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Last edited 19 Apr 2018
Types of insulation
Thermal insulation materials have a low thermal conductivity which serves to limit the flow of heat energy between one side of the insulation and the other. In the build environment thermal insulation is typically used to reduce the passage of heat between the inside of a building and the outside.
For more information see: Insulation.
There are many different types of insulation, which vary in terms of colour, surface finish texture, core composition and performance. Very broadly however, they tend to be open cell or closed cell.
|Open cell insulation||Closed cell insulation|
Open cell insulation allows the passage of air through air pockets, but the route is so complex that effectively, no air will pass from one side to the other, and so heat transfer by convection is prevented. Closed cell insulation is formed by bubbles of gas whose thermal conductivity is very low.
Some of the more common types are described below.
 Blanket insulation (also called matting insulation)
This is generally the easiest to install and is commonly used as roof insulation. It typically comes in foil-backed rolls which can be placed between joists or rafters, and may be held in place by timber battens attached to and across the joists or rafters.
It is usually made of mineral or glass wool but can also be made from plastic fibres, and natural fibres such as cotton and sheep’s wool. The depth of blanket-style insulation varies depending on the exact composition and the performance required, but it is typically in the range of 100-200 mm.
 Mineral wool
Mineral wool generally refers to fibre materials that are formed by spinning or drawing molten minerals. It can be manufactured in various thicknesses and widths and is often supplied in rolls.
 Sheep’s wool
This type of insulation has the benefit of being 'sustainable', and offers an effective alternative to other synthetic types of insulation. It is increasingly being used between roof beams, under floors and in solid walls. It is often treated to make it more fire and insect resistant.
This type of insulating material consists of glass fibres arranged using a binder into a wool-like texture. Glass wool can be produced in a variety of ways, such as in rolls, slabs, applied in place, or sprayed.
 Foam boards
These are rigid panels of insulation which are cut and fitted in place. Most commonly they are made from polystyrene, polyisocyanurate, and polyurethane, and may be fitted to a depth of around 175 mm. They are used predominantly where there is weight that needs support, i.e. under a floor or in a loft. The benefits of foam boards are that they are durable and can also provide acoustic insulation.
 Radiant barriers
These inhibit heat transfer by thermal radiation. They are capable of being stapled to the underside of rafters. They are more effective in hot climates, where reduced heat gain may allow for smaller air conditioning systems. In cool climates, installing more thermal insulation it is usually more cost effective. The thickness of a radiant barrier is usually between 3-5 mm.
 Blown-in insulation
This involves mineral fibres being blown into a void in the space that needs insulating. Although requiring specialist equipment, it is quick to install and can be effective for spaces with limited access, such as gaps between roof joists or cavity walls. The most common materials that are used include cellulose, fibre glass and mineral rock wool.
 Spray foam insulation
Typically, spray foam is formed of polyurethane and is sprayed as a liquid which gradually expands to up to 100 times its original volume. Once set, it creates an effective thermal and noise insulating layer. Slow-curing foams can be used for cavity walls as they will flow around any obstructions before hardening. As spray foam can produce dangerous fumes and damage the structural integrity of the building if applied incorrectly, professional installation is recommended.
 Structural insulated panels (SIPs)
Structural insulated panels (SIPs) are a form of composite sandwich panel system that incorporates insulation, predominantly used for residential and light commercial construction. They take the form of an insulating core (such as closed-cell polyurethane foam or expanded polystyrene) sandwiched between two structural facings.
The benefits of using SIPs are that they are high-strength, provide good thermal performance and can be fabricated to fit nearly any building design.
For more information, see Structural insulated panels.
Aerogels are synthetic low-density materials with unique physical properties. Due to their high porosity, aerogels exhibit the lowest thermal conductivity of any solid, whilst being transparent to light and solar radiation. Aerogels are often cited as a promising material for translucent insulation applications.
Commercial products for the building sector include:
- Cavity insulation.
- Glazing units and cladding systems containing granular aerogel.
- Translucent and opaque insulation boards, blankets and tensile roof membranes embedded with aerogel particles.
For more information, see Aerogel.
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