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

Selecting the appropriate insulation type is essential to improving the energy efficiency of your attic floor. Your home can be kept warm in the winter and cool in the summer by insulating the floor of your attic, which will ultimately reduce your energy costs. However, choosing the best type of insulation for your needs can be difficult given the abundance of options.

Every kind of insulation has benefits and drawbacks of its own. Ease of installation, cost, and thermal performance are all important considerations when choosing the right option for your attic. Knowing these things will enable you to choose wisely, taking into account both your insulation needs and financial constraints.

This post will discuss some of the most widely used insulation materials for attic floors, such as spray foam, cellulose, and fiberglass. We’ll examine each type’s features, advantages, and things to think about before deciding. You’ll know more clearly by the end which kind of insulation is ideal for your attic floor.

Type of Insulation	Advantages
Fiberglass	Affordable, easy to install, non-flammable
Mineral Wool	Excellent fire resistance, good sound insulation
Spray Foam	High R-value, fills gaps and cracks, acts as an air barrier
Cellulose	Eco-friendly, good sound insulation, affordable
Rigid Foam	High R-value, moisture resistant, durable

Main functions

The sole purpose of the attic floor’s insulation is to prevent heat from the heated room from escaping through the ceiling or cold from the roof from entering the space. In addition to the floor, the rafter system needs to be insulated if the goal is to completely enclose the attic and convert it into a living area. This is how warm and cold insulation differ from one another.

Reference: To conserve space, ceiling insulation is installed from the attic side rather than within the room. The thin foil material is an exception.

When it comes to attic floor insulation, it’s important to consider not only how warm the space will be but also how to prevent condensation from rotting the insulation material.

Within six months, the material may start to rot if it is not properly laid and the space is not well ventilated. This will affect the attic’s wooden floors, joists, and other wooden components. Then there’s a bad smell like wetness, and you have to rearrange the whole cake and fix any broken beams.

Requirements

There are several qualities that certain materials have that need to be considered when selecting a material. A beam floor is not the right place for anything that works for a concrete floor. As a result, it is important to think about:

• 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).

In actual use, a variety of insulating materials is employed to make up for a material’s shortcomings. For instance, crumbly material can be foamed to avoid the need for an extra frame to support it. Alternatively slabs made of polyethylene or polystyrene, which also serve as waterproofing, make up for the lack of density in mineral wool.

Moisture absorption

Originally, insulation materials are made to either absorb moisture very little or not at all; in other words, they are made to be water-repellent.

The best foam insulation in this regard is that which contains no natural components, such as polystyrene foam, whose cells are closed. Liquid accumulation causes the material to instantly lose up to 50% of its basic qualities. It also causes the material to rot and allows water to seep into the wooden components of the roof.

Thermal conductivity

The insulation is warmer if the packaging indicates a lower thermal conductivity. The insulator value varies on average by approximately 0.04. Three states are indicated by certain manufacturers for the degree of thermal conductivity:

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

The insulation’s qualities and thickness determine its cost. The product costs more even though it is thinner and has a lower heat conductivity. Nevertheless, the material’s thickness is irrelevant when it comes to attic floor insulation.

Purchasing thin insulation is pointless if this room is not intended to be a residential area where every square centimeter matters. With one to three thick layers of material, you can insulate a floor and save a lot of money.

Table showing the insulation’s vapor permeability, density, and thermal conductivity coefficients:

Thickness and weight

The weight of the insulation is significant for wooden floors because it is finite. In order to prevent the beams from sagging over time, avoid applying excessive pressure to their ceilings. However, a thin layer of insulation won’t offer the required capacity to retain heat.

Using a specific table that accounts for the average temperature of the area, the weight of the insulation per square meter, and its thermal conductivity, you can determine the thickness of an insulation that will be needed for a house.

For instance, the owner chose to insulate the floor with mineral wool because he lives in an area where winter temperatures typically drop to -20°. It is necessary to lay at least 7 cm of such material in his attic. A meter by meter, 7 cm thick slab of mineral wool will weigh fourteen kilograms.

The thickness and weight of mineral wool, polystyrene foam, and polyurethane foam are displayed in the following table:

Resistant to fire and decay

Bricks are not exempt from burning when a house fire breaks out. In the event of a short circuit or other occurrence, the insulating material must be self-extinguishing and fire resistant.

The winner in this instance is mineral wool, or more specifically, basalt wool, which smolders at a temperature of only 600°. Sawdust and polystyrene foam, also known as ecowool—basically, cut paper—come in first in terms of flammability.

Exposure to mold, mice

Mold is less drawn to insulation that contains fewer natural components. In this sense, synthetic materials triumph, mineral materials fail, and natural materials—like sawdust and husks—work best for mice and fungi.

However, these kinds of incidents can be prevented if waterproofing is installed correctly so as not to create a warm and humid climate that encourages the reproduction of certain organisms.

Toxicity

Toxic substances shouldn’t be released by the insulation during combustion or regular operation. As you are aware, the majority of fire victims pass away from chemicals and carbon monoxide released by the burning product rather than from burns. For instance, synthetic materials are the most toxic during their whole life, not just when they burn.

When plastic-based insulation (polyurethane, polystyrene) is used normally at room temperature, it releases a variety of chemicals, such as formaldehyde, toluene, acetophenone, and benzenes.

Heat insulators made of minerals are not much better. Despite having 80% natural components (basalt, fiberglass), the materials used to assemble them (phenols, formaldehyde, etc.) are highly toxic. Sawdust and flax make the most flammable insulation, but they are also the most environmentally friendly. Consequently, the developer will have to make the decision for himself, which is less risky for him.

Vapor permeability

This is a sign that applies exclusively to wooden houses.

Because wood is fibrous, steam can permeate it and needs a way out. For this purpose, mineral insulation is effective.

Water escapes freely through the mineral wool, particularly the glass wool, and does not collect between the attic floor. High vapor permeability is not as crucial for concrete floors.

Shape stability during operation

A tiny percentage of insulation tends to shrink over time, but this fraction is sufficient to open up an air passageway that allows heat to start escaping the space. Expanded polystyrene, or EPP, performs the best at keeping its shape.

Among the lightweight insulation materials, it is also the most resilient; you can walk on it without it bending. When it comes to strength and shape retention, mineral wool performs the worst; however, unlike other heat insulators, it can be compacted for later use.

Easy to install

It is ideal if installing the insulation doesn’t require the building of extra frames or the need for specialized equipment. Any hard or medium-hard tile insulation or mats work well in this situation.

Additionally, even though the attic floor’s level horizontal surface makes it easy to lay crumbly materials, manually compacting them will be challenging and the quality won’t always be optimal. For instance, ecowool is sprayed as well as laid by hand. In the second scenario, the work will be of the greatest caliber, flawless and devoid of cracks, but it will cost a lot of money.

Private home insulation selection for the attic floor requires careful consideration of your home’s unique requirements, financial constraints, and climate. With their own advantages, popular choices include rigid foam boards, fiberglass, spray foam, and cellulose. Fiberglass is inexpensive and simple to install, but spray foam provides superior air sealing. Rigid foam boards are incredibly strong and resistant to moisture, while cellulose is environmentally friendly and performs well in terms of heat. You can choose the best insulation for your attic floor by weighing these options in accordance with your priorities.

Types of insulating material for the attic

Mineral wool and polyethylene foam are two of the most widely used insulation materials available today. Additionally, there are loose insulating materials of various densities, such as sawdust, husks, and expanded clay gravel. Each of them has a variety of benefits and drawbacks when it comes to covering wooden and reinforced concrete floors.

Mineral wool

Mineral wool comes in a variety of forms, with variations in density, release form, and source material. The range of thermal conductivity is 0.03 to 0.04. For use on attic floors:

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

Slag wool is a different variety of mineral wool. Although it is the least expensive, residential properties do not use it. Because of their maximum fire resistance and vapor-permeable qualities, the remaining types of wool are the best and most in-demand when it comes to insulating wooden walls, rafter systems, and floors in log houses.

Watch this video to learn how to use mineral wool for attic insulation:

Polystyrene

Polystyrene comes in two varieties for use as insulation: regular polystyrene foam, or polystyrene foam, and extruded polystyrene foam (penoplex), or EPS. What separates them is as follows. With its looser structure and glued bubbles that burst when cutting, non-extruded polystyrene foam is easily destroyed by gently crushing it in your hand.

Polystyrene foam that has been extruded, or processed further, has a monolithic structure, resists crumbling in your hands, is more resilient when pressed, and doesn’t retain any moisture at all. They are nearly identical in terms of thermal conductivity; the indicator is 0.03.

There is no need for respirators, extra equipment, or special attire during installation. Its shelf life is more than 50 years, and it cuts easily with a stationery knife. G1 to G4 is the range of flammability, depending on the manufacturer. It is not as good as mineral wool in this regard, as the latter essentially never burns.

Reference: The PSB-S mark on the packaging indicates that the product has self-extinguishing qualities, so keep an eye out for it when making your selection.

Polyurethane foam (PPU)

Falls under the category of sprayed insulation, which is applied with specialized tools. It is made up of the reaction between polyol and isocyanate. The product’s thermal conductivity is between 0.02-0.03. At +140°, it starts to melt and doesn’t absorb moisture. It falls short of other insulating materials in this regard. However, because the material itself has these qualities, no vapor or waterproofing is needed during installation.

Apply to the attic floor between the bars using the same dimensions (50 x 200 mm) as mineral wool insulation. The density of the insulator varies from 15 to 70 kg/m 3.

Use a variety with a density of at least 60 kg/m 3 when insulating floors. All crevices are filled with foam, leaving no spaces. thirty years’ worth of shelf life. PPU is also used to apply foam between the sheathing and rafters in a warm attic. Without the need for glue or staples, the composition fits flawlessly on the ceiling due to its strong adhesion.

Foamed polyethylene PPE

Floors are insulated with this kind of insulation from the interior, or from within the room. Foil foam insulation is the term for the substance that is created when foil is combined with it. It is thin—between 0.5 and 15 mm—and has vapor, hydro, and sound insulation qualities without taking up much room.

One of the lowest vapor permeability and one of the highest heat transfer rates is a result of the sewn-in foil. It does not retain moisture at all; its thermal conductivity coefficient is 0.03–0.04. The fact that it requires heat sources such as a stove, heater, or fireplace to function is its lone drawback.

Wood sawdust

One of the earliest techniques for home insulation. This technique works well for insulating wooden homes from the heat. Sawdust was employed as an insulator for ceilings, floors, and walls. To make the right mixture, you’ll need:

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

Water is added as a fastening element at your discretion to a mixture of diluted sawdust, cement, and lime in a ratio of 10x1x1. Fire retardants are added to the mixture at the end to flavor it.

This mixture is used to make blocks or it can be poured straight between the attic’s partitions. A layer of sawdust mixed with cement and lime needs to be at least 30 cm thick to insulate a private winter house; 25 cm is sufficient for a summer house.

Reference: A vapor barrier does not need to be purchased in order to insulate sawdust floors. Cement takes over this function.

This insulation method’s main drawback is how long it takes to prepare the blocks and mixture, which needs to harden for a specific amount of time. In addition to their inherent combustibility, cement blocks are heavy and cause a weight on the ceiling.

Expanded clay

Extracted from clay, expanded clay is arranged according to granule size. Symbols for expanded clay are utilized based on the granule diameter:

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

When screeding concrete floors, the best expanded clay is combined with cement and water. Using specialized equipment, pour it directly onto a level floor or ceiling, level it, and allow it to dry. By manually pouring large-fraction expanded clay between timber racks, it can be insulated.

Expanded clay has a relatively high thermal conductivity (0.16-0.16), which is lower than many other materials. It is also fairly heavy when combined with cement, so it is only appropriate for insulating floors made of reinforced concrete. It needs specific skills to use and takes a long time to dry.

The expanded clay layer needs to be covered with layers of vapor and waterproofing because the material is porous and can absorb moisture. Its affordability in the market accounts for its appeal.

What else can you do to insulate??

Other, less common forms of insulation that are also utilized for attic floor thermal insulation should be mentioned:

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

Bulk, natural materials are thought to be an outdated technique that is no longer widely used. Although they are less expensive than others on the market, they have a high level of ignition and the risk of mice living inside of them.

• 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 previously widely used in the USSR and 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, this is a fragile material, heavy, suitable only for reinforced concrete floors.

Average cost of materials in the Russian Federation

The following table displays average prices in rubles for the Russian Federation:

Insulation		Release form	Volume, mass	Price
Mineral wool	Basalt	Plates 12 pcs./pack.	800x600x50 (1 piece.)	900-950
	Glass wool	Roll	20 m 2, 50 mm	1100-1200
	Ecowool	Package	0.12 m 3	100-110
Expanded polystyrene	Styrofoam	Plates	100 mm	300-320/m2
	EPPS	Plates in packaging	13 pcs., 30 mm	1400-1500
Polyurethane foam (spraying service)		Powder	Density 45-60 kg/m3	1200-1300/ m 2
Foamed polyethylene (foil)		Roll	5 mm, 1.2×25 m	850
Wood sawdust		Shavings	car	3500-5500
Fractional expanded clay		Fractions 10-20 mm	bag	1800/m 3
Foam glass		Plates	1 m 3	10100
Rice husk		Husk	ton	1000
Metallurgical slag		Granules	ton	600
Jute		Roller 20 m	5-6 mm,	130-190

The best and most sought after

When it comes to the most widely used insulation available, mineral wool is used to insulate beams and concrete floors in two thirds of all homes.

Its elasticity, thickness, fire resistance, and resistance to moisture are the reasons it was selected.

This is currently the best choice in terms of both cost and quality. It doesn’t need any additional maintenance and is simple to install. For both warm and cold attics, it is utilized.

Though less flexible in form, foam and polystyrene insulation does not necessitate the use of a vapor barrier. Because they don’t crumble and don’t enter the respiratory system or penetrate the skin, they don’t require special installation care. However, this indicator lowers the points for this material because they are more flammable.

Natural materials for insulation are only advantageous when considering the environment; otherwise, they burn extremely hot and become a haven for rodents and parasites.

Granular insulation is very heavy and requires expensive equipment to install in certain cases, but it produces a genuinely warm atmosphere.

The best thermal insulators are sprayed, sealing all gaps, reliefs, and crevices in attics that are both warm and cold. They don’t require vapor or waterproofing, don’t burn or ignite, don’t break down over time, and aren’t appealing to bacteria or rodents.

However, foam ones are still overlooked because spraying work is far more expensive than doing your own tiled or matte insulation installation.

Choosing the appropriate attic floor insulation is crucial to keeping your house cozy and energy-efficient. Because different types of insulation have different advantages, it’s important to take your unique needs and circumstances into account.

Because it is inexpensive and simple to install, fiberglass is a popular option. Many homeowners find it to be a dependable option because of its strong thermal resistance and fire safety. But handling it can be irritating, so wearing the right protective gear is essential.

Excellent thermal performance and environmental friendliness combine in cellulose insulation, which is manufactured from recycled paper products. It works particularly well to seal off holes and fractures, which can lessen energy loss. The drawback is that it might need professional installation and settle over time.

Spray foam insulation is perfect for attics with irregular shapes or difficult-to-reach areas because it has a high R-value and can form an airtight seal. Even though it costs more than other kinds, over time its efficiency can result in significant energy savings.

Another good choice is mineral wool, which is renowned for being fireproof. It provides good acoustic and thermal insulation and is long-lasting. It is, nevertheless, typically more expensive and less accessible than other varieties.

The ideal insulation for your attic floor will ultimately depend on a number of variables, including your attic’s unique characteristics, climate, and spending limit. To help you make an informed decision and evaluate your situation, think about speaking with an expert.

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