What Kind Of Insulation To Choose For The Attic Roof, As Well As The Calculation Of The Required Material

2024 Author: Bailey Albertson | [email protected]. Last modified: 2023-12-17 12:53

Thermal insulation of the attic: from calculations and material selection to installation technology

If the roof of a country house forms a spacious attic space, then it can be used to expand the living space. An attic room can serve as a bedroom or study, a sports room, a cinema or a billiard room. To use the extra space all year round, you need good insulation. Warming the attic will not require large material costs, especially since the work can be done by hand. It is only important to choose a suitable thermal insulation material and carry out the installation correctly.

Content

• 1 Requirements for thermal insulation materials

• 2 What materials are suitable for insulating the attic

  • 2.1 Mineral wool

  • 2.2 Polymer insulation

    • 2.2.1 Styrofoam
    • 2.2.2 Extruded polystyrene foam
    • 2.2.3 Polyurethane foam
  • 2.3 Ecowool

• 3 How to calculate the thickness of thermal insulation

  • 3.1 Table: values of thermal resistances depending on the region of construction
  • 3.2 Table: Coefficients of thermal conductivity of materials

• 4 Insulation of the attic from the inside

  • 4.1 Work order
  • 4.2 Video: thermal insulation of the attic floor with mineral wool

• 5 Features of insulation of the attic roof from the outside

  5.1 Video: everything you need to know about attic insulation

Requirements for thermal insulation materials

The same technology that is used in the construction of frame houses is suitable for insulating the attic, however, increased requirements are imposed on the materials and quality of work. How well the thermal insulation of the attic space will be made affects both the conditions of comfortable living and the durability of the roof. This is due to the fact that the walls of the attic room form gables and roof slopes - those surfaces that are most heated in the summer heat. In winter, on the contrary, blown by cold air currents, they cool down the fastest. If the insulation is of poor quality, then the roof will transmit heat to the outside. One should not think that the danger of such a situation lies in the banal increase in energy consumption for heating the attic. Warm slopes will provoke snow melting, and this is fraught with many more serious troubles - from mechanical damage to the top coating by ice formation to the appearance of fungi and mold that destroy the roofing cake and wooden structures of the truss system.

High-quality thermal insulation will make the attic comfortable for living both in the summer heat and in the winter cold

When choosing a material for insulating an attic, it should be remembered that not only the thickness and number of layers of thermal insulation depends on this, but also the ease of installation. Based on the specifics of the use of heaters, the following requirements are imposed on them:

1. Ability to withstand peak temperatures. The material must be frost-resistant and not degrade at high temperatures, retaining its characteristics even after numerous freeze-thaw or heating-cooling cycles.
2. Durability. The service life of thermal insulation should be no lower, if not higher, than other materials used on the roof. This is due to the fact that replacing a roofing cake is much more difficult than, for example, a top covering made of metal tiles or ondulin.
3. The lowest possible coefficient of thermal conductivity. It is best to take a heater with an indicator of no more than 0.05 W / m × K.
4. Maximum moisture resistance. Since condensation may appear in the under-roof space, the material should not absorb moisture and lose its properties when wet.
5. Fire safety. The thermal insulation must not burn or sustain combustion.
6. Low weight. Insulation should be light so as not to create an increased load on the roof truss system. The total weight of the insulation can be determined by multiplying its density by its volume. Experts recommend using materials with a density of up to 50 kg / m ³.
7. The ability to maintain a given configuration. Insulation is laid in the intervals between the rafters in an inclined position. If you choose a material that can deform under its own weight, then over time it can slide down, forming voids inside the structure. It is necessary to choose thermal insulation that can maintain its original size and shape for a long time.

The choice of thermal insulation affects the thickness of the roofing cake. Later we will look at a way to calculate the amount of material required.

What materials are suitable for attic insulation

You can make the attic suitable for living at any time of the year with the help of various insulation materials. Let's consider their features and highlight their strengths and weaknesses.

Mineral wool

To insulate the attic, you can use glass wool, mineral or slag wool. These materials have the following thermophysical and operational parameters:

• high thermal resistance - up to 1.19 W / (m ² / K);
• low thermal conductivity - no more than 0.042 W / m × K;
• low weight - from 15 to 38 kg per 1 m ².

Wadded insulation is a favorite option for home craftsmen if the roofing cake needs to be equipped from inside the room. It does not support combustion, has a minimum weight, and, which is important, rodents do not start in its layer. Slab samples perfectly retain their shape, and when laying fiber insulation in the space between the rafters, no precise adjustment is required - mineral wool is easily distributed without seams and gaps.

Mineral wool is produced in the form of roll and plate materials

The only drawback is the increased hygroscopicity. Due to the appearance of moisture between the fibers, the thermal insulation properties of the material fall by more than half, and it itself begins to collapse. Therefore, mineral wool needs high-quality waterproofing from the roof and the installation of a vapor barrier membrane from the inside of the attic.

Polymer insulation

Polymeric materials are often used to insulate the roof structure - polystyrene foam and polyurethane foam. They perfectly retain heat and, due to their hydrophobicity, are absolutely not afraid of moisture.

Styrofoam

Simple polystyrene foam, which is also called polystyrene foam, is one of the most popular insulation materials on the building materials market. Good performance characteristics - minimum density, low thermal conductivity, moisture resistance and ability to hold a given shape contribute to the idealization of this material. As a result, it is often used where it is strongly discouraged. Firstly, only G1-G2 non-combustible foam is suitable for insulating residential premises, and not the popular G3-G4, which perfectly ignites and burns out in a matter of minutes. If you choose the latter for insulating the attic, then it will be unrealistic to survive in it in case of fire. Secondly, the installation of ordinary expanded polystyrene is not an easy task, since it is poorly cut and crumbles easily. Thirdly, this material is prone to aging and begins to deteriorate rapidly over time. And in conclusion, it should be noted that foam is a favorite material for rats and mice, therefore it is used only where it will be covered with a layer of concrete screed or hidden behind plaster.

Polyfoam is a type of gas-filled plastic that can be used to insulate an attic space

Extruded polystyrene foam

Extruded polystyrene foam (EPS), which is well suited for thermal insulation of the attic from the outside, is almost completely devoid of the disadvantages of foam. For this, the insulation plates are laid directly under the roofing material, on top of the elements of the rafter system. The extruded polystyrene foam contains flame retardants, so it does not burn well. Compared to polystyrene foam, EPS has higher strength and stiffness, which makes it much easier to install. Like other polymeric materials, extruded polystyrene foam is waterproof, vapor-tight, and has good energy-saving properties. This makes it the best option for outside roof insulation. By the way,EPPS will require very little - a 100 mm layer will be enough to insulate the attic in most regions of our country.

Extruded polystyrene foam is best suited for external roof insulation

Polyurethane foam

Polyurethane foam (PPU) is a gas-filled plastic that is applied in liquid form to the inner surface of the slopes. When set, the material forms a tough foam with excellent physical characteristics:

• heat transfer - up to 0.027 W / m × K;
• thermal resistance from 1.85 to 9.25 W / (m ² / K);
• thermal insulation density - from 30 to 86 kg / m ³;
• weight - from 11 to 22 kg.

For the application of polyurethane foam, a special installation is used in which the liquid mixture is foamed when air or CO _{2 is} supplied.

To insulate the roof with polyurethane foam, you will have to turn to specialists - you cannot do without special equipment and skills.

This method of installation largely determines the advantages of the insulation, since when the roof space is blown out, there are no cracks, gaps and cold bridges in the form of open elements of the rafter system. PU foam does not support combustion and does not change its shape. It does not deteriorate over time and resists moisture well. By the way, the latter factor causes low vapor permeability - the insulation does not allow the roof to "breathe", which is fraught with high humidity in the attic space.

Ecowool

Ecowool can be considered one of the best materials for thermal insulation work at home. This insulation consists of more than 80% cellulose fibers, therefore it has low thermal conductivity and is well suited for filling gaps between rafters. Since cellulose in its pure form burns well and is destroyed by fungi, borax is introduced into its composition as a fire retardant and boric acid to protect it from damage by biological organisms, including rodents.

Basic physical properties of ecowool:

• thermal conductivity - from 0.037 to 0.042 W / m × K;
• density depends on the degree of laying and varies within the range of 26–95 kg / m ³;
• flammability - group G2 according to GOST 30244;
• vapor permeability - up to 03 mg / mchPa.

In terms of its operational properties, ecowool is close to mineral and polymer thermal insulation, ahead of them by many factors. So, unlike mineral wool, it absorbs moisture without significantly reducing thermal conductivity. With an increase in humidity by 1%, a basalt slab will lose a tenth of its thermal insulation properties, while ecowool, when saturated with moisture up to 25%, will increase thermal conductivity by no more than 5%.

Ecowool in the form of slabs of various thicknesses is suitable for insulating the attic

It is also important that when dry, the cellulose insulation completely restores its original characteristics. At the same time, it can serve as a kind of buffer that can maintain a comfortable level of humidity in the room. Ecowool allows installation in a seamless way, therefore it forms a monolithic layer without gaps and cold bridges. Its air permeability is almost half that of mineral insulation, and at the same time it remains elastic enough to dampen sound waves. When using ecowool, the attic will be best protected from external noise. And, finally, it is impossible to remain silent about the environmental friendliness and safety of this material. In its composition there is not a single chemical compound that could evaporate and release substances harmful to humans.

How to calculate the thickness of the insulation

To calculate which layer of insulation is needed for thermal insulation of the attic, builders use the formula from SNiP II-3-79 δ _ut = (R - 0.16 - δ ₁ / λ ₁ - δ ₂ / λ ₂ - δ _i / λ _i) × λ _ut, in which R is the thermal resistance of the slope, wall or floor (m ² × ° С / W), δ is the calculated thickness of individual structural elements in meters, and λ is the thermal conductivity coefficient of the insulation (W / m × ° С) for used structural layers.

In a private household, the formula is simplified to a simple equation δ _ut = R × λБ, where the last factor characterizes the thermal conductivity of the insulation used in W / m × ° С. The minimum thermal resistance of walls, roofs and ceilings depends on the region in which the construction is being carried out.

Table: values of thermal resistances depending on the region of construction

Town	R (m 2 × ° C / W)
	For floors	For walls	For coatings
Anadyr	6.39	4.89	7.19
Biysk	4.65	3.55	5.25
Bryansk	3.92	2.97	4.45
Velikiy Novgorod	4.04	3.06	4.58
Derbent	2.91	2.19	3.33
Ekaterinburg	4.6	3.5	5.19
Irkutsk	4.94	3.76	5.58
Kaliningrad	3.58	2.71	2.08
Krasnoyarsk	4.71	3.59	5.33
Maykop	3.1	2.8	3.5
Moscow	4.15	3.15	4.7
Murmansk	4.82	3.68	5.45
Nalchik	3.7	2.8	4.2
Naryan-Mar	5.28	4.03	5.96
Nizhny Tagil	4.7	3.56	5.3
Omsk	4.83	3.68	5.45
Orenburg	4.49	3.41	5.08
Permian	5.08	3.41	4.49
Penza	4.15	3.15	4.7
St. Petersburg	4.04	3.06	4.58
Saratov	4.15	3.15	4.7
Sochi	2.6	1.83	2.95
Surgut	5.28	4.03	5.95
Tomsk	4.83	3.68	5.45
Tyumen	4.6	3.5	5.2
Ulan-Ude	5.05	3.85	5.7
Chelyabinsk	4.49	3.41	5.08
Chita	5.27	4.02	5.9

The thermal conductivity characteristics of any thermal insulation material can also be found in the tables.

Table: Coefficients of thermal conductivity of materials

Material	λ (W / m × ° С)
Foam rubber (polyurethane foam)	0.03
Penoizol	0.033
Expanded polystyrene	0.04
Basalt (stone) wool	0.045
Glass wool	0.05

Insulation of the attic from the inside

The simplest and most convenient way to insulate the roof is thermal insulation from the side of the attic. For this purpose, practically all known thermal insulation materials are used. Most often, mineral or glass wool is used - the low price of these heaters affects. Extruded polystyrene foam is used a little less often, the installation of which causes more difficulties. And unfortunately, ecowool or expanded polystyrene blowing is still very rarely used - the relatively high price and complexity of installing thermal insulation play a role here.

When insulating the attic from the inside, not only the walls are insulated, but also the floor

The durability of the materials used and the comfort inside the attic depends on how accurately the technology of thermal insulation measures is followed. The most important role here is played by how well the roofing "pie" is laid. If we consider the structure from the inside out, then it consists of the following elements:

• finishing with sheets of drywall, plywood or OSB, clapboard, etc.;
• crate with ventilation gap;
• vapor barrier;
• thermal insulation material;
• waterproofing;
• counter-lattice and lathing with a ventilation gap;
• roofing material.

It should be noted that vapor barrier is only needed when cotton materials are used for insulation - in this case, it will prevent the penetration of moist air from the attic. When using polyurethane foam or polystyrene foam, there is no need for a diffusion membrane.

As for waterproofing, it is needed in any case, since it will serve as an additional barrier to protect the roofing cake and wooden elements of the rafter system from moisture coming from outside. If fibrous heaters are used for thermal insulation, then superdiffusion membranes are used that can pass water vapor in one direction. During installation, they are oriented in such a way as to ensure the removal of moisture from the cotton materials. In addition, to improve ventilation between the waterproofing and the roof, a ventilation gap with a height of 5 to 10 cm is arranged.

When insulating with mineral wool, it is necessary to use a vapor barrier film

The whole process of roof insulation can be divided into several stages:

• preparatory work;
• preparation of thermal insulation material;
• laying the insulation in place;
• fastening of thermal insulation;
• finishing activities.

It is necessary to remember about the insulation of the attic room, starting from the design stage, not forgetting to take into account the peculiarities of thermal insulation work at all stages of construction. It should be decided from the very beginning what the walls of the attic will be. If the sloped surfaces of the roof will act in their capacity up to the very overlap, then the roof slopes are insulated. In the event that vertical wall structures are to be installed, thermal insulation is installed on the involved roof sections, walls and adjacent overlap sections.

Thermal insulation is installed in the areas used

Work order

Before proceeding with the thermal insulation of the attic, the insulation cake should be protected with a layer of waterproofing. This work must be done before laying the roofing material, otherwise it will not be possible to achieve complete tightness of the thermal insulation carpet. They begin to lay the membrane membrane directly on top of the rafters. The work is carried out from the bottom up, with an overlap of the previous canvas by 15 cm and gluing the joint with special tape. It is not necessary to stretch the film, it is better to leave a little slack. A deflection of up to 20 mm per 1 running meter of material will be enough so that the membrane waterproofing does not break with the onset of winter frosts. It is best to use a construction stapler to attach the film to the rafters. If such a tool is not at hand, then the waterproofing can be nailed with galvanized nails with wide heads.

You should think about protecting the thermal insulation cake from moisture even at the stage of building a roof

To ensure normal ventilation of the space between the film membrane and the roofing material, lumber with a thickness of at least 25 mm is used as a lathing. They are attached to the rafter legs using corrosion-resistant self-tapping screws or galvanized nails 50–70 mm long.

If the roof is covered with a soft roof, then a solid base of chipboard, OSB or moisture-resistant plywood is mounted on the crate. Metal tiles, slate and other rigid roofing materials are attached directly to the sheathing elements.

Then the installation is carried out from the attic side. In order not to make mistakes, the sequence of work should be observed:

1. The thermal insulation material is unpacked. Plate and roll insulation is laid out on a flat surface and left for a short time to straighten its fibers.
2. A sheet of mineral wool is cut into pieces, the width of which is 2-3 cm longer than the pitch of the rafter legs.

3. The cut plates of insulation are placed in the gaps between the rafters. Initially, the insulation will be held due to the installation of the "vaspor", so each canvas is first pressed in the center, and then its edges are tucked in so that the insulation does not protrude beyond the rafters.

   

   Insulation is laid from the bottom up, pushing the material into the gaps between the rafters

4. Mineral wool is covered with a vapor barrier membrane. As in the case of waterproofing, the strips of material are laid horizontally, from bottom to top, with an overlap of at least 10 cm. The joints are glued with tape, and the film itself is attached to the rafters with stapling staples.

5. The bottom lathing is made of lumber 2.5 cm thick. In the future, plasterboard structures or other finishing material will be attached to it.

   

   A layer of insulation is closed with a vapor barrier membrane, on top of which the battens are stuffed

Sometimes it is necessary to equip an insulated attic in a house with an already installed roof. In order not to dismantle the roofing material, the waterproofing membrane can be installed from the side of the room. To do this, the rafters are wrapped with a film, and the material itself is attached to the crate. The disadvantage of this solution is that the wooden roof structures remain unprotected if moisture begins to seep inside for some reason.

Video: thermal insulation of the attic floor with mineral wool

Features of insulation of the attic roof from the outside

If the design of the attic room assumes the presence of wooden beams on the walls or its size does not allow using a single centimeter of space, then the roof is insulated from the outside. It is best to do this even at the stage of roof construction, since otherwise you will have to remove the roofing material.

Insulation of the roof from the outside can only be done with rigid thermal insulation. The best material in this case is extruded polystyrene foam. As noted above, such a coating does not need a vapor barrier, so the insulation cake consists of fewer layers:

• plate thermal insulation;
• waterproofing membrane;
• crate with ventilation gap;
• roofing material.

The main advantage of external roof insulation is the homogeneity of the thermal insulation layer. The undoubted advantage is the absence of cold bridges and the possibility of inspecting and repairing the rafters without dismantling the roofing material.

The way in which the attic is insulated from the outside will increase the internal space of the attic and use the rafters as decorative elements of the interior

Work order:

1. A solid base of plywood or OSB is laid on the rafters. The material is fastened with corrosion-resistant self-tapping screws and the places where the rafters pass are marked.
2. A wooden beam is stuffed onto the lower part of the wooden base, which will serve as a support for the sliding insulation plates. Its section must correspond to the thickness of the thermal insulation layer.

3. Polystyrene foam plates are laid out on the prepared surface. Laying is carried out in a checkerboard pattern, starting from the support bar. For fastening thermal insulation, special dowels with a wide head are used.

   

   Installation of polystyrene foam plates in two layers will avoid cracks and eliminate cold bridges

4. Insulation plates are covered with waterproofing. The strips of material are spread from the bottom row of the insulation and gradually move up. In this case, each subsequent sheet of the waterproofing membrane should go over the previous one by at least 10 cm. The joint is glued with tape.
5. Guided by the marks made earlier, sheathing bars are nailed to the rafters. In order to ensure normal ventilation of the roofing space, choose sawn timber with a cross section of at least 40 mm.

All that remains to be done is to lay and fix the roofing material. Rigid types of coverings are attached directly to the crate, therefore, the distance between the timber should be taken into account during the installation stage. A solid base of OSB or plywood is installed under the soft roof, which is protected with a layer of waterproofing. In this case, there is no need to install a waterproofing membrane over the insulation.

Video: everything you need to know about attic insulation

Thermal insulation of the attic room, besides, in fact, keeping heat inside, allows you to solve a number of other problems. High-quality insulation will prevent the roof from overheating in the summer, which means that the room will be as comfortable as in any other room. In winter frosts, the thermal insulation cake will prevent snow melting and ice formation, and during rain or hail it will serve as protection against noise. It is only important to take into account the features of various heaters and do the work correctly, taking into account the rules and installation technology.