We compare insulation for the house – polyurethane foam or polystyrene foam | Which is better

Insulation materials are indispensable for quality insulation of any buildings and premises. The market abounds with many products designed specifically for this purpose. But, nevertheless, the most popular for a long time are polystyrene foam and polyurethane foam. What are their features and what are the differences between them? Our experts tell you.

Structural features and advantages of materials

To have a more comprehensive view of both insulators and form the right conclusions in comparing them with each other, it is worth more detailed acquaintance with the properties of each.



Both heat insulation have a similar “nature” (made from the same raw materials), but the technology of their production is different, and it determines all. Styrofoam is known among ordinary consumers as Styrofoam. It belongs to the group of polymers and is obtained by foaming polystyrene.

Insulation is represented by 2 varieties: foamed and extruded. The latter has a higher density, which greatly improves the thermal insulation properties of the material, and also prolongs its “life.

NOTE. Styrofoam varieties are difficult to distinguish from each other, but it can be done in a practical way. Enough to break off a small piece of the foam board. Foamed in the place of a break will be visible small balls, with extruded – the correct polyhedrons.


  • Not bad thermal conductivity;

  • Ease of installation;

  • A wide variety of sheet thicknesses;

  • Low price.


  • A small service life (about 10 years);

  • Fast moisture absorption;

  • Exposure to ultraviolet light;

  • Deformation during operation.

Extruded polystyrene foamhas a number of other, more qualitative advantages:

  1. Low level of water absorption;

  2. High durability;

  3. Durability

NOTE.Materials based on polystyrene in any case can not be used for internal insulation, as for a short period of time between the insulation and the wall produces condensate, which may lead to rapid destruction of the construction.

Polyurethane foam

Polyurethane foam

In everyday life is better known as “foam”, only in everyday conditions there is its soft variety, and in construction – rigid. The material is characterized by a closed cellular structure and the presence of edges, which greatly simplifies the installation process. And thanks to special components the insulation is fireproof.

Polyurethane foam is produced by manufacturers in the form of plates or foam, applied a special equipment. The second option is actually devoid of the typical disadvantages of installation (in particular, “thermal bridges”): the coating will be solid.

NOTE. Unlike polystyrene, polyurethane foam can be used without a vapor barrier layer, as its water absorption is very low (15 times lower than that of plastic foam).


  • Moisture resistance;

  • Low thermal conductivity;

  • A wide operational temperature range;

  • No deformation in the process of using insulation;

  • Excellent sound insulating properties;

  • Durability (about 30 years);

  • environmental safety.


  • As for the disadvantages, they are rather formal: high price and unstable to ultraviolet radiation.

Comparative Characteristics

Comparative characteristic

Thermal conductivity

One of the key factors influencing the final choice of a particular insulation for the house. Optimal variants have low thermal conductivity, while allowing a reduction in material thickness during installation.

Comparing polystyrene and polyurethane foam, there is a clear superiority of the first: 0,04-0,06 W/m*K against 0,019-0,028 W/m*K. Due to the denser structure of polystyrene foam better retains heat, but it weighs more (although, this criterion is not considered important when choosing the right insulation).


Polystyrene foam is considered quite strong material that was inherent in it during manufacture (its structure is very homogeneous). And the polyurethane foam is a set of molecules bonded together by exposure to high temperatures.

If you compare in terms that the bending resistance of polystyrene foam is 0.4-1 MPa, and polyurethane foam – 0.07-0.2 MPa. Just the mechanical action is often the cause of the destruction of the latter – it simply crumbles. Enough of any bending, shock during installation to damage the insulation.

Polystyrene foam has a significant strength, which makes it suitable for installation on the load-bearing walls: it is not afraid of temperature jumps, deformation, not subject to shrinkage, etc.


Fire resistance or flammability – an important indicator, especially when it comes to insulation of roofs or facilities, houses, made of wood. Both materials under consideration have similar flammability classes: G2 (polyurethane foam) and G3 (polystyrene foam). G2 means that the material has an average flammability rating, G3 – that the material is flammable.

In fact, the high flammability index is the key disadvantage of both insulators. For this reason, manufacturers began to massively add to the product flame retardants – special components that prevent inflammation of insulation. If it is created according to the technology, in case of fire its extinction will be almost instantaneous.


Unfortunately, both polystyrene and polyurethane foam are toxic materials. But only when subjected to high temperatures: they emit poisonous gas. For this reason, both insulation materials are recommended only for external repair and construction work.

By the way, observing the technology of installation and operation in normal conditions, none of the considered materials does not pose any risk to human health and the environment.

Resistance to moisture

Hydrophobicity – one of the key criteria for choosing insulation and it can not be ignored under any circumstances. Resistance to moisture shows how much the material will be able to withstand moisture during operation. The rate of water absorption should be minimal, otherwise it threatens the destruction of insulation, increasing its weight (which will increase the load on the structure), the loss of the main properties – insulation.

Our experts made a simple but illustrative experiment: we immersed sheets of polystyrene and polyurethane foam in water for 24 hours. The first absorbs only 0.2% of the volume of water (a very low figure), the second absorbs about 2%. Such a significant difference is due to the structure of foamed polystyrene: its closed cells practically impermeable to water.

Vapor permeability

The level of water vapor permeability, too, can not be overlooked, because it depends on it, or additional use of a vapor barrier layer. If we talk about polyurethane foam, its vapor permeability is approximately 0.05 units, but the polystyrene foam, it is actually equal to zero. This suggests that the latter option does not pass steam, respectively, do not have to worry about the additional protection (but only if we are talking about “breathable” surfaces).

Noise insulation level

Neither of the options under consideration can be called suitable for use as noise insulation. Since the densities of both materials are close, they will not have much difference in the level of noise absorption. If you need to provide the room or house quality noise insulation, we recommend the use of additional specially designed for these purposes building material.

Shrinkage rate

The tendency to change the original form – “Achilles heel” of many insulating materials, and one of them – polyurethane foam. This negative property is particularly evident when the insulation is heated: with prolonged exposure to warm air, the board will begin to deform. Do not use polyurethane foam for the “warm floor” system, and when insulating the facade should be concerned about the application for finishing walls plaster with the function of protection against ultraviolet.

Styrofoam is characterized by excellent “resistance” to shrinkage: during operation, the material does not change its original shape regardless of the conditions and place of installation.

Features of installation

And to a word about installation. Both of the considered insulation can be installed without professional help: the materials are very easy to use and will not require special skills. For the convenience of working with polystyrene foam, its sides were equipped with side projections, which, when installed, form an integral layer. In addition, they increase the strength of the material and accelerate the process of work.

Polyurethane foam is mounted on a similar technology, but the process is complicated by the absence of the above-described “sides”: when working with it will have to process the joints with adhesive composition or foam.

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