How to lay the membrane - inside out or face down? Choice of material - Installation of vapor-permeable film + Photo and Video

How to lay the membrane - inside out or face down? Choice of material - Installation of vapor-permeable film + Photo and Video The vapor-permeable membrane is a film that excludes the ingress of water, but perfectly passes steam into one the other side.

Vapor barrier or vapor barrier is called a film that completely excludes the passage of both water and steam.

IMPORTANT! There is no universal membrane! There is a vapor-permeable membrane and a vapor barrier of completely different concepts with completely different purposes. Incorrect use of these films leads to the destruction of the structure!

General information

After the final stage of construction, when it's time to warm up the roof and walls, use special films. They are placed under a layer of insulation material.

For internal work, the obstacles to evaporation must be taken into account, which excludes the presence of pores and perforations. It is preferable to use a polyethylene reinforced film. It is good if the coating is made of foil with an aluminum base.

This vapor-permeable membrane prevents condensation. And it becomes irreplaceable when working with galvanized materials, corrugated board, etc.

Such membranes have different levels of vapor permeability. This is a daily indicator of the permeability of moisture in the form of steam through a square meter of film. If this indicator is equal to several grams, we consider this sample to be vapor barrier.

If the indicator is from 100 to 1000 grams, this is a vapor-permeable membrane and it has several functions:

  • Protect from external moisture;
  • Reinforce thermal insulation;
  • Ventilate condensate;


  • press-diffusion type -vaporative capacity equal to 300 grams per m2 is used under the roof as an outer layer. Unsuitable material for facade insulation.

  • Diffusion type - throughput from 300 to 1000 grams per m2. Good material for the protection of insulation, roof and walls of the building. Excellent water repellency and airtightness.
  • superdiffusion type - 1000 and more grams per m2. This material is striking in its uniqueness, has the properties of the skin.

    Consists of breathable membranes that allow steam to pass outside and prevent moisture from penetrating inside. This technology is used in the manufacture of clothing and footwear.

Regardless of the type chosen, it is important to properly lay the vapor-permeable membrane.

In case of thermal insulation, the film is laid to remove steam from the outside, and for roofing insulation on top of insulation wool. In the case of roofing work without insulation, the film should be laid at the bottom of the rafters.

When working with ceiling ceilings of rooms, the membrane should be located under a layer of insulation.

How to work

Often when working with a vapor-permeable membrane, the question arises how to distinguish the wrong side from the front? Everything is very simple. Most often, the manufacturer himself indicates the procedure and technology of work.If there are no special instructions, then one should be guided by color, as a rule, the outer side has a much bright coating.

A large assortment of building materials complicates the choice.

It is preferable to choose trusted, high-quality manufacturers - Tyvek, Tekton, Corotop. , Delta, etc.

Among domestic brands, the Izospan A model is especially popular. It is used as a protective agent for walls and roofs. The membrane will be on the outside.

This vapor-permeable membrane is characterized by excellent strength, environmental friendliness and safety characteristics. The main differences are the absence of harmful components, resistance to various bacterial and chemical infections.

Installation is carried out in the following sequence:

  1. How to lay the membrane - inside out or face down? Choice of material - Installation of vapor-permeable film + Photo and Video First carried out installation of a vapor-permeable membrane with an overlap of about 15 centimeters in order not to disturb the air permeability, the joint should be sealed with a special vapor barrier tape. It is not permissible to allow sagging of the film; to avoid this, slats and battens are used.
  2. A vapor-permeable film, except for roofs and walls, is also used for floor coverings.

    The work is carried out in the following sequence: rough stage, waterproofing, insulation layer, vapor barrier and finishing layer. If all the steps are followed consistently, there will be no moisture retention either inside or outside, which guarantees clean indoor air and a long service life of the floor. The most practical option is considered to be the universal Izospan V. It will protect against moisture, mold and mildew.

Building a house is not an easy task, you need to study all the subtleties and features of building codes and technologies.

Construction design should be done by professionals.