Mineral Wool Slab/Batts

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Composition

Predominant component or mineral fibre is mineral wool (90 to 99.8% by weight). Other components include:

  • Phenol formaldehyde resin (often modified with urea or lignosulphonates): 10% nominal
  • Mineral oil: 1% nominal
  • Silane: 0.02% nominal
  • Polydimethylsiloxane (or water repellent base on this): 0.1% nominal

The two most common types of mineral fibres are:

  1. Glass wool: a mineral wool (usually borosilicate glass) with a mean fibre diameter of 4-9 µm.
  2. Rock wool: a mineral wool made from naturally occurring igneous rock (such as basalt or diabase) with a mean fibre diameter of 4-9 µm.
Component Content (% wt)
Glass wool Rock wool
Silica (SiO2) 53-65 45-54
Alumina (Al2O3) 2-5 8-15
Titania (TiO2) < or = 0.2 0.6-3
Ferric Oxide (Fe2O3) < or = 0.35 1.8-12.5
Ferrous Oxide (FeO) < or = 0.35 1.8-12.5
Lime (CaO) 6.5-23.5 8-21
Magnesia (MgO) 2-5 3-14
Manganese Oxide (MnO) 0.05 0.2
Sodium Oxide (Na2O) 9-18 1.6-16
Potasium Oxide (K2O) 0.8-1.7 0.4-1.6
Boric Oxide (B2O3) 2-8 <0.2

Thermal Conductivity

Density and temperature differential affect the thermal conductivity of mineral fibre material: 0.03-0.05 W/ mK

Working Temperature

The performance of mineral wool product is unaffected at temperatures up to 230ºC. At temperature above 670ºC softening of glass may commence. The breakdown process is one of softening rather than combustion; at no stage does any significant toxicity occur.

Fire Properties

  1. The basic mineral wool is non-combustible, and does not add to the fire load of the building.
  2. The products have good thermal insulation properties which slow and reduce heat transfer between surfaces, giving protection to structural elements and preventing fire spread.
  3. The surface of the unfaced product act to resist the spread of flame.
Surface appearance Thickness (mm) NRC*
Perforated 12.70 0.45-0.70
15.88 0.55-0.85
19.05 0.60-0.85
22.23 0.45-0.65
Fissured 12.70 0.50-0.65
15.88 0.55-0.85
19.05 0.50-0.90
Textured, finely perforated or smooth 12.70 0.45-0.70
15.88 0.50-0.80
19.05 0.55-0.85
Lays in panels 12.70 0.55-0.70
15.88 0.45-0.90
19.05 0.25-0.95
25.40 0.65-0.95
38.10 0.75-0.85
76.20 0.75-0.85
85.73 0.70-0.80
Rated as part of fire resistive assemblies, perforated, fissured, textured tile. 15.88 0.50-0.75
19.05 0.60-0.85

* The various methods of installing acoustical material affect the NRC values. When an installation system is selected, a much closer NRC value can be obtained. The range is from 250 to 2000 Hz.