Insulating the attic from the inside if the roof is already covered: materials and technologies

Usually a house is built quickly, often everything is put under the roof during the summer season. After interior decoration, you can move in, improve the local area and expand the functionality of the house. In this article we will tell you how to insulate an attic from the inside if the roof is already covered. The information will help you decide on the choice of material - this often depends on the initial conditions, and will explain the subtleties of its correct use.

Insulation of an already covered roof has its own characteristics that you need to know about Source pinterest.com

After this, you will speak the same language with the builders. Which is a good incentive for them to offer and demonstrate their best and do the work even better.

General points

Let's start with the fact that the attic is a bit of a special room. Its overall structure requires a careful, meticulous approach. And the insulation of the attic roof is even more so:

Mostly vertical or inclined surfaces . Therefore, it is better to immediately exclude all soft “pliable” materials, namely mineral wool rolls.
It is advisable to focus on materials with low dead weight . Since the rafter system is already experiencing significant loads from wind and snow. In addition, the load on load-bearing walls will not increase much.
Often insulation is required for gables . They are not always made by analogy with a main wall. May be made of facing material. Or the frame is simply built for insulation.
It happens that the area of the attic significantly exceeds the size of the house itself , while part of it rests on columns. In this case, you will also have to insulate the ceiling in contact with the street.

If the attic floor protrudes beyond the house, additional insulation of the floor is required. Source metasold.com
It should be understood that the thickness of the insulation must correspond to the weather conditions of a particular climate zone, while having a small margin. To gain the required thickness, the insulation is installed in several layers, and the relatively small dimensions require joining.

Important: splicing any insulation requires a careful approach. The joints of different layers should not be concentrated in one place. To prevent freezing, they should be spaced as far apart as possible. It is important to constantly remember this so as not to spoil the material, especially when insulating a sloping roof.

What is dew point

This is the place in the structure where condensation forms due to the temperature difference between the street and the room. It appears because warm air from around the house accumulates in the form of steam under the roof, and steam, as you know, moves towards the cold air and settles on the under-roof structure in the form of condensation.

Therefore, insulating the attic from the outside is considered an ideal option. Thus, the dew point is moved outside the room. But most often, attic insulation occurs inside, which is why it is so important to follow the sequence of laying the layers of the insulating cake. With this technology, the insulation will not get wet, since the dew point is transferred to the gap between the roof and the insulation.

Preparation

All wooden surfaces must be treated with antiseptic and fireproof impregnations.

All wooden components must be treated with protective materials Source remontik.org

It is necessary to immediately identify “unreliable places” on structural elements. For example, the connection of the outer rafter to a pediment made of facing bricks. Or an overlapping connection between a rafter and a screed, made without insulation. It is necessary to eliminate the shortcomings - if possible, foam them or line them with a sealant. Otherwise, they will not be able to withstand through blowing and freezing.

It is necessary to minimize the use of metal fasteners. This is especially true for metal linings secured with bolts. Of course, the bolted connections will remain, but the plates should be made from thick, durable plywood and replaced. The remaining metal parts are painted with primer-enamel and covered with a layer of polyurethane foam. Metal directly in the insulation is a source of condensation and dampness.

Polyethylene films

This material is laid during the installation of the roof; a prerequisite for use is the creation of gaps for ventilation. This will prevent the formation of condensation, since polyethylene is not capable of allowing air to pass through. Laying with the rough side facing out promotes the evaporation of steam particles.

Polyethylene film can be used for vapor barrier and waterproofing due to its universal characteristics. Reinforcement with a special metal mesh helps increase the strength of the material.

Insulation of the rafter system

It’s great when the insulation of the attic from the inside was planned in advance, or “just in case” the constructive points for this were observed by the builders:

A roofing membrane is mounted on the rafters.
A counter-lattice is provided.
The pitch of the rafters is maintained corresponding to the common length or width of the insulation.

It is convenient to carry out insulation if it was planned at the construction stage Source bamban.ru
It is worth noting that these are ideal initial data that allow you not to look for a “way out of the situation” and to insulate the maximum volume of the attic efficiently without extra costs. Such conditions make it possible to use vapor-permeable insulation. And these are comfortable living conditions.

See also: Catalog of projects of houses with an attic presented at the exhibition “Low-Rise Country”.

Material selection

Let's consider the most popular options for insulating attic walls with your own hands from the inside:

Mineral wool. Inexpensive material, convenient for work. It insulates rooms well and does not accumulate moisture during operation. To lay it between the rafters, it is cut into sheets 1-2 cm wider than the distance between them. The material is inserted into the rafter spaces and, due to elasticity, is tightly held in them.
Styrofoam. This insulation is one of the budget and practical methods of insulation. It is safe for health, does not rot or decompose. But the complete lack of steam conductivity and vulnerability to rodents reduces its effectiveness. Loose joints between slabs also negatively affect heat retention.
Polyurethane foam. Insulation that can be easily applied by spraying onto any surface using a portable unit. The applied layer has no breaks or pores, which has a positive effect on the quality of insulation. The material is not sufficiently resistant to high temperatures.
Ecowool. The cellulose-based material is applied using a spray machine or by hand, resulting in a seamless coating over the entire surface. Requires protection of the resulting surface from moisture with a vapor barrier material.
Foil materials. Compared to traditional thermal insulation, these insulation materials have better properties due to the mirror layer applied to them. This layer reflects the heat coming out of the room back, increasing its thermal protection. Due to the small thickness, savings are created in the occupied volume of the room.

Materials for attic insulation

Insulation of an unprepared roof

When the decision to insulate is forced, the roof is usually not prepared. There is nothing terrible about this, it is even possible to choose the following options:

Insulate with materials that do not require waterproofing.
Build a special frame for living space.

In case of insulation of a roof that is not prepared for this, special compounds can help Source paspraypros.com
Foamed polyurethane foam can play a special role here. Although equipment is required to apply it, insulation occurs in a continuous layer and does not depend on the design features of the roof.

Foamed polyurethane foam is one of them Source da.decorexpro.com

This also includes ecowool. Although its installation requires a roofing membrane, it is quite possible to make a continuous layer of insulation.

Answers to popular questions

What is the best insulation for an attic under metal tiles?

Metal tiles do not place any special requirements on insulation. All types of mineral wool and foam plastics are suitable. The main condition is a sufficient layer of insulation, reliable waterproofing and vapor barrier.

Soundproofing insulation should be installed under a metal roof. Basalt wool and polystyrene foam have these qualities. In addition, roll and block insulation materials with a soundproofing substrate are produced.

How to insulate an attic if the roof is without waterproofing

If there is no waterproofing, it should be installed. With a cold roof, the absence of a water barrier is not critical - if there is no difference in the external and internal temperatures, there will be no condensation, as well as ice dams.

If you install a roofing pie for a warm attic without waterproofing, the insulation will get wet and lose all its performance properties.

The waterproofing film can be laid from the inside, securely connecting the joints. In this case, the need for ventilation under the roofing should be taken into account. Therefore, there must be an additional sheathing above the waterproofing film to create a ventilation gap. If there is no gap, the roofing material is laid on the rafters, then it must be removed.

Waterproofing is laid on top, connected without gaps, sheathing is made and the roofing is installed.

Effective insulation

Next, we will consider the most effective materials that do not require serious equipment in order to efficiently insulate the attic.

Stone wool

Due to their elasticity, the mats adhere well between the rafters and allow installation without additional fastening. And the relatively dense structure of stone wool prevents its shrinkage over time. Therefore, it has proven itself well on vertical surfaces.

Stone wool mats come in different thicknesses, and you can choose the one you need based on climatic conditions and other materials used Source pallazzo.su

To further reduce the risks, every 3 meters of height it is necessary to arrange supports for the insulation - add a horizontal frame element.

Pros and cons of mineral wool

Mineral wool is a heat insulator with a fibrous structure made from mineral raw materials with the addition of synthetic binders. Depending on what raw materials were used, three types of material are distinguished.

Types of material

Stone or basalt. It is made from molten rocks: diabase, basalt, gabbro. Clay, limestone or dolomite is added to them. The binder is a small amount of formaldehyde resin.
Slag-like. Produced from melted blast furnace slag. This is waste resulting from the smelting of cast iron and other metals. May be toxic.
Glass wool. The raw materials for its production are limestone, soda, sand, dolomite and borax. Broken glass and glass production waste are often used.

All types of fiber insulator have different densities. Available in the form of slabs, mats or rolls. The last two varieties are less dense. This is not always convenient at work.

Rockwool stone wool

Advantages

Fire safety. The insulating coating does not ignite or smolder.
Low thermal conductivity values for all types of wool.
Resistant to temperature changes. The fibers do not deform when cooled and heated.
High vapor permeability, which allows the insulator to “breathe”.
Biological and chemical stability. Insects and rodents do not live in mineral wool. Exposure to chemicals does not destroy it.
Convenient and simple installation.

In addition, the relatively low price of the insulator is attractive. But you also need to be aware of its shortcomings.

Flaws

They are few, but they are significant.

High hygroscopicity. In conditions of high humidity or when water enters, cotton wool absorbs a lot of moisture. At the same time, its properties change. The thermal conductivity of a wet coating increases. Moreover, the more water that gets into the cotton coating, the worse it retains heat.
The material is heavier than light insulators: polystyrene foam, extruded polystyrene foam, etc.
All cotton wool is prone to dust during operation, for this reason protective equipment is required.
When choosing insulation for the attic, you must take into account that this is a living space. Therefore, a security certificate is required.

It is better to choose stone wool; slag wool can be toxic. Glass wool is safe, but very dusty. Its small fibers are very sharp, their exposure is harmful to humans.

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Proper completion of work

The insulation has been installed, but the process must also be completed correctly. It must be protected from damp vapors from the room. For this, a vapor barrier film is installed. Moreover, the overall result greatly depends on the thoroughness of execution. Although each package is supplied with instructions, let us briefly repeat:

The subsequent canvas overlaps the previous one by at least 15 cm.
The joints are taped with special tape.

However, attic vapor barrier has a dual purpose. Oddly enough, it also protects the residents themselves. The fact is that vapor-permeable insulation is not strong enough and can be slightly weathered. From the outside this is not so important, plus it is protected by the roofing membrane. And inside it is necessary to exclude even the minimal possibility of the insulation components being released into the air - to reliably cover it.

The final stage is covering the insulation with canvases, on which the finishing is subsequently applied. Source obustroeno.com

Of course, this does not apply to Penoplex. But it is also recommended to protect against it; an effective material is penofol.

As for insulation of any type. In addition to the vapor barrier device, a technique that at first glance is unnecessary, but effective, is often used. Before finishing, intermediate, seemingly unnecessary material is installed. It can be OSB, GVL or GKL - it depends on the design. Moreover, the technology is fully observed - all joints are carefully sealed. This is an additional barrier against the unwanted effects of materials.

Basic mistakes

All the positive aspects of insulation can be negated by errors in their installation:

Carrying out work at low temperatures. This leads to insufficient drying of the glue and loss of strength of the insulating layer.
Wrong choice of material thickness. Insulation of insufficient thickness will not give the desired effect, and a layer that is too thick will lead to unnecessary material costs.
Sliding of thermal insulation due to insufficient fastening. This leads to the appearance of unprotected places and intense penetration of cold through them.
Lack of vapor and waterproofing. In this case, the insulation will get wet, absorbing moisture, and will quickly lose its properties.
Installation of steam and waterproofing films with sagging. These materials should be attached with slight tension.
Lack of ventilation. In an unventilated attic, condensation forms on and inside the walls, damaging the insulation.

When carrying out work on thermal insulation of the attic yourself, it is necessary to take a responsible approach to all stages - from developing the project to attaching the final finish. In this case, a room created with your own hands will delight the owners with comfort for a long time.