Everything you need to know about polyurethane

Current regulations establish the minimum requirements that must be met by buildings, whether it is new construction or renovation. They include some parameters of thermal resistances for the enclosure and, to meet them, we must opt for highly efficient insulating products.

Polyurethane systems in buildings are obtained by the chemical reaction between a diisocyanate and a polyol, which, according to their combination with other substances and / or materials, acquire highly valued and versatile properties such as great resistance, flexibility, rigidity or insulation.

Specifically, due to its highly-efficient insulating properties, it is one of the materials available in the market that offers the best thermal resistance with the minimum increase of thickness. This explains the fact that polyurethane systems are increasingly used in buildings.




Polyurethane characteristics

Optimum thickness according to insulation needs

Knowing the insulation needs of buildings is fundamental to improve their energy efficiency and so that they make a more intelligent use of energy. Therefore, designing their envelope with the optimum insulation thickness is the best strategy to get the most benefits at the lowest cost.

The optimum polyurethane thicknesses can vary according to the geographic area where the building is located, so it will be necessary to check the regulations in this respect in order to use the appropriate values.

Quality control

The quality of sprayed and injected polyurethane is standardized by the European Standards UNE-EN 14315 and UNE-EN 14318, being mandatory throughout the European Union from 1st November 2014. These standards include the specifications of both the systems before installation and the foam once installed.


Sprayed polyurethane foam presents a magnificent adhesion on consistent, clean and dry substrates and, in general, to all the materials used in building. It should not be forgotten that polyurethane foam was discovered during a research on a kind of glue.

The adhesion of other materials to polyurethane can be increased as needed, both physically, by scratching the surface, and chemically, by using a primer.

Thermal conductivity

Polyurethane systems are one of the materials that provide the best thermal insulation with minimal thickness. This characteristic is possible thanks to the low thermal conductivity of polyurethane, since although the differences in the thermal conductivity levels between polystyrene (extruded and expanded), mineral wool and polyurethane systems are theoretically only a few tenths, when applied in the work such decimals can mean a difference of 3-4 cm in thickness to achieve the same energy efficiency.

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Polyurethane application

Polyurethane reception

The aim of the reception control on site is to check that the technical characteristics of the delivered products satisfy the project requirements. This control is carried out at three levels: documentation control, reception control by quality labels, reception control by means of tests.

Besides, since November 2014, it is mandatory to present the CE Marking and the Performance Declaration of polyurethane systems:

  • CE marking: Marking of the product containing the CE logo, the designation code and the essential technical characteristics. Due to the nature of polyurethane systems (liquid components), products are often marked with a label attached to the container.
  • Declaration of Performance (DoP): A signed document containing a product identification code, its intended use and declared performances.

Weather conditions

Rigid polyurethane foam applied in situ by projection has an excellent behaviour against atmospheric agents (water, extreme temperatures, wind...). It is only attacked by prolonged exposure to ultraviolet radiation, contained, for example, in direct sunlight.

Proportions in the mix of components

Each polyurethane system specifically designed for projection or injection in different substrates or molds has a defined proportion, specified in their respective technical sheets.

The conclusion is that the polyurethane base mixture tends to have the same proportion of its two components. If you want to achieve extra performance such as some colour shade, you can add the necessary components to the foam forming process according to the manufacturer's regulations.

Optimum thickness of polyurethane: application conditions

The high insulating capacity of polyurethane is not achieved in construction with any other commonly used insulating material. If polyurethane thicknesses similar to other materials are incorporated, higher thermal resistance and greater energy savings are achieved, which also results in an economic benefit for the end user.

Discontinuity in the application

Discontinuity in the application of polyurethane can seriously result in heating and cooling energy losses. That is why, during the processes of application of this insulating material, it is necessary to respect the order of execution. Otherwise, we could generate serious inconveniences that could have terrible results in the insulating and waterproofing characteristics of this material.

As a general rule, the continuity of the polyurethane foam must not be broken once it has been sprayed, since, in addition to losing insulation properties, the waterproofing effect of the system can be broken and future leaks may appear.


Would you like to learn more about the applications of polyurethane in buildings?:

Polyurethane applications for building - Infographic




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