Ventilation plastic pipes for hoods: the nuances of selection and installation

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Tatyana Zakharova
Last update: March 2019

Laying communications in a house or apartment is not as simple as it seems at first glance. In order for the equipment to work normally, and also there should be no complaints from the inspecting authorities, it is necessary to carry out installation taking into account all the norms and rules, not forgetting the aesthetic component.

We will tell you how to correctly select the best pipes for hoods, focusing on their technical and practical qualities. Here you will learn how to choose the optimal section and calculate its size. Together we will understand the set of components from which the ventilation ducts are assembled.

For independent masters, we offer two options for installing plastic ducts. The information submitted for consideration is supplemented by diagrams, photo collections, video guides.

The use of ventilation pipes in the home

Ventilation pipes with a set of connecting and fastening elements are called ducts. They are designed to ensure air circulation and are installed in those rooms where there is no access to the natural movement of air or there is an additional need for ventilation: in kitchens, in bathrooms, toilets.

Before plastic parts appeared on the market, air ducts were made of galvanized metal, and now they are often found in production shops or in public catering establishments (their use is associated with high temperatures).

But for domestic use, that is, for the installation of ventilation in apartments and cottages, they are more suitable polymer products.

They have the following advantages:

  • have less weight than metal, so they are easier to install with your own hands;
  • smooth walls have minimal resistance to air movement;
  • tight because they have no seams;
  • resistant to high humidity, do not rust;
  • On sale you can always find a set of fittings that fit the cross section.

Products that meet GOSTs and have certificates of conformity are allowed for sale, so you can talk about the safety of plastic elements.

Air Duct Parts
A stand in a supermarket with plastic elements for assembling the ventilation system for the hood: rectangular and round tubes, adapters, tees, plugs, corner pieces

Key Features of Plastic Parts

The properties of pipes must be known in order to properly design and install a ventilation system in an apartment or house. The characteristics of the elements may vary depending on the installation location (above the drywall ceiling, in the closet, in the attic) and the geometry of the room.

Consider which features are decisive when choosing.

Duct Material

On sale you can find products for creating ventilation structures from four types of material, which in everyday life are called plastic:

  • polyvinyl chloride;
  • polypropylene;
  • polyurethane;
  • polyethylene.

Polyvinyl chloride. Lightweight, inexpensive, easy to install PVC ducts are the most common material for the construction of household ventilation structures. They are durable, airtight, but have some limitations.

They can not be heated to 160 ° C, since chlorine harmful to all living things begins to be released, and according to the standards, the upper heating bar without risk to human health is + 120 ° C.

Installation of PVC pipes
PVC pipes are suitable for installation in the kitchen or in the bathroom, their use is prohibited where there is a possibility of heating to 160-180 ° C - for example, in saunas or in rooms with a fireplace

When the temperature drops below + 5 ° C, PVC becomes brittle, so for the installation of the ventilation system in rooms with temporary residence, it is better to choose a different type of pipe, for example, polyethylene or vinylurethane.

Polypropylene - an excellent dielectric, not hygroscopic, has high resistance to aggressive chemical environments. The tensile strength is about 4 times higher than that of high-pressure polyethylene products.

The main disadvantage is combustibility, the maximum possible temperature is + 85ºС. However, there is a fire-resistant variety with flame retardants - PPS.

Polyurethane in its characteristics resembles PVC, but can withstand higher temperatures - up to + 280ºС.

Reinforced polyurethane pipe
Particularly strong is a vinyl urethane reinforced with a steel spiral. It is suitable for drawing, as it has excellent resistance to mechanical damage and flexibility, allowing you to turn the duct at any angle

PND - low-pressure polyethylene. It does not crack over time and, unlike PVC, tolerates negative temperatures more easily (relevant for homes with temporary residence). Possible heat resistance - up to + 80ºС, cooling - up to -50ºС. Easy to process, like all types of plastic products.

Polypropylene and polyethylene pipes for household ventilation are rarely used, their PVC products are leading.

Types of pipes by degree of flexibility

There are two categories of ventilation plastic pipes for hoods - rigid and flexible. Sometimes a combined option is needed, but much less often. If the hood is installed near the vent, there is no need for a complex design.

When purchasing rigid pipes of round or rectangular cross-section, it is necessary to purchase a set of additional parts in order to make turns or transition points.

PVC assembly
To assemble a short exhaust duct placed above the kitchen cabinet, rectangular PVC channels and connecting corner elements of the same material were used

Along with rigid straight pipes, corrugation is used - flexible polyurethane products or aluminum, allowing you to do without corner parts.

Corrugated Pipe Application
The use of an aluminum corrugated pipe as an air duct, which has two advantages over plastic analogues: fire resistance and higher strength

Corrugated products are more economical, but lose in design. To preserve the beautiful appearance of the interior, it is better to disguise them under suspended structures or place them in the “blind” zone - on cabinets against the wall.

Varieties of elements in sectional shape

Depending on the configuration of the pipe, air ducts of the following types are distinguished:

  • round;
  • rectangular;
  • flat.

The shape of the cross section largely affects the technical characteristics and installation method. For example, direct round pipes They have better throughput and excellent sound insulation, since air moving along smooth walls practically does not encounter obstacles (with the exception of corner sectors).

However, installation problems may occur due to the cylindrical shape.

Round pipe mounting diagram
The option of installing a pipe of circular cross section leading from the hood to the ventilation hole on an adjacent wall. Mounting elements: 4 pipe sections, 3 round 90 ° elbows, gear (+)

Rectangular ducts tightly fit to any flat surfaces (walls, ceiling, walls of kitchen cabinets), so it’s much easier to install them. But there is one drawback - the uneven distribution of air, due to which there is a lot of noise.

Plastic pipe hood
The optimal solution for installing ventilation over a suspended ceiling: lightweight rectangular plastic pipes with a set of adapters and an output round pipe (to reduce noise)

Flat ducts - these are the same rectangular, but having a large difference in the dimensions of the width and height of the cross-section (for example, flat channels 110 mm x 55 mm).Due to their compactness, they are often used for installation with a lack of free space (for example, over hanging structures or over highly suspended cabinets).

How to choose a section size?

The size of the cross section is more important than its shape, since the efficiency of air exchange in the room depends on this parameter. There are standards that take into account the specifics of various rooms, and when choosing ventilation elements it is better to focus on them.

Air exchange requirements table
Rooms with high humidity and a high content of dirt in the air (bathroom or kitchen) should be ventilated more often and more intensively than relatively clean and dry (bedroom, living room) (+)

According to SNiP, the volume of air flow in houses and apartments should be at least 3 m3/ hour at 1 m2 living space, while the number of people living is not taken into account.

The volume of circulating air for people who are constantly in the room - 60 m3/ h, temporarily located - 20 m3/ h (refers to places of work, for example, offices).

It is not possible to independently calculate the cross section independently, but there is simplified calculation methods. However, perfectionists are better off using the services of an engineer or a special program for which the following data will be needed:

  • duct shape;
  • pipe manufacturing material;
  • internal resistance;
  • indoor temperature.

There is a method that allows you to determine the size of the ventilation hole by the area of ​​the room. For every square meter of the room there is 5.4 cm² of duct section, and the pollution factor is important.

For the exact choice of the pipe cross-section, we recommend contacting professionals who make calculations using complex formulas based on specific data.

What does exhaust ventilation consist of?

For the installation of air ducts, one pipe is not enough, shaped elements are needed - fittings for various purposes. They serve to tightly connect parts into a single system, provide smooth transitions of pipes of different diameters, connect the duct with an exhaust hood and ventilation hole, and allow you to create 90º angles.

Plastic fittings
Plastic fittings for assembling a rectangular duct: connecting and horizontal elbows, plugs, holders, grilles, gearboxes, straight connectors, plates, tees

One of the important elements is the transition (adapter). It is necessary in two cases: when you need to connect pipes of different cross-sections or ducts that differ in size.

They are used for assembling structures in rooms of complex geometry, sometimes for fragments built into cabinets.

In order to avoid the effect of backdraft and used air does not return to the room, the air ducts are equipped with a check valve.

This is a built-in frame with a dynamic blade that opens in only one direction - along the air flow into the ventilation shaft. The valve does not act as a connecting element, but as a part that increases the efficiency of ventilation.

Using fittings
The assembly of a small segment involves two pipe sections with a rectangular cross-section, a wall plate, a duct connector with an outlet, and an angular horizontal bend

To ensure absolute sealing, it is necessary to select fittings strictly according to the size of the pipes: for example, for boxes of 150 * 100 mm, elbows of the specified size are also necessary.

Plastic pipe mounting options

Consider two options for installing plastic pipes for exhaust ventilation. They differ both in the place of installation and in the choice of elements.

Option 1. Indoor duct installation

Most often plastic pipes for arrangement of ventilation used in the kitchen to connect the hood and the ventilation hole located on the wall under the ceiling. To facilitate operation, the hob must be positioned as close as possible to the outlet.

If it is installed on the opposite side, it is better to move it closer than to pull the duct through the entire kitchen.

The shorter the overall pipe length, the better. It is estimated that each rotation of the pipe with an angle of 90º reduces the efficiency by 10%, and that systems that are longer than 3 meters lose as much for every extra meter.

In order not to raise questions during the course of work, we produce preliminary calculations and draw up a drawing indicating the dimensions and additional parts of the duct.

Installation of a plastic box
As a sample, we take the often-encountered option, when the exhaust outlet is located slightly to the side of the hood

To work, you will need:

  • flat channel for exhaust ventilation 204 * 60 (1.5-2 m);
  • horizontal knee 204 * 60
  • connecting knee;
  • wall plate;
  • round gearbox with adapter;
  • plastic hacksaw;
  • sandpaper;
  • sealant;
  • marking tool.

We prepare the pipes - we cut the blanks of the desired length from the plastic boxes to clean the edges. If the duct is mounted in free space, you can pre-assemble it on the floor, fixing the connecting elements with a sealant.

If part of the structure will be in the cabinet, first we fix it (gearbox + vertical pipe), then connect it to the horizontal pipe with an angular bend.

At the end, we connect the pipe to the hole decorated with the plate with a special fitting. For strength, anoint the joints with sealant, heating can not be used.

Duct mounting schemes
False ceiling structures or wall cabinets are used to mask the duct. For open space, it is better to choose flat rectangular boxes that become invisible if placed on cabinets (+)

If mounting to a wall or ceiling is necessary, self-tapping screws cannot be used. For this purpose, clamps are tightly provided to tightly enclose the pipe. They are equipped with a rubber seal and are attached using brackets or studs. Some clamps are fixed by a simple snap-on, which simplifies the installation process.

Having chosen a suspended ceiling as a masking structure, try to conduct quality work. Before starting construction, carefully check the air tightness of the duct - for repair or replacement, you will have to disassemble the ceiling structure made of plastic panels or drywall.

In the construction of ventilation ducts, not only plastic products are used.You will learn about the choice of material for ducting from popular article our site.

Option # 2. Thermal insulation of pipes in the attic

In a city apartment, the installation of exhaust ventilation is reduced to installation of plastic ductsleading up to the hole in the common house shaft. In a private house, it does not end there, since there is another section - from the heated room through the attic to the street.

To prevent condensation on the plastic pipes from the cold (the attic is often not heated), produce insulation.

The best materials for thermal insulation are:

  • basalt cotton wool (glass wool, mineral wool);
  • shell made of polymeric materials - polystyrene or polystyrene;
  • foamed polyethylene.

An example of basalt wool is Rockwool coiled mineral wool, non-combustible and tear-resistant, with a minimum breathability of 0.3 mg / m × h × Pa, a wide range of heat resistance (from - 180 ºС to + 500 ºС), hygroscopicity of about 1.5% by volume . Service life - up to 35 years.

Roll insulation for ducts
In addition to roll basalt wool, there are other varieties of Rockwool insulation: thick mats or plates, coiled cylinders with foil coating

Soft rolls are wrapped around the pipes with an overlap, covered with foil or roofing material on top (if mats without waterproofing are used), fixed with a metallic tape or steel wire by winding.

Polyfoam and expanded polystyrene look like rigid tubes consisting of several segments. Some of them are covered with a layer of foil. The foam has a looser structure, so it is suitable for warming curved fragments. Due to the low price it is preferred by thrifty owners.

PPP shell characteristics
The table shows the comparative characteristics of the shells of PPS, which are made of PSB-S foam and look like half cylinders, fastened with clamps or bandage (+)

The leading position is held by foamed polyethylene Penofol, more elastic than the listed materials. The insulation is notable for its minimum thickness, but it does not allow moisture to pass through (it is covered with waterproofing foil on one or two sides), provides a low noise level and perfectly retains heat.

Installation of Penofol
For independent insulation, we recommend using Penofol C roll. The secret to easy installation is contained in its structure: thin and lightweight polyethylene is covered with an adhesive layer on one side and a waterproofing foil on the other.

The thickness of the insulation is different - from 3 mm to 10 mm, the coefficient of thermal conductivity in the range of 0.038-0.051 W / (m * K), water absorption - up to 0.35%. For installation, it is enough to cut the material into pieces of the desired size, remove the protective film and stick it on the pipe fragment.

For straight pipes, large in length, you can use the roll to the full width, without cutting.

Particular attention should be paid to the joints, the zone of exit of the duct to the roof, places of contact with the outer walls.

Conclusions and useful video on the topic

Informative videos will help you understand the types of plastic pipes and learn more about how to install them.

Video # 1. Installation of a plastic box:

Video # 2. Installation procedure in a drywall box:

Video # 3. Thermal insulation of ventilation pipes in the garage:

As you can see, the installation of plastic ducts is not difficult and is suitable for independent work. However, when designing a project, we recommend contacting professionals who know the nuances of the supply and exhaust ventilation installation and are able to accurately calculate the dimensions of the elements used.

If you have any questions while familiarizing yourself with the information presented by us, please write comments in the block below. Here you can talk about your own experience in installing ducts and share useful information.

Was the article helpful?
Thanks for your feedback!
No (13)
Thanks for your feedback!
Yes (90)
Visitors Comments
  1. Vitaliy

    I have a corrugated vinyl urethane pipe. An extremely convenient thing, it can be both stretched and squeezed, as well as bent at the right angle. Suitable for any occasion: if the hood is low above the equipment, or high, almost under the ceiling. This pipe is already ten years old, everything is in perfect order with it. And there were no problems with the installation at the time, I set it myself. I recommend to all.

  2. Kirill

    There is a friend who violently opposes pipes from the corrugation. He had installation experience (unsuccessful), with incorrect calculations, so he complains not of his amateurism in the installation, but of the material. Personally, I don’t see much difference between PVC pipes and corrugation, the whole snag is in the correct installation, well, so that it fits into the interior. Corrugation, by the way, is cheaper, and mounting is also easier.

    • Expert
      Alexey Dedyulin

      Smooth-walled air ducts, Cyril, have the least aerodynamic drag and least noise generation. Of course, the length of the apartment, part of the cottage ducts is not enough for a noticeable manifestation of this characteristic. The aerodynamics of ducts are the subject of several studies. Attached a screenshot with the intermediate conclusions of one of the studies.

      Attached photos: