For external and internal insulation of walls of residential buildings, 2 types of thermal insulation materials are used - polymer (foam, extruded polystyrene foam) and porous fiber (mineral wool, basalt fiber, glass wool). Our task is to determine the better to insulate a house from various building materials - brick, wood, concrete. Consider the popular heaters for exterior walls, floors and roofs, compare their insulation properties and durability.
What characteristics are important when choosing thermal insulation
The choice of insulation for finishing the facades of a private house or apartment depends on 3 main characteristics:
- Real thermal conductivity of insulation. It is designated by the Greek letter λ (lambda), measured in units of W / (m • ° С). The smaller the coefficient λ, the better the thermal insulation properties of the material.
- The ability of a heater to pass water vapor is vapor permeability. It is indicated by the letter μ, the unit of measurement is mg / (m • h • Pa). The higher this indicator, the more vapor penetrates the thickness of the insulation.
- The density of the material is ρ, kg / m³. Thermal conductivity and insulation strength depend on it. For example, more dense basalt fiber in the slabs is used for external wall insulation, and rolled mineral wool is used for roofing.
An important point. The thermal conductivity of building materials in the dry state is significantly less than in real conditions. It is her that sellers love to indicate in order to lure buyers. The correct coefficient λ of various heaters under operating conditions is indicated in the table of Appendix “T” to SNiP 23-02-2003 “Heat Protection of Buildings” (aka SP 50.13330.2012).
Knowing the real indicator of thermal insulation λ, it is easy to calculate the layer thickness by the formula:
- R - normative thermal resistance of thermal insulation, m² • ° C / W;
- δ is the thickness of the insulation material, m
The value of R is regulated by building codes. For example, the walls of a country house in the suburbs should have a heat transfer resistance of R = 3.15 m² • ° C / W. If the cottage is insulated from the outside with stone wool with thermal conductivity λ = 0.06 W / (m • ° C), then the thickness of the lining will be 3.15 x 0.06 = 0.189 m or 190 mm.
But in order to understand what kind of insulation it is better to insulate the house, you still need to deal with the vapor permeability of various insulators, the technology of work depends on it. There are other nuances, for example, "Penoplex" does not let pass pairs at all, therefore it is incompatible with wooden walls. Before choosing thermal insulation, we suggest studying the issue ...
About vapor permeability and dew point
There is a lot of conflicting information on this topic on the Internet. There are heated discussions at construction forums about the terrible dew point, because of which water appears and freezes inside the walls, mushrooms grow, bacteria multiply. Let's try to clarify the situation.
In winter, humidity inside living quarters is greater than outside. This means that the air is more saturated with water vapor, respectively, their partial pressure is higher. What happens at the border of 2 zones with different pressures, separated by the wall of our house:
- Vapors from the zone with high partial pressure (rooms) tend to flow into the second zone with low pressure (street), because the partition is leaky.
- As the thickness of the wall passes from the inside out, the temperature decreases. The cooling air is no longer able to retain a large amount of steam, at some point condensation begins. The very dew point arises - the temperature at which saturation occurs, the excess vapors turn into a liquid state, and precipitate.
- The condensation zone and dew point are constantly moving depending on the difference in external / internal temperature, the vapor content in the air of the room.
- When the walls of the house are properly insulated, only a small part of the moisture condenses, this is a normal process. The dew point falls on the heat-insulating layer, the condensate is successfully eroded due to the vapor permeability of the material.
- If an impenetrable barrier appears on the evaporation path (for example, a plastic film), which coincides with the condensation zone, moisture falls out at the boundary of 2 materials. She has nowhere to weather, the wall is damp. A similar effect is observed in the absence of ventilation - air saturated with steam condenses in a cold wall without any insulating barriers.
Note. It is this process that occurs at the junction of a wooden wall made of timber or logs with extruded polystyrene foam. The first passes moisture well, the second is absolutely impervious to steam. The tree is saturated with water and begins to blacken, rot. The way out is to leave a ventilated air gap between 2 dissimilar materials.
Preliminary conclusion: for the ceilings, floor and exterior walls of the house, you can choose any insulation, most importantly, observe the technology of insulation. Remember, the dew point always occurs in the walls, the problem is the amount of condensate and the way it is brought out. The exception is full external insulation with extruded polystyrene foam, inside which condensation is not possible.
Hence 3 recommendations:
- Insulators that are poorly permeable to moisture are best used externally and not fastened end to end to wood.
- Use polymers for internal thermal insulation, but provide effective supply and exhaust ventilation in rooms to remove humid air.
- Materials with open pores (mineral wool) need to be ventilated with street air, which will remove excess steam and condensate from the thickness of the insulation.
Note that ventilation of the premises is necessary in any case. A good hood will save you problems with wet corners and “crying” windows.
4 varieties of insulation
So, for the thermal insulation of private and multi-apartment buildings, 4 groups of materials are used:
- fibrous with open air pores - mineral and basalt (stone) wool, glass wool;
- polymer - ordinary polystyrene foam (also known as polystyrene foam), extruded polystyrene foam, foam polyethylene products;
- filling - expanded clay, vermiculite, a mixture of clay with sawdust and so on;
- liquid - penoizol, polyurethane foam, ecowool.
Comment. We have listed the most popular types of thermal insulation used in private housing construction. Foam glass, wood concrete, perlite rubble and other materials are much less common.
Recently, there have been many combined building materials consisting of several layers. For example, facade thermal panels, which are increasingly lining the walls of multi-storey buildings. Another example is the so-called warm blocks or SIP panels with an insulating layer inside. But for the production of these products, the above basic heaters are still used. Consider each type of insulation separately.
Pros and cons of fiber materials
By name, it is easy to guess that these heaters consist of fibers bonded with synthetic phenol-formaldehyde resins. Fibrous products pass steam well because they have open pores. We list the types and characteristics of these insulators:
- mineral wool with thermal conductivity of 0.055–0.06 W / (m • ° C), vapor permeability - from 0.37 to 0.69 mg / (m • h • Pa) depending on the density and form of release (plate, roll);
- basalt cotton wool, λ = 0.05–0.053 W / (m • ° С), μ = 0.5–0.53 mg / (m • h • Pa);
- glass wool, λ = 0.043–0.061 W / (m • ° С), μ = 0.41–0.6 mg / (m • h • Pa).
Tip. By themselves, the numbers of thermal conductivity and vapor permeability will say little to the average homeowner.But if you compare them with the performance of other heaters, you can draw unambiguous conclusions.
It is noticeable that the operational characteristics of mineral, stone and glass wool are approximately the same, but the properties are slightly different. All 3 materials are non-combustible, but can withstand different temperatures: mineral wool begins to deteriorate at 350 ° C, basalt fiber - at 600 ... 700 ° C, and fiber glass wool melts at 250 ... 300 degrees.
Thermal insulation is available in 3 forms - rolls, plates and mats (the latter are used to warm process pipelines, not walls of houses). The density of coil insulation is 35 ... 60 kg / m³, plate - 60 ... 200 kg / m³. The advantages of porous fiber materials:
- incombustibility is the main plus of such thermal insulation; basalt cotton wool of corrugated structure is the leader among all heat insulation materials by heat resistance;
- due to the high vapor permeability, fiber insulators are “friends” with any walls - brick, wood, reinforced concrete, are constantly used in frame houses;
- slabs with a density of 80 ... 110 kg / m³ well absorb sound, can act as noise insulation;
- rodents do not eat glass wool and mineral wool in the slab version (mice can make holes in soft cotton wool of low density).
In terms of price and thermal conductivity, mineral wool insulation occupies a middle position between polymers and bulk materials. When insulating the walls of a building, only plates are used outside, rolls are designed for thermal insulation of attics and roofs. It is impossible to sheathe the walls and floors of living rooms from the inside - cotton wool emits harmful dust, and binder resin - carcinogens.
The remaining disadvantages of fiber insulation:
- the open pores of any cotton wool must be protected from the ingress of excess moisture, otherwise it will be saturated with water and lose all its insulating properties;
- at the same time, it is necessary to provide for the removal of moisture from the mineral wool formed as a result of condensation;
- low strength;
- over the years, the wall insulation collapses and slowly slides down if it is not fixed;
- glass wool does not burn, but melts in any fire, in addition emits the smallest particles of glass;
- mineral wool plates are heavier than polymer ones, this will become noticeable if we compare the density of materials.
The first 2 drawbacks are eliminated due to the technology of facade insulation. Wool is always protected from precipitation or moisture by special waterproofing - a diffusion membrane (it lets the vapor out) or with a layer of building adhesive + plaster when the installation is done in a “wet” way.
Properties of foamed polymers
These heaters are made of polystyrene and polyethylene, expanded onto a special technology. For thermal insulation of ceilings, walls and floors, 3 types of polymers are used:
- polystyrene foam (otherwise - polystyrene foam), thermal conductivity - from 0.041 to 0.045 W / (m • ° С), vapor permeability - 0.05 mg / (m • h • Pa);
- expanded polystyrene extruded (often called "Penoplex" by the name of the company), λ = 0.037–0.039 W / (m • ° С), μ = 0.02 mg / (m • h • Pa);
- polyethylene foam, also known as Penofol, λ = 0.042–0.044 W / (m • ° С), μ = 0.02 mg / (m • h • Pa).
Reference. Polyfoam and extruded polystyrene are available in the form of plates, foamed polyethylene in rolls.
As you can see, polymers retain heat much better than mineral wool. It is not difficult to compare: the thermal resistance R of the foam with a thickness of 10 cm will be 0.1 / 0.045 = 2.22 m² • ° C / W, of a similar layer of cotton - 0.1 / 0.06 = 1.67 m² • ° C / W, the difference is noticeable.
We list all the advantages of materials:
- foam insulation is the cheapest option for warming the exterior walls of the house (excluding only clay);
- low weight, the density of expanded polystyrene is 15 ... 35 kg / m³, “Penoplex” - 20 ... 40 kg / m³, polyethylene foam - 30 ... 50 kg / m³;
- polymers are durable, service life is at least 50 years, provided that they will not be exposed to direct sunlight;
- they are not afraid of water, as they absorb moisture slightly;
- emit harmful substances in small quantities, especially when heated;
- rolled polyethylene - a durable and flexible insulator, often equipped with a foil that reflects infrared heat;
- polyfoam and “extruder” with a density of over 25 kg / m³ are quite durable, it breaks with difficulty.
Moisture tightness of polymeric heaters - a stick about 2 ends. With polystyrene plates, you can safely insulate the foundation, basement, basement walls outside. On the other hand, it is impossible to sheathe wooden structures with Penoplex; there is a risk of wood decay. Materials can be used indoors, but it is imperative to provide ventilation that will carry off the fumes.
Now let's talk about the shortcomings:
- Polymers are afraid of high temperature, and polystyrene is simply combustible. Self-extinguishing extruded polystyrene melt when heated to 220 ° C.
- Polystyrene products are instantly destroyed by direct exposure to acetone, solvent or gasoline. An example of manufacturing a liquid foam sealant is described in one of our articles.
- Mice gladly gnaw foam insulation, arrange nests in it. “Penoplex” rodents “love” less, practically do not touch polyethylene.
- Thin foamed polyethylene is not suitable for complete insulation of building envelopes.
Disadvantages of bulk insulation
These materials are rarely used for wall insulation. Previously, they were poured into the void between the supporting structure and the brick cladding, now the air gap is filled with polyurethane foam or foam is inserted during construction.
For insulation of attic floors and floors, 3 types of bulk materials are used:
- Expanded clay with a density of 200 ... 800 kg / m³ with thermal conductivity 0.11 ... 0.21 W / (m • ° C), moisture permeability - 0.21 ... 0.26 mg / (m • h • Pa).
- Vermiculite crushed stone 250 kg / m³, λ = 0.13 W / (m • ° С), μ = 0.26 mg / (m • h • Pa).
- A mixture of clay with sawdust or reeds.
Note. The operational characteristics of the clay mixture are not indicated in SNiP; accordingly, we do not list them. It’s pointless to indicate unverified information from the Internet.
There are only 3 advantages of filling heaters - environmental friendliness, incombustibility and durability. Cons look like this:
- thermal conductivity is too high;
- heavy weight;
- the poured layer is easily blown by the wind (except clay);
- decent cost (when it comes to buying materials).
The last paragraph is confirmed by a simple calculation. We found above that the heat transfer resistance of a 100-mm foam layer is R = 2.22 m² • ° C / W. To achieve the same result using expanded clay, you need to fill a layer with a height of 2.22 x 0.11 = 0.24 m = 240 mm (we use the formula given above).
Note, we took the best thermal conductivity for expanded clay gravel with a density of 200 kg / m³. Imagine how much it costs to buy and bring three times as much heavy insulation as compared to polymer. Plus backfill work.
Next, we want to introduce a good comparative review of various materials on the video. One remark: the presenter is disingenuous, sometimes giving incorrect data, trying to present polymers in a worse light.
About liquid thermal insulation
A feature of these materials is the machine application method. That is, liquid insulation is sprayed onto a wall or roof slope using specialized equipment. There are 3 types of such insulation:
- Polyurethane foam is applied in the form of foam, which expands several times in the air, filling the allotted space.
- Ecowool is sprayed in a similar way, but does not expand, as it is made from cellulose.
- Liquid foam - “Penoizol” - is used to fill air cavities.
Reference. The thermal conductivity of polyurethane thermal insulation is 0.04–0.041 W / (m • ° С), the ability to pass steam is 0.05 mg / (m • h • Pa).The characteristics of ecowool are close to the parameters of mineral wool, and Penoizola are similar to ordinary foam.
Liquid polymers are very durable and effective insulators, in addition, they are perfectly “friends” with wood because they let moisture through (albeit in small quantities). Ecowool does not emit harmful substances, therefore it is used indoors.
The main disadvantage of insulation is the high price due to the machine application method. True, warming is done quite quickly, literally in 1 day. Another 2-3 work shifts will be spent on surface preparation - primer and frame mounting. Outside, the insulating layer is protected by a waterproofing film, then it can be sheathed with an inexpensive finish, for example, siding or lining.
What kind of insulation is better to isolate the house
When choosing a heat-insulating material, the homeowner first of all pays attention to its price and the cost of installation work. According to these 2 criteria, polystyrene definitely wins - it is inexpensive, it retains heat well, is relatively easy to attach to the wall and is not afraid of moisture penetration.
For the application of the remaining materials, we give the following recommendations:
- From the point of view of fire safety and protection against rodents, the best insulation is basalt fiber. Suitable for any walls, but needs protection from moisture and ventilation. Stone wool is more expensive than polystyrene, it is more difficult to install.
- A good way to reduce the cost of the warming process is to use foam polystyrene panels with a finished finish for brick, natural stone or other facing materials to choose from.
- Extruded polystyrene foam and sprayed polyurethane give the best thermal insulation effect. Warming will cost a lot, but the layer will come out thinner. Mice gnaw these materials reluctantly, unlike polystyrene.
- It’s better not to risk it and not insulate the wooden houses with Penoplex, especially from the inside. Under certain conditions, wood can rot at the junction with the insulation. Use fibrous heaters, polyurethane foam, ecowool, in extreme cases - polystyrene.
- Brick and concrete facades can be insulated with any material that is suitable for the price. The foundation and base are insulated with polymers that do not absorb moisture.
- The best option for porous walls made of aerated concrete or foam blocks is mineral wool. Polymeric thermal insulation is also suitable, but the thickness of the layer should be correctly calculated so that the vapor condensation zone is always in the thickness of the insulation. An example of decorating a country house from aerated concrete, see the video below.
- Glass wool is used for insulation of roofs and cold attics. If we are talking about the attic, then the cotton wool inserted between the rafters is carefully sewn from the inside with a vapor barrier film.
- Use foamed polyethylene as an additional thermal insulation or a vapor barrier.
Finally, a few words about how it is better to insulate the wall of an apartment building. Typically, foam or thermopanels with finished cladding are used for this purpose. But if at the meeting of the co-owners of the house you decided to sew up the entire wall, it is unacceptable to use polymer materials, only basalt slabs. In the network you can find quite real cases when, due to the foam, the facade of the building burned out from top to bottom.