one side must face an unventilated
cavity in the construction to work effectively.
Characteristics
- Lightweight
- Thin layer material
- Potential loss of thermal performance if there is a reduction
in the emissivity of the foil facing
Main uses
UK Manufacturers
- Thermal Economics
- Yorkshire Building Supplies (YBS)
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2. Multi-layered Foils
These consist of multiple sheets of aluminised polyester
separated by thin sheets of polyethylene foam. To be effective, the
outer faces must face an unventilated cavity in the
construction.
Characteristics
- Lightweight
- Thin layer material
- Unproven as an alternative to traditional insulation
products
Main Uses
Pitched roofs in hot climates, to stop heat build-up
UK Manufacturers
- YBS
- There are several other suppliers of layered foils in the
UK.
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Insulation Comparisons
The table below compares the key properties of the above
insulants. This is for illustrative purposes only for commonly used
applications for each product.
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Customer requirement
|
Glass mineral wool |
Rock mineral wool |
Extruded polystyrene |
Expanded
polystyrene |
PUR and PIR |
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 Thermal performance
|
high
|
medium
|
high
|
high
|
extra high
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 Cost
|
lower |
low |
high |
medium |
high |
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 Sound absorption
|
high |
high |
none |
none |
none |
 Reaction to Fire |
non-combustible |
non-combustible |
non-combustible |
combustible |
combustible |
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 Compressive strength
|
low |
medium
(suitable for some floors)
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high
(suitable for all floors)
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medium
(suitable for some floors)
|
medium
(suitable for some floors)
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 Water resistance
|
high |
high |
very high
|
high
|
high
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 Weight |
very light - medium
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light - heavy
|
medium
|
medium
|
medium
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 Warehousing space requirements
|
very low
(8:1 packaged compression)
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medium
(2.5:1 packaged compression)
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medium
to
high
|
medium
to
high
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medium
to
high
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 Transport
efficiency
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very good
|
good
|
low
|
low
|
medium
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