Each residential building and building for any purpose needs to be insulated. This procedure can be applied to floors, ceilings, foundations and walls. No dwelling or institution can be operated without ventilation through which heat escapes. This means that such a system also needs thermal insulation.
Why thermal insulation is needed
It allows you to solve three main tasks. First, you can prevent condensation from forming. Secondly, to reduce the noise of the equipment. Thirdly, you can reduce heating costs.
Choice of material and its types
To carry out the thermal insulation of the duct, it is necessary to select the material. These can be cylindrical shells, roll materials or sheet products. In the latter case, we are talking about a variant that is suitable for square and rectangular ducts. But in the case of systems of a different configuration, sheet thermal insulationused quite rarely. This is due to the complexity of installation and the increase in the time of work. In addition, you have to make a lot of joints, which weaken the structure.
Excellent replacement is roll insulation. The basis is usually mineral wool. Its thickness varies from 40 to 80 mm. The most popular format is 50 mm. Quite rarely, mineral wool 80 mm thick is used. Such solutions for thermal insulation of ventilation ducts are relevant for large-panel housing construction, but not for a private residential building.
Mineral wool and polyethylene foam
If you use mineral wool with an outer foil layer, you will not only be able to make the structure more efficient, but also protect it mechanically. It is important to keep in mind that cotton wool gradually becomes caked, and over time it will begin to crumble, so you need to be careful when working with it.
Thermal insulation of air ducts is often carried out with polyethylene foam. Such work is cheaper, since the cost of materials is less. The insulation has a small thickness, so the pipe must be wrapped with polyethylene several times. According to its characteristics, this material is similar to foamed rubber. Among the roll options, mineral wool insulation is considered as a priority.
Insulation shell
The shell can be monolithic (in this case, it is strung on a pipe) or a team. The latter option is used for ready-made operating systems. Shellcan help out in those places where the pipe is passed through the wall. When winding roll insulation in such cases, it may be difficult. Pretty good results can be achieved in outdoor open areas. However, those points where the duct turns cannot be closed with a cylinder. In such conditions, the use of insulating mats is recommended.
The shell can be made from:
- Styrofoam.
- Mineral wool.
- Extruded Styrofoam.
- Polyethylene.
- Rubber.
In the supply and exhaust air ducts, there is a lot of noise during operation. With an increase in the cross section of the pipe, the throughput becomes higher, but the resistance also increases. Interior finishing allows you to make the surface as smooth as possible, which slows down the air flow less.
Mufflers and foams
Combined insulation solutions are rarely used today, as more practical solutions are available on the market. Silencers can significantly reduce noise. In addition to mineral wool, glass wool can be used for thermal insulation, which is covered with reinforced aluminum. Inside is fiberglass with impregnation. You can also use foam elastomers. They are good because they die out when exposed to fire and do not support combustion. Such materials have an additional number of features, they are:
- Do not allow mold to grow.
- Absorb moisture.
- Harmful to microorganisms.
- Let steam through without harm.
Thermal insulation of air ducts is quite often carried out by the following materials:
- Polyisocyanate.
- Chloridepolyvinyl.
- Polystyrene.
They are fireproof, like polyethylene and polyurethane. These materials are supplied in the form of tubular sectors, blocks and plates. The main area of use is internal thermal protection. On the basis of phenol, expanded resins are made, which are fireproof and stably tolerate the effects of microbiological substances. For this reason, they are placed in the air ducts of industrial refrigerators.
What to look for before starting work
Choosing the right material for thermal protection is quite difficult, so some factors should be taken into account. First, it is important to consider where the pipes are located - in the room or on the street. Secondly, it is necessary to take into account the diameter and thickness of the pipe. Third, you need to pay attention to the main structural material.
If we are talking about domestic ventilation, it is insulated with polyethylene foam. From it, ready-made shells are made that take the form of a pipe. With their help, you can isolate the system from hypothermia. The advantage of these materials is the absence of harmful substances in the composition. If it is necessary to simultaneously insulate the gas pipeline and ventilation pipes, mineral wool must be used.
Technique for performing work. Step by step instructions
Whenthermal insulation of air ducts, which are located outside the heated premises, insulation is carried out from the outlet to the deflector. If the pipe goes through the attic and passes through the roof, it must be insulated throughout the length of the segment in the attic. The same requirements apply to the zone that goes through an unheated room.
The heated supply system is equipped with the appropriate material throughout. The use of boxes is often resorted to in attics. Thermal insulation in this case has the form of casings and consists of foamed polyethylene. Among the advantages of this approach, one should highlight the affordable cost and the ability to purchase goods in any hardware store. The casing is recommended to be selected taking into account the size of the pipe.
Polyethylene foam can deteriorate when exposed to ultraviolet light. To eliminate this effect, it is necessary to cover the outside of the structure with aluminum kitchen foil. When performing thermal insulation of supply air ducts, it is necessary to measure the diameter and height of the system from the outside. Next, a casing of the desired size is prepared. If an umbrella is installed, it must be removed. The casing is stretched to the base of the pipeline. The umbrella can then be returned to its place.
Foil is applied from bottom to top on the system. This will increase the life of the structure. With the help of copper or stainless steel clamps, the winding can be fixed. If the work is carried out in central Russia, this solution is best suited. If we are talking about a more severe climate, you will need a reinforced insulation like a mineralcotton wool. It works well on domestic and industrial ventilated ducts. If desired, the material can be used inside and out. A typical example is Isover coatings.
Required tools
When installing duct insulation, prepare the following tools:
- Spatula.
- Stapler.
- Square.
- Scotch.
- Sharp-sharpened construction knife.
- Ruler.
- Roulette.
- Marker.
The spatula must have a rubber working part. The tape must be aluminum, the thickness of the strip is 7.5 cm. The marker is required for marking.
Expert Tips
Before cutting the insulating material, when calculating the required width, it is necessary to build on the diameter of the pipe. Double the thickness of the insulation should be added to this value. The amount is increased by 3.14 times. This will allow you to get the desired indicator. The roll is unwound and the required distance on it is measured. When measuring, it is important to exclude wetting of cotton wool. If it's raining outside, it's better to delay preparation than to lose an expensive product.
When you make an incision on the surface, you need to separate the cotton layer from the foil. When the roll is cut, according to the prepared mark, it is necessary to wrap the pipe into it. Every 10 cm, it is necessary to fix the seam with a stapler and glue the connected area with tape.
After that, a rubber spatula is passed over the adhesive tape, then the glue will better grab the surface. If workis carried out with pipes that supply the house with air, it is necessary to cover the system from heat leaks also at the joints. This problem can be solved quite simply by cutting curved pieces. Their length is selected in accordance with the calculated values. Fragments should be exposed so that they duplicate the problematic bend. The joints must be covered with aluminum tape, which can be leveled with a spatula.
The shell is fairly easy to work with as it is applied in place and snapped into place. Thermal insulation of ventilation ducts can be difficult where air separation occurs. When working on industrial installations, materials should be used that are capable of preventing knocking or burning, but shock sensitivity is not important. Sections of air ducts that are located outdoors cannot be insulated with mounting foam.
Thickness calculation
The thickness of the thermal insulation of air ducts is directly proportional to the thermal conductivity and inversely proportional to the heat transfer coefficient. The layer thickness is set taking into account:
- Differences in air temperature in the system and in the room.
- Duct parameters.
- Temperature and humidity inside the building.
- Insulation thermal conductivity.
Calculation of thermal insulation of air ducts is carried out taking into account the dew point temperature, which depends on the humidity and air temperature in the room. It is important to pay attention to the thermal conductivity of the material. Fromthickness will depend on it.
If the coefficient is 0.03, the optimal final thickness value is 1.9 cm.
With a coefficient of 0.032, the thickness should be increased to 2.1 cm.
The thickness increases to 2.3 cm if the thermal conductivity is 0.034.
The thickness will be 3 cm if the coefficient is 0.04.
Self-adhesive duct insulation typically has a coefficient of 0.038. For this value, the thickness of the material must be 2.8 cm.
Description of self-adhesive thermal insulation
Sheet thermal insulation with a self-adhesive layer is made of polyethylene foam. The degree of firmware reaches 60%. The coating is aluminum reflective foil. The thickness of this layer is 70 µm. The density of the material is 29 kg/m3. The temperature range for operation varies from -60 to + 80 ˚С. The thermal conductivity coefficient is 0.037. It is measured at a temperature of +40 ˚С.
Self-adhesive thermal insulation for air ducts belongs to the first group of fire safety. The material is packed in a roll, the width and diameter of which are 0.98 and 0.76 m, respectively. Installation of the material is quite simple thanks to the self-adhesive layer of cross-linked polyethylene. The insulation is flexible so it can be used for radiators without removing them.
Conclusion
The calculation of the thickness of the thermal insulation of the duct is extremely importantstage at work. If this indicator is chosen incorrectly, the system will work with less efficiency. You may find that the heat loss will be increased. Materials for thermal insulation of air ducts are usually selected taking into account the purpose of the premises. A very important factor is the safety of insulation for residential buildings.
