They are used as thermal insulators. Materials made from this kind of insulation house millions of micro-pockets, which have air trapped within them. As air is a bad conductor of heat, it provides the insulating effect. This is the reason why it is advised not to compress such materials.
There are some subtypes: batts and blankets, rigid boards, loose-fill, and spray foam. They are pumped, blown, or manually placed into the insulating area.
Batts and Blankets
There are various types of materials used for this such as -
- Glasswool (fiberglass): This is made from glass fibers by melting the glass material and spinning it into a flexible mat of fine fibers. The main advantage is that they are easy to shape and install. But, care must be taken to avoid compressing them, and they must not be exposed to moisture.
- Rockwool: It is fibrous in nature, made from melted volcanic rock, which is later spun. It is mainly used for thermal insulating, but its excellent sound absorption properties has found use in soundproofing as well. It is more expensive than glasswool.
- Natural wool: This is made from the wool obtained from sheep. Natural wool is fire resistant, but is prone to moth attacks.
- Polyester: This is made of polyester fiber, and is similar to rockwool in terms of properties but sans irritations and no physical or health hazards.
These are most-preferred type used in walls and ceilings to provide thermal insulation.
- Extruded Polyester: Made from rigid boards of closed cell polystyrene, which is not only waterproof but has high compressive strength. It can be used with flame retardants, but it is not fireproof itself and should not be installed in areas prone to catch fire.
- Foil-faced Expanded Polystyrene: These are rigid boards of polyester beads fitted with reflective foils attached on two sides. These are not water-resistant and have lower compressive strength.
This is made by blowing loose fiber or pellets of fiber into wall cavities or attics using specially designed equipment. It is generally more expensive than the batt type. However, as it can fill nooks and crannies, thereby reducing air leakage, it provides better soundproofing than the batt type.
Types of loose-fill -
- Cellulose fiber: Made of waste paper which is pulverized into fine fiber. It is much cheaper to install than other bulk installations.
- Granulated Rockwool: It is a granulated loose-fill form of rockwool, and has similar properties as rockwool except that it requires waterproofing.
- Natural wool is also used for loose-fill insulation.
This type generally contains two-parts liquid with polymer (like polyurethane or modified urethane) along with a foaming agent. This foaming liquid is sprayed into cavities in walls, ceilings, or floors using a nozzle.
The polymer has the property of expanding and as it expands, millions of small air-filled cells occupy every nook and cranny inside the cavity. This should only be applied by a professional with special equipment to properly mix and spray the foam.
This type is mostly made of metal sheets of reflective material like aluminum foil laminate. It can minimize the absorption and emission of heat rays by reflecting the heat radiation that strikes its shiny surface. It is most effective when used in conjunction with a layer of still air.
Some of the insulating materials mentioned can also be used for the purpose of soundproofing. Bulk insulation, especially denser materials like rockwool, have desirable sound absorbing properties.
The soundproofing performance of any insulating product is gauged by an index known as Sound Transmission Class (STC). The higher the STC value, the greater the soundproofing ability will be. Blanket types set up directly under metal roofing also absorb external noise.
It is very important to select the most suitable type for you in order to make your home, office, etc. more comfortable.