Everything you need to know about polyurethane

Current technical building regulations establish the minimum requirements that buildings must met, whether it is new construction or renovation. They include some thermal resistance parameters for the building envelope that force to opt for highly efficient insulating products.

The necessary thicknesses of each material to comply with the minimum insulation will consider the location of the house, thermal bridges, the transmittance of cavities, or other peculiarities of the enclosures.

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

In particular, due to its highly efficient insulating properties, it is one of the materials available on the market that offers the best thermal resistance with the minimum increase in thickness. This means that whatever the application, polyurethane systems are increasingly used in buildings construction.





Polyurethane characteristics

Optimum thickness according to insulation needs

Knowing the insulation needs of the building is essential to improve the energy efficiency of the building and for building to  make smarter use of energy. Therefore, designing their envelope with the optimum insulation thickness is the best strategy to achieve the greatest benefit at the lowest cost.

The optimum thickness of polyurethane may vary depending on the geographic area where the building is located, so it will be necessary to check the technical building regulations 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 has excellent adhesion to consistent, clean and dry substrates and, in general, to all the materials used in building construction. It should not be forgotten that polyurethane foam was discovered in the research on a kind of glue.

The adhesion of other materials to polyurethane can be increased as required either physically, by scratching the surface, or chemically, by using a primer.

Thermal conductivity

Polyurethane systems are one of the materials on the market that provides the best thermal insulation with minimum thickness. This characteristic is possible thanks to the low thermal conductivity of polyurethane, as although the differences in the thermal conductivity levels between polystyrene (extruded and expanded), mineral wool and polyurethane systems are theoretically only a few tenths on paper, in their application on site, these decimals can mean a difference of 3-4 cm in thickness to achieve the same energy efficiency of the envelope.


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Polyurethane application

Reception on site

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

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

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

Climatic conditions

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

Mixing ratios of the components

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

The conclusion is that the base polyurethane mixture tends to have the same proportion of its two components. If extra features such as colour tinting is desired, the necessary components can be added in the  foaming process according to the manufacturer's regulations.

Optimum thickness, application conditions

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

Discontinuity of application

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

As a general rule, the continuity of the polyurethane foam projection should not be broken once it has been sprayed, as, in addition to losing insulation properties, the waterproofing effect of the system may 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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