How to choose foam for home insulation?

6 min

Insulated walls protect the house much better from the penetration of cold in winter, allowing you to significantly save on heating. But when it comes to the very process of warming, each of us wants to get the most effective result and at the same time save more money. Thermal insulation material such as foam is excellent for these requirements. Consider its main advantages and disadvantages, as well as the nuances of choice.

Pros and cons

choose foam for home insulationThere are much more advantages to foam than disadvantages, but first things first. The first advantage that allows the use of foam as a heater is its excellent thermal insulation properties. In addition, this material is not able to absorb moisture, and therefore a vapor barrier is not needed, and in the future this useful property will allow you not to know the problems with the development of mold and mildew.

Polyfoam is a fairly light material, so work to strengthen the foundation is not required, and it is very simple to work with it. It is a durable material that does not deform over time and does not change its properties. The low price for this type of insulation is a decisive argument for its choice.

But not without its drawbacks. The main one is flammability: the foam easily supports combustion, while releasing caustic toxic smoke. That is why it is better to choose a material impregnated with an antiprene composition for insulating a house, which prevents self-ignition. In addition, rodents often arrange minks in the foam, which is a common reason for rejecting this type of insulation, but if the installation is carried out according to all the rules, then this trouble can be avoided.

What is Styrofoam?

choose foam for home insulationThe material that we used to call polystyrene can be made in different ways, eventually forming a material with different properties and appearance. So, the most popular is polystyrene foam. It can be pressed: household appliances are often packed in this, and the material looks like many small balls, tightly pressed against each other. Such material easily crumbles and breaks, and, naturally, is not suitable for insulation. Pressless foam is much more difficult to crush, the granules in it are very tightly bound to each other, but it is also more difficult in production. But both the foam plastic has one drawback – the presence of pores into which moisture vapor can enter, and subsequently condense and destroy the material. That is why only extruded polystyrene is used for insulation, which is devoid of all these drawbacks and can last about 60 years.

choose foam for home insulationIn addition, there are other types of foam on the market that are not used for insulation, so we will briefly mention them. Polyurethane foams are often used in furniture manufacturing. In fact, this is the most common foam rubber, which turns yellow in the sun, is short-lived, crumbles quickly, is very flammable and releases a lot of toxic substances during combustion.

PVC foam is very similar to extrusion foam, but when it burns, it emits much more toxic substances. Polyethylene foam is familiar to many of us: often fragile things are wrapped in its thin sheets.

Slab size

choose foam for home insulationFoam plates are mainly produced in three standard sizes: 0.5 * 1, 1 * 1 and 2 * 1 m.It should be noted right away that this insulation is easy to cut, so no problems should arise during the installation process. So, it is better to choose the material that is most suitable for the area of ​​the insulated surface. As a rule, to insulate balconies, loggias and apartments in apartment buildings, their choice is made on slabs of 0.5 * 1 m in size: it is most convenient to work with them, they are more economical, and it will be easier to insulate all kinds of complex facade details with such material. But if you need to insulate a private house, the walls of which are distinguished by a regular flat surface, then it makes sense to use slabs of 1 * 1 m in size. The largest material, slabs of 2 * 1 m, are used less often for especially large buildings.

What density is needed?

choose foam for home insulationTo insulate a house, polystyrene of different densities is used, depending on what goals are pursued and what exactly needs to be insulated. So, to insulate walls from the outside, it is better to opt for polystyrene with a density of 25 kg / m³, if it is necessary to insulate the floor, then use slabs denser – 35 kg / m³, the same material is used for arranging the roof. But for wall insulation from the inside, it is better to choose foam with a density of 15 kg / m³.

It is better not to use polystyrene with a density of 15 kg / m³ for insulation of external walls. Of course, this is not prohibited, but its durability, strength and reliability will be questionable, which is easy to check on your own, because you just need to compress the material. As a result, you can get less durable insulation, and in terms of the level of thermal insulation, such foam is inferior to a denser analogue. But it is worth noting that such material can be used to insulate non-capital structures: stalls, small shops, warehouses. Also, foam with a density of 15 kg / m³ can be used to insulate some parts of the facade that are adjacent to the house, but do not require serious insulation: veranda, technical buildings, open balconies.

choose foam for home insulation

Polyfoam with a density of 35 kg / m³ is used extremely rarely for wall insulation: it copes with its tasks perfectly, but has a high price. In some cases, by the way, when thermal insulation properties are especially important, it is more advantageous to use a thinner sheet of denser foam than medium density foam, but double thickness. But in most cases it is the material with a density of 25 kg / m³ that is in the highest demand.


The thickness of the foam is a parameter that should be chosen based on an individual combination of factors: wall thickness, wall material, climatic conditions, etc. That is why it is impossible to say that a 5 cm thick foam layer is suitable for absolutely everyone, although it is this material that is most often used to insulate apartment buildings in the temperate zone.

Everyone will be able to calculate the required thickness of the insulation by himself using the tables below. So let’s say you live in a house whose walls consist of two rows of bricks. The heat transfer resistance will be 0.405 m2 * ° C / W. considering that the thickness of the walls is 54 cm. At the same time, the standard value, for example, for Moscow is 3.16 m2 * 0C / W, the difference is 2.755 m2 * C / W, and this is exactly what needs to be compensated for with a heater, the thermal conductivity of which in our case is 0.031 W / m * ° C. It turns out that the thickness of the insulation will be 0.031 * 2.755 = 0.085m, which is 8.5 cm.

Foam quality

choose foam for home insulationWhen all other parameters are determined, you need to evaluate the required material for quality. First, you need to ask for quality certificates: responsible manufacturers and sellers always supply the goods with the necessary documentation confirming their quality. Secondly, you need to make sure that the goods are stored in proper conditions, and that the necessary markings are present on its packaging, informing about the main properties of this material. Polyfoam should not be stored under the influence of direct sunlight: in this case, it loses some of its operational properties, it may begin to emit an unpleasant odor. It is also important that the material is stored in a well-ventilated area and that the humidity is no more than 60%.

Attention should also be paid to the foam granules. They must be of the same size and evenly spaced throughout the volume. If, in some places, there are voids, and the granules easily fall off, then such a product can hardly be called high-quality. In addition, it will not be superfluous to compare individual sheets of material with each other: they must be absolutely the same in thickness, density, with smooth edges, and snow-white.

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Passionate about DIY for over 10 years and all the new tools, I give you through this blog all my advice, tips, tests in all areas: carpentry, electricity, masonry, gardening, home automation ...


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