How to insulate ventilation in a cold attic: the specifics of thermal insulation of air ducts

A competent device of the ventilation system involves the insulation of air ducts. Otherwise, they are doomed to constantly be covered with condensate, causing irreparable harm. Based on this, the question of how to insulate ventilation in a cold attic is very important, because it is there that there are all the prerequisites for moisture accumulation inside the pipes.

We will tell you all about the purpose and specifics of the thermal insulation device for the ventilation duct system. We will analyze all the options for insulation of air ducts using materials of different structure and purpose. Home masters who want to independently carry out work will find a detailed guide with us.

Arguments for ventilation insulation

The process of condensation accumulation inside an uninsulated ventilation pipe is inevitable. This is a consequence of the collision of warm and cold air currents. To a large extent, condensation loss is facilitated by malfunctions in the system and deviations from the rules for operating premises.

Both moisture settled on the structures and condensate deposited on the walls of the ducts flow down the pipes. Through any leaks at the joints, they will fall on the floors and walls. Because of them, the insulation of the floor gets wet, as a result of which its insulation qualities are reduced at least half.

At a negative temperature, frost appears, and the inner diameter of the pipe decreases. Not only material is destroyed, but also good conditions are created for the life of molds.This threatens residents of the house with frequent respiratory illnesses and allergic reactions.

In order not to create the prerequisites for the dew point, i.e. the transformation of water vapor contained in air into water, air ducts in a cold attic must be insulated

Ventilation in an unheated attic is particularly in need of insulation. Here the difference between the air temperature inside the system and the pipe walls is significant.

Does not require additional insulation only fabric air distribution system. Condensation does not form on the vapor-permeable surface of the textile pipes, and since the channels are dry, microorganisms do not settle in them.

Steam saturation is directly proportional to temperature. The higher it is, the more vapor in the air masses. Even a minimal temperature change reduces the ability of air to retain water in itself in the form of steam. For this reason, condensate builds up at the outlet of the ventilation duct when the air cools.

Where to insulate the ventilation pipe?

Mandatory insulation is necessary in places where a temperature difference occurs. In areas where warm and cold air is in contact, condensation appears most abundantly. Here is the dew point. When designing the insulation of exhaust ducts, the position of this point is calculated first of all.

The challenge is to move it as close as possible to the outlet vent pipe. Ideal when the mixing zone of cold and warm air currents is moved outside the house.

Since this is rare, on a ventilation pipe that crosses a cold attic and then goes onto the roof, the zone of passage through the ceiling of the upper floor or the attic is subject to insulation. The pipe itself is insulated along the entire length until the very conclusion to the roof.

In the case of forced ventilation, the amount of condensate deposited on the outer walls of the ventilation duct is directly proportional to its length. It has an effect on this phenomenon and feature installation. In rooms of a large area, in addition to pipes, valves are also insulated.

In order not to create the prerequisites for the dew point, i.e. the transformation of water vapor contained in air into water, air ducts in a cold attic must be insulated and installed ventilation equipment

The insulated valve has the form of adjustable shutters. The latter limit the passage and slightly increase the temperature of the air supplied from the outside, as tubular heaters are present in the design.

The speed of the air supplied through the valve is controlled by levers or an electric drive system. The heating of the valve blades by heating elements is necessary to prevent their icing. This changes the temperature of the supply air mass slightly.

Thermal insulation materials for pipes

After determining the dew point and performing the necessary calculations, the question remains, how can the ventilation in the attic be insulated, and by what criteria should the material be evaluated. High-quality thermal insulation is possible subject to the correct choice of insulation, its thickness, taking into account the humidity of the air inside and out, temperature difference.

Key selection criteria

There are three main criteria by which insulation material is chosen:

• thermal conductivity level;
• fire safety level;
• material price.

Consider the most popular heat-insulating materials, their inherent advantages and disadvantages. The most popular are mineral fiber based heaters. This group combines cotton wool from slag, fiberglass, basalt threads, thinly elongated during the melting period.

Basalt, it is also stone, cotton wool is distinguished by both characteristics and cost. Slag is harmful to health, and it is better not to use it.

Glass wool for ventilation insulation

Glass wool is most in demand among materials based on mineral fibers.

The main material for the production of glass wool is waste from the glass industry. She copes with her task quite effectively, easily takes the necessary form

The thermal insulation coefficient is from 0.03 to 0.052 VT / m⁰. The heat insulator has long fibers intertwined in such a way that a shell is formed that resembles a cocoon that holds air in it.

The positive technical characteristics of the material are as follows:

1. Fiber thickness - 3-15 micrometers, length - from 15 to 50 mm.
2. Good absorption of noise vibration and acoustic noise due to uniform fiber distribution. This figure for insulated structures varies in the range of 35-40 dB.
3. Fire resistance ranging from NG to G1. Although binder resins are present in the material, it is not self-igniting. Without changes in the structure of glass wool can withstand temperatures up to 250⁰.
4. Resistance to mechanical influences. Early analogues of this insulation did not differ in good resistance to mechanical stress. Modern samples have sufficient strength, good elasticity.
5. The glass wool vapor permeability index is 0.6 mch / Pa, which is almost 2 times higher than that of basalt.
6. Daily sorption hydration - less than 1.7%.
7. The material has good biological stability. Rodents do not settle in it, mold fungi do not breed.
8. Without loss of quality characteristics, glass wool can be compressed 6 times. After expansion, the elastic fibers return to their original position.
9. The average density is 11-25 kg / mᶾ, but the indicator may differ for different manufacturers.

If you do not allow it to get wet, a quality insulation does not shrink during prolonged use.

The stiffness of cotton wool depends on the density. Under the influence of moisture, the thermal conductivity of the material increases. To absorb less moisture, manufacturers add water repellents to the composition

The negative is the increased fragility of the fibers. Working with glass wool is permissible only with the use of protective equipment. So that the thinnest sharp fragments of fibers do not fall into the surrounding space, reliable insulation of the insulation layer is necessary. Protection is also necessary in order to neutralize the destructive effect of sunlight on glass wool.

In addition, glass wool has a relatively short life - about 10 years. When choosing insulation for ventilation pipes in a cold attic, you should definitely be interested in whether the product has a conclusion on compliance with its hygienic and sanitary and epidemiological requirements.

Round ventilation sleeves are insulated with mineral wool. Ventilation pipes with a square section - material in the form of plates. The ventilation duct is first wrapped and fixed with a metal wire or synthetic tape. The second is glued.

Features of the application of basalt wool

This material is an advanced mineral insulation. It consists of molten basalt fibers. Produce it in the form of plates and mats. For round ventilation ducts, ready-to-use heaters are manufactured in the form of cylinders coated with insulation - foil. There are products without an insulating layer.

Basalt cotton wool is non-combustible material. The temperature he can withstand is 1000⁰. The thickness of the stone wool insulation layer does not change with time

The thermal insulation coefficient of the material is 0.034-0.038 W / m⁰. Cheap brands containing formaldehyde resins can be hazardous to human health. In a more expensive insulation, completely harmless biopolymers are used as binders. The price of basalt wool is higher compared to the analog of glass wool.

Polyethylene foam for ventilation insulation

The application of foamed polyethylene on round and square ducts within the attic is a simple and inexpensive option for insulation.

There are several varieties of this material:

1. Usual. This category includes foam rubber (cross-linked polyethylene foam), isolon, and others. Its use is extremely simple - the duct is wrapped in pieces of material and secured with tape.
2. Foil. This insulation is covered on one side with a layer of foil designed to reflect heat and repel moisture. It goes on sale under various names: tepofol type A and B, penofol, mosfol, pharalon, ultraflex. Connect this insulator with special glue or aluminum tape.

The insulation is supplied in roll format with measured length. Among the proposals are self-adhesive options. Their back side is covered with adhesive, which greatly simplifies and speeds up the installation.

For pipes produce insulation made in the form of a shell, these are positions called thermaflex, energy flex, another. It is a ready-made shell in the form of a cylinder, covering communications.

The thermal conductivity coefficient of foamed polyethylene depends on its brand and is in the range 0.031-0.051 W / m⁰.

This material is durable, flexible, resistant to aggressive chemicals, lightweight, easy to install, moderately flammable (class G2). By smoke-forming ability it belongs to the class D3, i.e. forms a large amount of smoke during combustion. It does not apply to environmentally friendly materials, as its decomposition period is two hundred years.

Polyethylene foam insulation has a water absorption rate of 0.2-1%. It is operated in the range of working temperatures -60- + 100⁰ and has a service life of up to 10 years

Depending on the production method, 2 types of polyethylene foam are distinguished:

• PES or crosslinked;
• NPE or non-crosslinked (gas foam).

The first in all respects exceeds the second, but its price is higher. NPE is characterized by the smell of gas. On this basis, it can be distinguished from non-cross-linked polyethylene. Among the disadvantages inherent in polyethylene foam, its high combustibility, low mechanical strength and resistance to UV radiation.

The use of foamed synthetic rubber

This insulation, consisting mainly of closed pores, is similar in appearance to cross-linked polyethylene foam. Unlike the latter, it has increased flexibility. Installation technology is the same as for PES. The same form of release - mats, sheets, rolls, cylinders, but the service life is three times longer.

Rubber cylinders have an internal diameter of 5-300 mm and a wall thickness of 5-150 mm. For easier installation, pipes of large and medium diameters have a longitudinal section.

In the insulated area, the joint is sealed with adhesive. The coefficient of thermal conductivity is 0.024-0.038 t / m⁰. Does not change its characteristics in the operating temperature range of -200 / + 175⁰.

The closed-porous structure of the foamed synthetic rubber makes it an excellent sound insulator. It absorbs about 60% of the noise. This insulation is easy to use.

It is possible to use the material in rooms that are subject to increased sanitary and hygienic requirements. Foamed rubber is moisture resistant, resistant to mold, refers to self-extinguishing materials.

The ignition temperature is above 300⁰. In terms of heat conductivity, vapor permeability, heat conductivity, and leakproofness of rubber compounds, it exceeds analogues of polyethylene foam and polyurethane foam.

Polyfoam as insulation for ventilation pipes

Polyfoam is a foamed mass of plastic containing a large volume of gas. This is a rigid material in the form of pipes consisting of 2-3 parts and connected by means of a tongue-and-groove lock or plates. Only square pipes are insulated with plates.

The advantages of the foam include light weight, resistance to decay, ease of use, low price, service life up to 25 years. The coefficient of thermal conductivity ranges from 0.032-0.05 W / m⁰. Over 30 days, water absorption is 4%. When bending, the tensile strength is in the range of 0.07-0.2 kgf / m². Operating temperatures - -50 / + 75⁰.

Polyfoam, as a heater, has the following disadvantage: liquid can pass through the pores present in its structure. As a result, heat-insulating properties and frost resistance are reduced.

Polyfoam is a common polystyrene foam. It is attractive to rodents, highly flammable, and releases toxins when burned. For installation, a special glue is needed, any other can cause melting of the material.

Extruded polystyrene foam - many protection features

In the production of extruded polystyrene foam, the same starting materials are used as in the manufacture of foam. However, it is precisely thanks to specific technology that a material is obtained that does not have pores and channels in the structure into which moisture can penetrate.

For the same reasons, it retains heat better. Produce it in the form of rigid tubes or plates, goes on sale as Penoplex, EPSS, Technoplex, equipped with spike-groove locks. It has a long service life - up to 50 years.

In the structure of extruded polystyrene foam there are virtually no channels and pores capable of transmitting water / air / heat waves

The coefficient of thermal conductivity of polystyrene foam obtained during extrusion is in the range of 0.028-0.034 W m⁰. 30-day water absorption is 0.4%. Operating temperatures range from -50⁰- + 75⁰. It is characterized by sufficient bending strength - 0.4-1 kgf / m².

PirroVentiDuct thermal insulation for ventilation

PIR boards are a new generation insulation having a rigid cellular structure. It is produced from polyisocyanurate foam. Two sides of the PIR plate are covered with layers of foil. The service life declared by the manufacturers is 50 years. The material is resistant to decay, moderately flammable, but when burned, releases toxic substances.

Direct and shaped elements of the air duct based on PIR plates are obtained by cutting the latter with subsequent gluing of the workpieces with special contact adhesive.

PirroVentiDuct is a material that is heat insulating and structural at the same time. It makes reliable, functional sections for the ventilation system that do not require additional insulation

The thermal conductivity of the material is 0.021 W / m /. The rate of water absorption is within 1%. The compressive strength of the plates is 120 kPa.

The procedure for insulation of ventilation in a cold attic

All thermal insulation measures are carried out according to the norms regulated by SNiP 2.04.14-88. Clear instructions are given here where and how to organize ventilation insulation.

When installing the insulation layer, the main rule should be observed: the insulation should be fastened as tightly as possible so that there are no gaps between the ventilation duct and the insulation. The installation of each of the materials has its own characteristics.

Features of mineral wool insulation

When insulating with mineral wool, one must not forget that it is hygroscopic.

This fact leaves its mark on the order of work:

1. Piping in a cold attic is wrapped with a waterproofing membrane, leaving no gaps or crevices.
2. Winding mineral wool with an overlap, with overlapping previous strips. The layer thickness should correspond to SNiP.
3. A layer of waterproofing is wound over the insulation.
4. The entire structure is pulled together with special bandages.

A rectangular pipe can be insulated with mineral wool in the mats. First, blanks of the required dimensions are cut out, and, having coated them with a pipe, they are pulled together with knitting wire, a clamp or scotch tape.

When working with glass wool, you must remember about personal safety. particles must not be allowed to enter the respiratory tract, eyes

In the outer corners of the air ducts with the installation of insulation there are certain difficulties, it will not be possible to immediately achieve the necessary tightness. Therefore, at the end of the main thermal insulation coating device, the remaining gaps are filled with pieces of material.

Insulation ventilation in a cold attic with expanded polystyrene

If the material is in the form of plates, therefore, it is possible to insulate them with rectangular ducts. The technology of insulation works is the same as when laying mineral wool. The only difference is the optional waterproofing device. The decision is made based on the density of the insulating material.

So, in the case of applying PPS-40, waterproofing is needed, and if PPS-60 is used, waterproofing is optional. Plates must be joined tightly, gaps and gaps must be filled with mounting foam.

Thermal insulation with cylinders

Special shells for insulation of ventilation are made of many heaters:

• mineral wool;
• polyurethane foam;
• polystyrene foam;
• polyethylene.

They are used if they are used for the ventilation of circular pipes. There are several varieties of such thermal insulation:

• one-piece with a longitudinal section;
• two, three, four-section.

Cylinders are selected according to the diameter of the duct. The larger the cross section of the pipe, the larger the number of parts the shell consists of. If it is a solid cylinder, it is opened along the cut and put on the air duct.

No special knowledge is required to install a foam cylinder. Installation consists in compressing parts of the insulation and fixing the connection

The cylinder is convenient as insulation for straight sections. In places where the air duct turns, it will not work. Mats are used in these areas. Among the insulation materials of this type, mineral wool, polystyrene and polyethylene cylinders have the lowest cost. The most expensive option is a shell made of foam rubber.

A very convenient option for insulation of ventilation with your own hands is a self-adhesive insulation, i.e. Penofol brand "C". On one side there is a foil, on the other - a polyethylene film with an adhesive composition applied to it. The adhesive side is protected by an additional layer of film. Before installation, it is removed.

The material is cut to a size corresponding to the perimeter of the duct. At the next stage, the pipe is closed with a heater, folding the edges with an overlap of 50 mm. The joint is sealed with foil tape.

Conclusions and useful video on the topic

How to make insulation of ventilation pipes with your own hands:

Insulation of ventilation pipes with mineral wool and the achieved effect:

In a cold attic, pipes must be insulated without fail. When choosing a material for this purpose should be guided by the design features of the house and their financial capabilities. If the ventilation system is properly insulated, it will be extremely functional, and it will last a very long time.

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