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It is worthwhile considering the masonry substrate to be part of the MAPETHERM system, even if from a technical point of view it isn’t. In fact, an external insulation system can be installed on practically any type of substrate, as long as it has been adequately prepared.

The external insulation system is a supported element and, as a result, the substrate (whether it is the masonry itself or render) must guarantee sufficient support; it must be able to withstand its own weight, the action of wind, any other loads and, above all, the thermal-hygrometric stresses acting on it.

It is necessary, therefore, to make sure the substrate is flat so that the external insulation system can be installed using the best performing technique possible. It has been demonstrated that the bonding system is more effective and durable over the years if the adhesive has been applied in a continuous layer.

The design engineer who calculates the dimensions for the system is also responsible for choosing the most suitable type and thickness of insulating panel. These are chosen and calculated by taking into consideration the type of building (new or old), the stratigraphic layout of the walls, the loadbearing system (concrete, bricks, poroton, stone, etc.), the area where the building is located and current norms and regulations (and by also taking into consideration, where required, possible tax relief for upgrading a building’s energy performance).

The insulating panels are chosen according to specific requirements. In fact, it is possible to combine their insulating capacity with other properties, depending on which aspect of the system you wish to favour: soundproofing capacity, maximum reaction to fire, maximum permeability to water vapour, very low water absorption, bio-building criteria, overall cost, simplicity of installation, etc.

There are many types of panels available on the market and they are available in different sizes and materials. It is impossible to say which is the best and they must be selected according to the main aims of each specific project. There is no single type of panel available on the market at the moment which offers all the performance characteristics required, so for each project the most important characteristics must be identified to help choose a panel which most closely meets these requirements.

Only panels with the CE logo and which have been declared as suitable for the intended use by the manufacturer must be used.

The adhesive is the first important interfacing element of the system. It must guarantee that its adhesion properties remain stable over the years, resist high sheer and peel loads and counteract thermal expansion in the insulating panels.

A good bond may only be formed if the characteristics of the adhesive are specified correctly, if only selected raw materials are used, if the manufacturer uses a certified quality production cycle and if the adhesive is used correctly on site with the recommended mixing ratios and the correct application techniques and methods are adopted.

This is the second most important interfacing element of the system and must guarantee that the elements remain bonded to it over the years, it must help counteract tensions in the system caused by temperature variations (expansion and contraction of the insulating panels in particular) and it must give the whole system a high level of mechanical strength.

In fact, it is reinforced render that gives the system its mechanical strength, not the density of the insulating panels, as many people wrongly believe. The mechanical strength of the system must be guaranteed in both its dry and wet state. The chemical composition of the skimming product, therefore, is extremely important, particularly the quality of the binder in the product. The thickness applied is also extremely important, which in some cases may be more than 5 mm.

Glass fibre mesh, generally weighing 140-160 g/m², is embedded in the skim coat to distribute the stresses from the substrate and to increase the system’s resistance to impact loads.

It must be treated with an anti-alkali primer to protect it against the basic pH levels of the skimming product it is embedded in and must be woven in such a way that it distributes loads correctly.

Heavier mesh (300-360 g/m²) is stronger which is why, in certain cases, it is used around the footings of buildings in combination with specific skimming products (e.g. MAPETHERM AR 1 LIGHT or MAPETHERM FLEX RP), which are much stronger than the skimming products normally used for external insulation systems.

An external insulation system must be protected against thermal-hygrometric stresses and the surrounding environment with specific finishing products: they are generally quite thick or are applied using systems to guarantee specific performance characteristics .

A finishing product must have the following characteristics: plastic enough to prevent generating cracks, balanced permeability to water vapour, low water absorption to prevent extracting salts or carbonates from the skimming product and to prevent salts and pollutants from the outside being carried into the system, stable colour (if we consider it is applied on a heat barrier), the capacity to resist aggression from mould and algae and a light colour to protect the system from very high surface temperatures caused by exposure to direct sunlight, which in turn generates additional stresses in the entire system (solar reflectance index of more than 20%).