Insulation materials on the market vary widely and are tailored to meet specific technical needs. Let's examine in detail the most popular products and their ideal applications.
Rigid building insulation boards have gained considerable commercial success owing to factors like their high insulating efficiency, straightforward installation, lightness, and manageability. These boards can be effortlessly tailored to size on-site, transported in bulk because of their light weight, and installed with minimal labor.
The intrinsic characteristics of the various materials XPS, EPS, Polyurethane) used to create these insulating panels make each one suitable for some uses and not for others. some of the fundamental characteristics to be evaluated according to use are: vapour permeability, waterproofness, and mechanical resistance to compression.
These aspects are connected to the product's formulation and the inherent properties of its "cells": materials composed of very closed cells tend to be more impermeable and compression-resistant, whereas others might offer some vapor permeability, making them more suitable for internal insulation.
Manufacturers have begun to develop more versatile materials by creating sandwich materials, which consist of a primary insulation layer and an outer 'skin.' This design compensates for certain inherent deficiencies. For instance, materials may be externally laminated with vapor barriers, reflective layers, or waterproofing films to i.e. prevent moisture damage that could compromise the material structural capabilities or its insulating properties.
Certain materials are "charged" with specific additives to augment their natural properties, such as graphite-charged ones. Graphite particles can absorb and reflect heat, reducing heat transfer through radiation due to their honeycomb molecular structure. This graphite enhancement allows for the use of EPS with a lower density, thus utilizing up to 50% less plastic material, resulting in a lighter and more eco-friendly product compared to traditional EPS.
EPS
EPS is derived from polystyrene through polymerization, a chemical reaction that converts styrene, a monomer, into polystyrene, a polymer composed of multiple repeating simple molecules. EPS is 98 percent air, with the remainder being carbon and hydrogen. During polymerization, a blowing agent and other additives may be incorporated into the polystyrene to enhance its properties. The end product of polymerization, supplied to manufacturers, appears as glassy beads of varying sizes. When these beads are exposed to steam at 90°C, the encapsulated gas expands, inflating the beads by 20-50 times their original volume. This expansion creates a closed-cell structure within, trapping air and endowing polystyrene with its superior thermal insulation qualities.
Insulating performance:
EPS insulation boards boast favorable thermal conductivity values (under 0.050 W/mK) along with high resistance to vapor diffusion. They are impervious to moisture and water, yet allow water vapor permeability, granting them a degree of breathability thanks to their internal structure. Sheets within the density range of 30 to 50 kg/m3 offer the best thermal conductivity. Densities below or above this range result in higher λ values, consequently reducing their insulating effectiveness.
XPS
Extruded polystyrene foam is particularly used in construction as an insulation material for the building envelope. These sheets can be utilized alone or laminated with other materials. The production of extruded polystyrene involves raw materials such as virgin and, more recently, recycled polystyrene granulate, various additives, and a blowing gas, all in varying proportions.
Differing from EPS, which is softer, XPS boasts a denser, more robust, and refined structure. It is often further processed to enhance its surface creating and smooth or textured "skin".
The density and compressive strength of XPS render it an outstanding construction material, especially for thermal insulation. It can support greater weights than sintered expanded polystyrene, making it the preferred choice for insulating buildings that bear special loads.
Insulating performance:
The current thermal conductivity values of XPS are slightly better in general than EPS (generically under 0.040 W/mK), but it is the water vapour diffusion resistance (μ) of XPS which is very low - making it suitable for application in wetter environments. Associated with a high compressive strength these characteristics make it preferable in areas such as inverted roof and foundation insulation or ground floor slabs. The product's inherent waterproofness results from the sintering process, which seals its cells through a combination of high pressure and temperature treatment.
PUR and PIR
Polyurethane stands out as one of the most effective insulating materials, enabling the creation of thin and efficient insulating packaging. PUR and PIR are materials based on the same prime materials, yet they possess distinct characteristics. The term polyurethane is broad, encompassing a variety of formulations and applications that result from the reaction between diisocyanate and a polyol.
Discussing polyurethane insulation, we refer to insulation materials derived from either PUR (polyurethane) or PIR (polyisocyanurate). The closed-cell structure and high crosslinking density afford PUR and PIR excellent heat stability, high compressive strength, and superior insulation properties. The latter noted for its enhanced fire resistance.
Insulating performance:
Generally more expensive than other types of insulation, polyurethane-based insulation is often enhanced by coupling it with hi-tech outer layers.
The thermal conductivity of PU, influenced by its coatings and thickness, ranges from 0.022 W/m-K to 0.028 W/m-K. This positions it as one of the most effective insulating materials on the market. In comparison to other materials, PU insulation requires significantly less thickness to attain an equivalent level of thermal performance.
Environmental sustainability:
Unfortunately, one of the critical issues with this type of insulation is its environmental impact. Firstly because these products are predominantly made from petroleum-derived raw materials with many chemicals added, secondarily due to the high temperature and pressure production processes involved.
Although some companies are attempting to establish a particularly virtuous production cycle by creating environmentally sustainable insulation panels, they remain a minority in the global market.
The problem of disposal at the end of its life is also significant. Unlike rock or glass wool mattresses, when a building reaches the end of its life, the removal of the insulation baords is much more challenging because those are directly bonded to the wall structures. The recovered panels must then be cleaned of any residual glue and masonry particles before recycling.
Typical installations:
The success of rigid insulation panels (EPS, XPS, PU based) largely stems from their versatility in addressing a broad range of insulation applications, especially for large surfaces. Typically, these panels are applied externally to insulate building façades, effectively creating a 'coat' that ensures an optimal thermal break between the interior and exterior. To achieve this, it is crucial to "wrap" any protruding elements of the façade, including balcony slabs, structural elements, and parapets that are solidly connected to the perimeter masonry. This can be a complex task, particularly for buildings with intricate façades and various protruding or recessed elements.
Such solutions are not suitable for historic buildings or when the preservation of a building's external appearance is essential. In these cases insulation panels are frequently utilized from the inside. Also, this approach is adopted when a single apartment owner in a block of flats decides to undertake energy improvement on its own.
Insulation panels are also commonly applied to ceilings to minimize thermal radiation from exposed upper floors, such as roof slabs/rooftops.
Due to their mechanical strength, rigid panels are particularly beneficial for insulating foundation structures. Certain materials, like XPS panels, are more favorable due to their inherent moisture resistance and compression strenght, especially when "charged" with specific additives.
Thermal insulation cladding and moisture:
We have already seend that the capacity of these products to manage moisture is contingent upon the internal configuration of their cellular structure. Generally we can say that they are not breathable materials; at most,they may have the capacity to manage a certain ambient humidity without being damaged.
When used as a part of an exterior insulation finishing system (EIFS) or External thermal insulation composite system (ETICS), the insulating panels are shielded by the plastering/finishing layer from environmental humidity. The wall's thickness acts as a buffer, absorbing internal moisture and releasing it towards the inside once the rooms' air has dried up. This, making it improbable for such humidity to penetrate the external insulating layer. Since the wall does not cool significantly, moisture is less prone to migrate to the outer layers. This mechanism allows the system to operate effectively, despite the insulation board's inherently low breathability.
When it comes to insulation from the inside, the breathability of the insulation material is crucial. Accumulated internal humidity, whether from kitchen steam or room overcrowding, can lead to condensation on wall surfaces or within the insulation, in this case compromising its integrity and/or insulating properties. Completely impermeable walls (extensive tiling) may also cause condensation on furniture surfaces when temperatures fall, even if the relative humidity remains constant.
A viable approach when it comes to a partially insulate a room is to apply a thick layer of plaster based on porous materials and natural lime onto the insulating panel. This layer will enable a limited buffering effect that can absorb some moisture while preventing it from penetrating or directly getting in contact with the insulation panel.
The optimal solution involves utilizing highly porous insulation derived from natural materials, which can mimic the breathability of traditional walls. Such products encompass those made from calcium silicates, a completely recyclable, nature-derived material ensuring superior insulation, zero harmful emissions, and environmental sustainability. Because not af all insulating materials were made equal