Sunday, 4 March 2018

Passive Energy Buildings and Insulation - 5 common materials

smart roof


As we have seen in previous articles, thermal insulation performance is usually based on a combination of two characteristics:
  1. Physical properties of the insulation materials to prevent heat transfer.
  2. Materials with proper pore size that allows air to be entrapped within their pores.
Gases have poor thermal conductivity properties in comparison with liquids and solids. Therefore, they are good insulating substances. If gases are to be entrapped within the mass of the material, heat transfer (through convection) will be prevented.
Heat transfer through convection is limited to small pockets where the density is minimized (high entrapped gas composition). For example, this is observed in the structure of a foam material (gas alveoli or bubbles).

While the majority of insulation in the infrastructures is for thermal purposes, the term also applies to hydro insulation, acoustic insulation, fire insulation, and impact insulation (i.e. vibrations caused by industrial applications). The appropriate material selection will be based on its ability to perform several of these functions at once.

Below are five insulation materials commonly used in recent years:




1) Mineral wool





mineral wool

Thermal Conductivity (λ) : 0,033 W / mK
  • Thermal Resistance at 100mm : 2.70 – 2.85 K⋅m2/W
  • Density : 80 kg / m3
  • Temperature range : -200 ° C to 900 ° C
  • Vapour Permeability : 385-400 μgm / Nh (there are fully waterproofing pieces)
  • Compressive strength : 7,5 to 10,5 kN / m2
  • Non flammable
  • Noise absorption (acoustic insulation)

2) Polyurethane foam





polyurethane foam

Thermal Conductivity (λ) : 0,015 - 0.025 W / mK
  • Thermal Resistance at 50mm : 4.5 K⋅m2/W
  • Density : 30-40 kg / m3
  • Temperature range :  -180 ° C to 110 ° C
  • Vapour Permeability : impermeable
  • Compressive Strength : 350 kN / m2
  • Flammable (there are fire resisting pieces)
  • Noise absorption (acoustic insulation)

3) Expanded Polystyrene (EPS)





EPS

Thermal Conductivity (λ) : 0.034–0.038 W / mK
  • Thermal Resistance at 100mm: 3.52 K⋅m2/W
  • Density : 15-30 kg / m3
  • Temperature Range :  -150 ° C to 80 ° C
  • Vapour permeability : Impermeable
  • Compressive Strength : 15 kN / m2
  • Flammable (flame-retardant additives)
  • Noise absorption (acoustic insulation)

4) Extruded polystyrene (ΧPS)





XPS polystyrene

Thermal Conductivity (λ) : 0.033–0.035 W / mK
  • Thermal Resistance at 100mm: 3 K⋅m2/W
  • Density : 20-40 kg / m3
  • Temperature range :  -150 ° C to 80 ° C
  • Vapour Permeability : impermeable
  • Compression Strength : 15 kN / m2
  • Flammable (flame-retardant additives)
  • Noise absorption (acoustic insulation)

5) Aerogels





Aerogel


Thermal Conductivity (λ) : 0.014 W / mK

    • Thermal Resistance at 50mm: 3.8 K⋅m2/W
    • Density : 150 kg / m3
    • Temperature range :  up to 650 ° C
    • Vapour permeability : impermeable
    • Compressive Strength : 20000 kN / m2
    • Non flammable
    • Noise absorption (acoustic insulation)

These materials are suitable for application during the construction of buildings as well as for the retrofit insulation. Depending on the applied scientific research, each of these materials may be suitably reinforced. Most of them are not used as such, but they are combined with other materials to form the total building envelope insulation. In addition to this, it is important to apply the appropriate technology to maintain or achieve the proper ventilation for the building.

Subject to each specific case, the suitable solution is different. It is not necessary to always use the best material, taking into account the needs of each building in a particular geographical area. Of course, the cost-effectiveness factor is also important.

It is worth noting that for new infrastructures, there are new solutions that combine safety, thermal insulation, waterproofing and acoustic insulation, while they are made up of materials that capture and use solar energy (roofs that produce electricity). A typical example is the smart roof that have begun to be implemented.




For any suggestions about materials that we have omitted or materials that you have already used in your own case, just let us know...

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