Thermal Conductivity on Various Materials

Thermal insulation is the reduction of heat transfer (the transfer of thermal energy between objects of differing temperature) between objects in thermal contact. 

• Reducing the amount of energy used from fossil fuels is the most important factor in promoting sustainability.

• Insulation has the greatest potential for reducing CO2 emissions.

• Energy conserved through insulation use far outweighs the energy used in its manufacture. Only when a building achieves a ‘LowHeat’ standard does insulation’s embodied carbon (see below) become significant.

These are kinds of insulation materials :

Wood fibre

Industrially produced wood fibre insulation was introduced around twenty years ago after engineers from the timber producing areas of Europe devised new ways of transforming timber waste from thinnings and factories into insulation boarding.   Rigid (available in: boards, semi-rigid boards)

Thermal conductivity/ λ (lambda)  W / m . K = 0.038

Thermal resistance at 100mm K⋅m2/W = 2.5

Specific Heat Capacity J / (kg . K)= 2100

Density kg / m3 = 160

(Source: Steico)


Cellulose (blown/sprayed)

Cellulose insulation is a material made from recycled newspaper. The paper is shredded and inorganic salts, such as boric acid, are added for resistance to fire, mould, insects and vermin. The insulation is installed either blown or damp-sprayed depending on application.

Thermal conductivity/ λ (lambda)  W / m . K = 0.035 in lofts; 0.038 - 0.040 in walls.

Thermal resistance at 100mm K⋅m2/W = 2.632

Specific Heat Capacity J / (kg . K)= 2020

Density kg / m3 = 27-65

Embodied energy MJ/kg = 0.45

(Source: Warmcel and others)


Wool (available in batts; rolls)

Wool insulation is made from sheep wool fibres that are either mechanically held together or bonded using between 5% and 15% recycled polyester adhesive to form insulating batts and rolls. Sheep are no longer farmed primarily for their wool; however, they need to be clipped annually to protect the health of the animal. The wool used to manufacture insulation is the wool discarded as waste by other industries due to its colour or grade.(19)

Thermal conductivity/ λ (lambda)  W / m . K = 0.038

Thermal resistance at 100mm K⋅m2/W = 2.63

Specific Heat Capacity J / (kg . K)= 1800

Density kg / m3 = 23

Embodied energy MJ/kg = 6

(Source: Thermafleece)


Hemp (available in: batts; rolls)

Hemp fibres are produced from hemp straw of the hemp plant. Most hemp is imported, but an increasing amount of home-grown crops is becoming available.  Hemp grows up to a height of nearly 4 metres within a period of 100-120 days. Because the plants shade the soil, no chemical protection or toxic additives are required for hemp cultivation. The product is composed of, usually, 85% hemp fibre with the balance made up of polyester binding and 3-5% soda added for fire proofing.Thermal conductivity/ λ (lambda)  W / m . K = 0.039 - 0.040

Thermal resistance at 100mm K⋅m2/W = 2.5

Specific Heat Capacity J / (kg . K)= 1800 - 2300

Density kg / m3 = 25 - 38

Thermal diffusivity m2/s  = n/a

Embodied energy MJ/kg = 10

Vapour permeable: Yes

(Source: Thermafleece and Ecological)



Hempcrete (available in: blocks; in-situ)

Hempcrete is a mixture of hemp hurds (shives) and lime (possibly including natural hydraulic lime, sand, pozzolans or cement) used as a material for construction and insulation. Hempcrete is easier to work with than traditional lime mixes and acts as an insulator and moisture regulator. It lacks the brittleness of concrete and consequently does not need expansion joints. Hempcrete walls must be used together with a frame of another material that supports the vertical load in building construction, as hempcrete's density is 15% that of traditional concrete. (19)

Thermal conductivity/ λ (lambda)  W / m.K = 0.06

Thermal resistance at 100mm K⋅m2/W = 1.429

Specific Heat Capacity J / (kg . K)= 1500 - 1700

Density kg / m3 = 275

Thermal diffusivity m2/s  = 1.5 10-7

Vapour permeable: Yes

(Source: Lime Technology)


Cellular glass (available in: boards)

Largely manufactured from recycled glass (e.g. windscreens) and mineral base materials such as sand and without the use of binding agents.(21) The ingredients are melted into molten glass, which is cooled and crushed into a fine powder. The powdered glass is poured into molds and heated (below the melting point) in a "sintering" process that causes the particles to adhere to one another. Next, a small amount of finely ground carbon-black is added and the material is heated in a "cellulation" process. Here, the carbon reacts with oxygen, creating carbon dioxide, which creates the insulating bubbles in the (material). CO2 accounts for more than 99% of the gas in the cellular spaces.(20)

Thermal conductivity/ λ (lambda)  W / m . K = 0.041

Thermal resistance at 100mm K⋅m2/W = n/a

Specific Heat Capacity J / (kg . K)= 1000

Density kg / m3 = 115

Thermal diffusivity m2/s  =  4.2 · 10–7

Vapour permeable: No

(Source: Foamglas (T4 slab))


Straw (available in : bales, prefabricated units)

Straw is an agricultural by-product, the dry stalks of cereal plants, after the grain and chaff have been removed. Straw makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat.

Thermal conductivity/ λ (lambda)  W / m . K = 0.08 (for loadbearing construction)

Thermal resistance at 350mm K⋅m2/W = 4.37 at 350mm

Specific Heat Capacity J / (kg . K)= unavailable

Density kg / m3 =  110 - 130

Embodied energy MJ/kg = 0.91 (source ICE database 2011)

(Source: BRE + FASBA + others )


Glass mineral wool (available in : batts, rolls)

Made from molten glass, usually with 20% to 30% recycled industrial waste and post-consumer content. The material is formed from fibres of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties. The density of the material can be varied through pressure and binder content.Thermal conductivity/ λ (lambda)  W / m . K = 0.035

Thermal resistance at 100mm K⋅m2/W = 2.85

Specific Heat Capacity J / (kg . K)= 1030

Density kg / m3 =  circa 20

Thermal diffusivity m2/s  =  0.0000016

Embodied energy MJ/kg = 26

Vapour permeable: Yes

(Source: Knauf (Earthwool OmniFit Slab) )


Rock mineral wool (available in: boards, batts, rolls)

Rock (Stone) mineral wool is a furnace product of molten rock at a temperature of about 1600 °C, through which a stream of air or steam is blown. More advanced production techniques are based on spinning molten rock in high-speed spinning heads somewhat like the process used to produce candy floss. The final product is a mass of fine, intertwined fibres with a typical diameter of 2 to 6 micrometers. Mineral wool may contain a binder, often a Ter-polymer, and an oil to reduce dusting.(19)Thermal conductivity/ λ (lambda)  W / m . K = 0.032–0.044 (18)

Thermal resistance at 100mm K⋅m2/W = 2.70 – 2.85

Specific Heat Capacity J / (kg . K) = n/a

Density kg / m3 = n/a

Thermal diffusivity m2/s  = n/a

Embodied energy MJ/kg = n/a

Vapour permeable: Yes

(Source: Various)


Icynene H2FoamLite / LD-C-50 (available in: wet spray; poured)

H2FoamLite is a proprietary insulation manufactured by Icynene, a company based in Canada. H2FoamLite is a spray-applied open cell, water blown, low density polyurethane foam. The product is prepared from two liquid components, isocyanate (BaseSeal) and resin (H2FoamLite), and is yellowish in colour. (22)

Thermal conductivity/ λ (lambda)  W / m . K = 0.039

Thermal resistance at 100mm K⋅m2/W = n/a

Specific Heat Capacity J / (kg . K) = n/a

Density kg / m3 =  7.5 - 8.3

Thermal diffusivity m2/s  = n/a

Embodied energy MJ/kg = n/a

Vapour permeable: Yes

(Source: Icynene)


Phenolic foam (available in: boards)

Phenolic foam insulation is made from a resole resin in the presence of an acid catalyst, blowing agents (such as pentane) and surfactants.

Thermal conductivity/ λ (lambda)  W / m . K = 0.020

Thermal resistance at 100mm K⋅m2/W = 5.00

Specific Heat Capacity J / (kg . K) = n/a

Density kg / m3 =  35

(Source: Kingspan (Kooltherm K3 Floorboard )+ others)


Polyisocyanurate/ Polyurethane foam (PIR/PUR)

Polyurethane (PUR and PU) is a polymer composed of organic units joined by carbamate (urethane) links. Polyurethane can be made in a variety of densities and hardnesses by varying the isocyanate, polyol or additives. 

Polyisocyanurate, also referred to as PIR, is a thermoset plastic typically produced as a foam and used as rigid thermal insulation. Its chemistry is similar to polyurethane (PUR) except that the proportion of methylene diphenyl diisocyanate (MDI) is higher and a polyester-derived polyol is used in the reaction instead of a polyether polyol. Catalysts and additives used in PIR formulations also differ from those used in PUR. Prefabricated PIR sandwich panels are

manufactured with corrosion-protected, corrugated steel facings bonded to a core of PIR foam and used extensively as roofing insulation and vertical walls (e.g. for warehousing, factories, office buildings etc.).(19)

Thermal conductivity/ λ (lambda)  W / m . K = 0.023–0.026(18)

Thermal resistance at 100mm K⋅m2/W = 4.50

Specific Heat Capacity J / (kg . K) = n/a

Density kg / m3 =  30 – 40

Embodied energy MJ/kg = 101 (17)

Vapour permeable: No

(Source: TPM Industrial Insulation & others )


Expanded polystyrene (EPS) (available in: boards, loose fill)

Polystyrene is a synthetic aromatic polymer made from the monomer styrene. Polystyrene can be solid or foamed. Expanded polystyrene (EPS) is a rigid and tough, closed-cell foam. It is usually white and made of pre-expanded polystyrene beads. Polystyrene is one of the most widely used plastics, the scale of its production being several billion kilograms per year. 

Polystyrene foams are produced using blowing agents that form bubbles and expand the foam. In expanded polystyrene, these are usually hydrocarbons such as pentane


Although it is a closed-cell foam, both expanded and extruded polystyrene are not entirely waterproof or vaporproof.

Discarded polystyrene does not biodegrade for hundreds of years and is resistant to photolysis.

Thermal conductivity/ λ (lambda)  W / m . K = 0.034–0.038 (18)

Thermal resistance at 100mm K⋅m2/W = 3.52

Specific Heat Capacity J / (kg . K)= 1300

Density kg / m3 =  15 - 30

Embodied energy MJ/kg = 88.60 (16)

Vapour permeable: No

(Source: DOW and others )


Extruded polystyrene (XPS) (available in: boards)

Extruded polystyrene foam (XPS) consists of closed cells, offers improved surface roughness and higher stiffness and reduced thermal conductivity. (19)  It is slightly denser and therefore slightly stronger thatn EPS.

Water vapour diffusion resistance (μ) of XPS is very low -  making it suitable for application in wetter environments.(19) Boards

Thermal conductivity/ λ (lambda)  W / m . K = 0.033–0.035 (18)

Thermal resistance at 100mm K⋅m2/W = 3

Specific Heat Capacity J / (kg . K)= n/a

Density kg / m3 =  20 - 40 

Embodied energy MJ/kg = 88.6 (16)

Vapour permeable: No

(Source: DOW and others )



Aerogel is a synthetic porous ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas. The result is a solid with extremely low density and low thermal conductivity. Nicknames include frozen smoke and solid air, or blue smoke owing to its translucent nature and the way light scatters in the material. It feels like fragile expanded polystyrene to the touch. Aerogels can be made from a variety of chemical compounds.

Aerogels are good thermal insulators because they almost nullify two of the three methods of heat transfer (convection, conduction, and radiation). They are good conductive insulators because they are composed almost entirely of gas, and gases are very poor heat conductors. They are good convective inhibitors because air cannot circulate through the lattice. Aerogels are poor radiative insulators because infrared radiation (which transfers heat) passes through them.

Silica aerogel is the most common type of aerogel. The silica solidifies into three-dimensional, intertwined clusters that comprise only 3% of the volume. Conduction through the solid is therefore very low. The remaining 97% of the volume is composed of air in extremely small nanopores. The air has little room to move, inhibiting both convection and gas-phase conduction. (19)

 Thermal conductivity/ λ (lambda)  W / m . K = 0.014

Thermal resistance at 50mm K⋅m2/W = 3.8 for 50mm

Specific Heat Capacity J / (kg . K)= 1000

Density kg / m3 =  150

Embodied energy MJ/kg = 5.4kgs / CO² per m²

Vapour permeable: Yes

(Source: Spacetherm & Thermoblock )

All of this insulation Material’s Thermal conductivity/Resistivity/Specific Heat Capacity can be measured by our LINSEIS PRODUCTS LINE