Types of insulation for the attic floor of a private house - which one is better to choose?

Insulation of the attic floor is carried out in order to retain heat inside the room and prevent the penetration of cold air from the roof.
There is no universal method of thermal insulation for all types of floors. For concrete slabs and wooden ceilings, insulation technologies differ, as does the choice of the insulation material itself.

How to choose the right insulation, and what points to pay attention to when purchasing a product, later in the article.

Main functions

The attic floor is insulated only so that the cold from the roof does not penetrate inside the room or, conversely, the heat from the heated room does not escape through the ceiling. If the task is to insulate the entire attic and turn it into a living space, then it is necessary to insulate the rafter system in addition to the floor itself. This is the difference between cold and warm insulation.

Reference . The insulation of the ceiling is carried out from the attic side, and not in the room itself, in order to save space. The exception is thin foil material.

In the process of insulating the attic floor, you need to think not only about how warm the room will be, but also how to protect the insulating material itself from rotting as a result of condensation accumulation.

If the material is laid incorrectly and the room is not well ventilated, it can begin to rot within six months, affecting the wooden beams, joists and other wooden elements of the attic. An unpleasant smell of dampness appears, and then the entire pie has to be rebuilt and the damaged beams repaired.

Rules for calculating the thickness of ceiling insulation

In order to accurately calculate the thickness of the insulation, it is necessary to determine the heat transfer resistance coefficient of all ceiling materials. It depends on the heating period degree-day (DHD) indicators, which can be calculated independently using the formula presented below.

Tables and other values ​​for calculation can be found in SP 50.13330.2012 or use the one presented below.

“Values ​​of heat transfer resistance in rooms”

It is not at all necessary to carry out these calculations. It is enough just to use a ready-made table.

“Thermal resistance for major cities of Russia (R)”

Requirements

When choosing a material, it is necessary to pay attention to a number of characteristics that certain materials have. What is suitable for a concrete floor will not be suitable for a beam floor. Therefore, it is necessary to consider:

• resistance to moisture accumulation;

• 
  thermal conductivity;

• dimensions (thickness, weight per 1 m3) of the material;
• fire resistance;
• resistance to decomposition and attack by mice, fungus and mold;
• environmental indicators (toxicity);
• vapor permeability;
• maintaining shape when pressed and during operation;
• simplicity in the installation process (release form).

A combination of insulation materials is also used in practice to compensate for the shortcomings of a particular material. For example, crumbly material can be foamed so as not to install an additional frame to hold it. Or the lack of density of mineral wool is compensated for by polyethylene or polystyrene slabs , which also serve as waterproofing.

Moisture absorption

Insulation materials are initially produced in such a way that they absorb moisture as little as possible or not at all, that is, they have water-repellent properties.

Foam insulation materials that do not have natural components cope best in this regard, especially if their cells are closed, like polystyrene foam. When liquid accumulates, the material immediately loses its basic properties by up to 50%, not to mention the fact that it begins to rot and transfer water to the wooden elements of the roof.

Thermal conductivity

The lower the thermal conductivity indicated on the packaging, the warmer the insulation. The average insulator value hovers around 0.04. Some manufacturers indicate the degree of thermal conductivity in 3 states :

• in dry form;
• at a temperature of 10-25°;
• in rooms of categories A and B (+28° and above).

The price depends on the thickness of the insulation and its properties. A thin product, but with a lower thermal conductivity, is more expensive. However, when insulating the attic floor, the thickness of the material does not matter.

If there is no planned residential area in this room, where every centimeter of space is important, then there is no point in buying thin insulation. You can insulate a floor with 1-3 layers of thick material, saving significant money.

Table of coefficients of thermal conductivity, density and vapor permeability of insulation:

Thickness and weight

For wooden floors, the weight of the insulation is important because it is limited. You must not create too much pressure on the floor beams, so that over time they do not begin to sag. At the same time, a thin layer of insulation will not provide the necessary heat retention properties.

To understand what thickness of a particular insulation will be required for a house, you need to use a special table that takes into account the average temperature of the region, the weight of the insulation per 1 m3 and its thermal conductivity.

For example, the owner decided to use mineral wool to insulate the ceiling; he lives in a zone where the average winter temperature is -20°. For his attic it is necessary to lay at least 7 cm of such material. A slab of mineral wool, meter by meter, 7 cm thick, will weigh 14 kg.

In this table you can see the thickness and weight of mineral wool, polystyrene foam and polyurethane foam:

Resistant to fire and decay

When a fire starts in a house, everything starts to burn, even bricks. The insulating material must be resistant to fire and have self-extinguishing properties in case of short circuits and other factors.

In this case, mineral wool, or rather basalt wool, which begins to smolder only at a temperature of 600°, wins. Polystyrene foam or ecowool, which is essentially cut paper, as well as sawdust take first place in terms of flammability.

Exposure to mold, mice

The fewer natural components in the insulation, the less attractive it is to mold. Synthetic materials win in this regard, mineral materials lose, and natural ones, for example, sawdust and husks, are the most suitable for mice and fungi.

However, if waterproofing is installed correctly so as not to create a warm and humid climate for the reproduction of certain organisms, then such incidents can be avoided.

Toxicity

During combustion and normal operation, the insulation should not emit toxic substances. As you know, in the event of a fire, most people die not from burns, but from carbon monoxide and chemicals that the product releases during the combustion process. For example, synthetic materials are the most toxic not only during combustion, but throughout their entire life .

Plastic-based insulation (polyurethane, polystyrene) during normal operation at normal temperatures emit a number of substances, including benzenes, formaldehyde, toluene, acetophenone and others.

Mineral heat insulators are not much better. Although they consist of 80% natural components (basalt, fiberglass), the substances used to combine them are quite toxic (phenols, formaldehyde, etc.). The most environmentally friendly insulation is flax and sawdust, but they are the most flammable. Therefore, the choice will have to be made by the developer himself, which is less dangerous for him.

Vapor permeability

This indicator is only relevant for a wooden house.
Since wood is fibrous, it allows steam to pass through it, and it needs an outlet. Mineral insulation works well for this task.

Water does not accumulate between the attic floor and freely comes out through the mineral wool, and especially through the glass wool. For concrete floors, high vapor permeability is not so important.

Shape stability during operation

Over time, some insulation tends to shrink by a small fraction of a percent, but this fraction is enough to create an air corridor through which heat will begin to escape from the room. EPP (expanded polystyrene) has the best performance in maintaining shape.

It is also the most durable material from the group of lightweight insulation materials, that is, you can walk on it and it will not bend. Mineral wool has the worst performance in terms of shape retention and strength , but it can be compacted for future use, which cannot be said about other heat insulators.

Easy to install

It is best if the insulation can be laid without the use of special equipment and the creation of additional frames. In this case, all hard, medium-hard, tile insulation or mats are suitable.

And although crumbly materials can be laid on the attic floor without difficulty due to the flat horizontal surface, compacting them manually will be difficult and not always of high quality. For example, ecowool is laid both manually and using a sprayer. In the second case, the work will be of the highest quality, without gaps and cracks, but quite expensive.

Ecowool

As the name suggests, this is a more environmentally friendly material than mineral wool. It is most often used for walls, but is also suitable for ceilings as a healthier alternative. Since this type of cotton insulation consists of small crumbly particles, it is possible to carry out both “dry” and “wet” installation.

The “dry” option is simpler. Essentially, you just need to pour the insulation into the space between the beams. For the “wet” method, cotton wool is mixed with an adhesive base and sprayed under air pressure through a special pneumatic tube.

Ecowool prevents the appearance of mold and mildew. It is difficult to ignite due to fireproof impregnation, but even if it does catch fire, it emits a minimum of harmless smoke. It does not retain moisture. Ecowool does not lose its beneficial properties for many years.

How thick should this type of insulation be on the ceiling?

The size of the ecowool layer is not particularly important, since it is compressed to a minimum thickness of a few millimeters and will not load the attic floor. Thanks to the ability to lay wool in one layer, you can save a lot, but due to these features, there are no specific standards for the ecowool layer, and you will have to calculate the thickness of the insulation yourself.

So, let's consider what the thickness of the insulation for the ceiling of a cold attic should be if it is made of ecowool?

In this case, a 25 cm layer will be enough for full functionality. Since under these conditions the insulation dries out and evaporates over time, the layer should be increased by 25 percent of the total thickness. Over the course of a month, the insulation will slowly harden until it turns into one large monolithic surface.

Types of insulating material for the attic

The most popular insulation materials on the market are those belonging to the group of mineral wool and polyethylene foam. There are also loose insulation materials of different consistencies, from expanded clay gravel to sawdust and husks. Each of them has a number of advantages and disadvantages for covering reinforced concrete and wooden floors.

Mineral wool

There are several varieties of mineral wool, differing in source material, density and release form. Thermal conductivity ranges from 0.03 to 0.04. For attic floors use:

• basalt (stone);
• glass wool;
• ecowool.

There is another type of mineral wool, slag wool . It is the cheapest, but it is not used for residential premises. The remaining types of wool are the most optimal and most in demand when insulating wooden walls, rafter systems, and floors in log houses for its vapor-permeable properties and maximum fire resistance.

Watch a video about insulating an attic with mineral wool:

Polystyrene

There are 2 types of polystyrene as insulation, these are ordinary polystyrene foam, also known as polystyrene foam, and extruded polystyrene foam (penoplex), also known as EPS. The difference between them is as follows. Non-extruded polystyrene foam has a looser structure, glued bubbles that crumble during the cutting process; the insulation can be destroyed by slightly squeezing it in your hand.

Extruded, that is, having undergone additional processing, polystyrene foam has a monolithic structure, it does not collapse in the hands, has higher strength when pressed, and it does not accumulate moisture at all. In terms of thermal conductivity, they are almost the same, the indicator is 0.03.

During the installation process, no additional equipment, special clothing or respirators are required. It is easy to cut with a utility knife, and its shelf life exceeds 50 years . The degree of flammability is from G1 to G4 depending on the manufacturer. In this it is inferior to mineral wool, which practically does not burn.

Reference . When choosing a product, you should pay attention to the PSB-S mark on the packaging, it means that the material has self-extinguishing properties.

Polyurethane foam (PPU)

Belongs to the class of sprayed insulation, which are applied using special equipment. It consists of the interaction of an isocyanate and a polyol. The thermal conductivity of the product is at the level of 0.02-0.03. Does not absorb moisture, begins to melt at a temperature of +140° . In this regard, it loses to other insulation materials. But during installation, no vapor or waterproofing is required, since the material itself has such properties.

It is applied to the attic floor between the bars, the same dimensions as those used for insulation with mineral wool (50x200 mm). The insulator differs in density from 15 to 70 kg/m3.

To insulate floors, use a variant with a density of at least 60 kg/m3. The foam fills all the cracks, leaving no gaps or gaps . Shelf life from 30 years. Polyurethane foam is also used for a warm attic, applying foam between the rafters and the sheathing. The composition has good adhesion, so it fits perfectly on the ceiling without glue or staples.

Foamed polyethylene PPE

This type of insulation is used to insulate floors from the inside, that is, in the room itself. The material is produced in combination with foil, it is called foil foam insulation. Its thickness is from 0.5 to 15 mm, so it does not take up much space, but has sound-insulating, hydro- and vapor-insulating properties.

Vapor permeability is one of the lowest, and heat transfer due to the sewn-in foil is one of the highest. Absolutely does not accumulate moisture, the thermal conductivity coefficient is 0.03-0.04 . The only negative is that it only works if there are heat sources in the room, a fireplace, stove or heater.

Wood sawdust

One of the oldest methods of insulating houses. This method is suitable for thermal insulation of wooden houses. Sawdust was used to insulate walls, floors and ceilings. To create the appropriate mixture you will need:

• cement;
• lime;
• water;
• sawdust;
• flame retardants.

Dilute sawdust/cement/lime in a ratio of 10x1x1, water is added at your discretion as a fastening element. At the end, the mixture is flavored with fire retardants.

Blocks are made from this composition or poured directly between the partitions in the attic. To insulate a private winter house, the layer of sawdust with cement and lime must be at least 30 cm; for a summer house, 25 cm is enough.

Reference . To insulate sawdust floors, there is no need to purchase a vapor barrier. This function is taken over by cement.

A significant disadvantage of this method of insulation is the large amount of time it takes to prepare the blocks and the mixture itself, which must harden for a certain time. In addition, cement blocks are quite heavy, creating a weight on the ceiling , not to mention the flammability of the material itself.

Expanded clay

Expanded clay is extracted from clay and sorted by granule size. Symbols for expanded clay are used according to the diameter of the granules:

• sand (up to 5 mm);
• crushed stone (from 5 to 10 mm);
• gravel (from 5 to 40 mm).

The finest expanded clay is used for screeding concrete floors, mixing it with cement and water. Pour it directly onto a flat floor or ceiling using special equipment, level it and let it dry. Large-fraction expanded clay can be insulated manually, pouring it between the racks of timber.

The thermal conductivity of expanded clay is quite high, from 0.07 to 0.16 , in this it is inferior to many materials. In addition, in combination with cement it is quite heavy, which means it is only suitable for insulating reinforced concrete floors. It takes a long time to dry and requires certain skills to use.

Layers of vapor and waterproofing must be laid under the expanded clay layer, since the material is porous and capable of absorbing moisture. It is quite cheap on the market, which makes it popular.

How else can you insulate?

Mention should be made of other types of insulation, which are less popular, but are also used for thermal insulation of attic floors:

• foam glass (pumice);
• blast furnace slag (fuel, coal, metallurgical);
• jute, flax, hay;
• husks (buckwheat, rice, sunflower).

Natural, bulk materials are considered an old-fashioned method that few people use now. They are cheaper on the market, but their significant disadvantage is the danger of mice in them, as well as a high level of inflammation.

• 
  Blast furnace slag outperforms other insulation materials in terms of strength and frost resistance.
  However, the thermal conductivity is gigantic - 0.2 W/(m°C). Among other things, the insulator is very heavy and can also emit radioactive background.

• Foam glass was previously widely used in the USSR and is still used in Europe.
  Its cost is high, due to the labor-intensive manufacturing process. Among the advantages, it is worth canceling the resistance to fire, decomposition and the effects of fungus and mold. Otherwise, it is a fragile material, heavy, suitable only for reinforced concrete floors.

Folgoizol

Folgoizol, or folgopergamine, is a lightweight and highly elastic material for thermal insulation, which is a base made of dense fiberglass covered with aluminum foil.

To insulate ceilings, it is better to use foil insulation of the highest strength; this will extend its service life for decades. The layers of insulation fit tightly to each other, preventing cold from passing through the seams.

Folgoizol practically does not absorb water, but can withstand temperatures up to +125 °C. Dense material with good thermal conductivity. Taking into account such distinctive features, this insulation is well suited for thermal insulation of baths, steam rooms and saunas.

Before deciding how thick the insulation on a foil insulation ceiling should be, you should know the following:

• It is mainly used for thermal insulation of pipes, and it will not save you from frost. It is often used as additional insulation.
• Suitable for latitudes with mild climates.
• The average thickness of the ceiling insulation in this case can be about 1-2 cm.

Average cost of materials in the Russian Federation

The table shows average prices in the Russian Federation in rubles:

Choosing the best mineral wool for insulating the flow in a private house

Mineral wool is popular as insulation due to its low cost, ease of use and durability. It is important to choose the right type of material and install mineral wool on the ceiling. Otherwise, during the first months of operation it will lose up to 40 percent of its thermal insulation qualities.

1. Pros and cons of mineral wool for ceiling insulation
2. How to choose mineral wool
3. Density
4. Thickness
5. Tools and materials
6. Ceiling preparation
7. DIY installation technology
8. Cost of insulation

The best and most sought after

If we talk about the most popular insulation on the market, then 2/3 of all houses are insulated using mineral wool , both for concrete floors and beams.
It is chosen for its moisture resistance, thickness, fire resistance and elasticity.

At the moment, this is the best option in terms of price and quality. It is easy to install and requires no further maintenance. It is used for both warm and cold attics.

However, foam, polystyrene insulation, although not as malleable in shape, does not require the use of a vapor barrier. They are not picky in installation because they do not crumble and do not get under the skin or into the respiratory tract. But they are more flammable, and this indicator reduces the scores for this material.

Natural insulation materials provide an advantage only from an environmental point of view; otherwise, they burn great and serve as a home for mice and parasites.

Granular insulation creates a truly warm atmosphere, but it is incredibly heavy and some types require the use of expensive equipment.

The best thermal insulators for warm and cold attics are those that are sprayed , filling all cavities, relief and cracks. They do not burn or ignite, do not require vapor or waterproofing, do not decompose over time and are not attractive to rodents and bacteria.

But since spraying work costs several times more than installing tile or matte insulation yourself, foam insulation is still left out.

conclusions

To calculate the thickness of the ceiling insulation as accurately as possible, it is necessary to take into account many more factors that were omitted in this example: humidity, functionality of the ceiling, wall and roof material. Before making your own calculations, be sure to study the current SNiP and the Code of Practice for Thermal Protection of Buildings, since many of the values ​​given in the tables above may change.

You can spend a huge amount of time trying to independently answer the question of what layer of insulation is needed for the ceiling of the house. It will be much easier to use online calculators, which are available on most construction company websites and sites selling building materials.

Now, knowing all the main indicators and formulas, you can easily calculate and choose the thickness of insulation for the ceiling that is most suitable in your particular case. It is better to take into account the calculation results with a reserve in order to protect yourself from abnormal frosts and weather changes. But remember that everything depends primarily on the right choice of insulation.

Classification of insulation by density level

Usually everyone remembers school physics and associates the density of insulation with weight and mass.

The heavier the better, but this does not always follow true, depending on what factors and what operating conditions.

The choice of insulation directly depends on the budget, as paradoxical as it may sound, and of course the load on the structure as a whole or on a specific element.

Based on the density of the material, the following classification is distinguished:

Extra light

These include polystyrene foam (expanded polystyrene), which has a porous structure.
Designed for insulation in the cavities of walls, partitions, and for unloaded elements of the house.

Lungs

These are insulation materials based on mineral wool. They have a low thermal conductivity coefficient. Widely used in the construction of private houses and cottages.

Average

These types usually include foam glass. It is in the form of blocks and slabs, with high thermal insulation and sound insulation properties. It is not widespread in Russia.

Dense or hard

They also contain mineral wool, tightly pressed under high pressure. This type of insulation is used for outdoor work and is resistant to moisture and mechanical stress.