Insulating materials play a major role in comfortable, energy-efficient buildings. Thanks to their heat-insulating effect, they save heating and cooling energy and hence contribute to reducing GHG emissions during operation. In addition, thanks to their sound-insulating effect, they provide the basis for acoustic separation via their density properties. Subsequentially, a wide range of products are available for diverse applications and performance properties.
Depending on raw materials, we classify insulation into two broad groups, distinguishing between the inorganic and organic origin of the product. Further subdivision may also be distinguished depending on the further processing of the raw material. Such subdivisions are referred to as either natural or synthetic, with most commercial products being the latter.
As a result of the base raw material of insulation material and the production method, insulating materials exhibit characteristic properties that, in some cases, are not relevant for other materials. Indeed, while insulating materials cover all requirements, there is no single material that fulfils all requirements perfectly, particularly environmental impact requirements. As such, a direct comparison may not always be possible between one product and the next. Nonetheless, to ensure quality in product and application while complying with relevant building code, insulation products are covered by local and international standards.
Closed-cell insulation includes products such as extruded polystyrene and other chemical foam-boards. In manufacture, blowing agents (gases) are introduced. Similar to open cell products, pockets are formed but are much denser and typically with lower thermal conductivity.
Unlike open-cell products, closed-cell materials do not allow water vapour to pass through the core as they are generally hydrophobic, although some chemical foam insulants may be susceptible to break-down over time by the presence of water or water vapour. As such, they need careful consideration when using within building envelope systems, as they can impact the ability for vapour diffusion and lead to mould risk when incorrectly specified.
The material's thermal efficiency is very high and effective over the insulated area but is significantly reduced by poor workmanship in cutting and jointing. In an effort to improve long-term performance, manufacturers face foam-board products in particular, with a shiny foil layer. This acts to minimise contamination by water vapour by acting as a vapour barrier, while also reflecting radiant energy back into the building. Taping of the foil-faced board using a foil tape can improve vapour control, although it will have little impact upon a poorly constructed joint that is not consistently tight.
Phenolic Foam (PF)
Phenolic foam, produced with phenolic resin and pentane, is a brittle material with excellent thermal insulation properties owing to the high proportion of closed cells preventing the loss of the highly insulative gases.
Unlike mineral wool products, phenolic foams are limited in their application and available from only a limited number of suppliers. Due to its brittleness, it can be time-consuming to cut and fit between studs.
With medium densities (40 kg/m²), they are sometimes limited in application but retain similar thermal conductivity performance to other closed-cell products, between 0.022 – 0.040 W/mK.
Polyurethane Ridge Foam (PUR)
Polyurethane ridge foam products are produced from two primary components, polyalcohol and polyisocyanate. Production techniques vary, with foams having more than 90% closed-calls and typically have very high thermal performance, with low thermal conductivity, between 0.024 – 0.030 W/mK.
With very high compressive strength, up to 500 kPa, foams can operate at medium to high temperatures and are resistant to chemicals and solvents.