Is it possible to use ordinary polyethylene instead of vapor barrier: answering the question

On numerous forums and on social networks, controversy is raging on the topic: is it possible to use plastic wrap instead of a specialized vapor barrier? The construction community in this matter was divided into two camps. Some argue that the film can be used and cite the example of Western experience where this is practiced. Others believe that it is categorically impossible to use polyethylene. Which of them is right - let's figure it out.

What is a vapor barrier for?

Everything is simple here - vapor barrier is needed in order to cut off the enclosing structures and their contents, in particular, insulation, from moisture-saturated vapors inside the room. If, for example, moisture gets into the walls and the insulation becomes damp, then the house will quickly lose its thermal insulation properties, and the frame will begin to rot. So a vapor barrier is an indispensable element of the frame structure.

What do building codes say?

Polyethylene film does not allow steam to pass through, therefore, based on logic and common sense, we can conclude: it is suitable for use as a vapor barrier. And this is also confirmed by the Code of Rules 31-105-2002, in which it is written in black and white that a plastic film with a thickness of at least 0.15 mm can be used as a vapor barrier. This could end the discussion, but there are nuances.

Some "but"

A film with a thickness of over 0.15 mm, of course, can be used as a vapor barrier material, but for this you need to take into account nuances of materials and installation.

• Specialized vapor barrier, unlike conventional film, has a higher tensile strength. This is done so that it can be securely fastened with staples. With this method of installation, ordinary polyethylene can break at the points of fixation of the staples. If you have chosen polyethylene as a vapor barrier, then it should be fixed very carefully. It is especially important to control this process when the construction is carried out by a hired team. If workers make holes, the tightness of the system will be broken and this will lead to wetting of the enclosing structure. With a specialized vapor barrier, such a development is less likely.

• On a professional vapor barrier, one side is fleecy. This is done so that the condensate lingers on the material, and does not flow down to one point. This function allows excess moisture to escape. This is especially important if there is a lot of moisture-saturated steam in the room and ventilation does not work well. When using conventional polyethylene in such conditions, water accumulations can form at the lowest points. And this water will sooner or later penetrate the logs, floors, floor coverings.
• A specialized vapor barrier allows a certain amount of steam to pass through due to diffusion. But this vapor does not cause any damage to the building envelope and is removed by ventilation gaps. This function of a vapor barrier material is necessary when there is a lot of moisture-saturated steam in the room and the ventilation does not have time to remove it.

Output

Polyethylene can be used with confidence as a vapor barrier if two conditions are met:

• the house has high-quality ventilation that can cope with the volume of steam produced (bathrooms, kitchen, bathroom are especially important);
• you are completely confident in the quality of installation and you know for sure that the tightness circuit is not broken anywhere.

Are you for a professional vapor barrier or for an ordinary film? Write your opinion in the comments!

Friends, we are growing and there are already 130 thousand of us! Like, subscribe to the channel, share our life hacks, articles and recipes - we are workingso that you receive only useful and interesting information!

Read also:

• Even the devil is incapable of that! Photo selection of blunders from construction and repair.
• Why buckwheat is not eaten in the USA and Europe: about their dislike for our national cereal.

Watch the video - An energy-efficient two-story house made of gas silicate: the story of an architect from Voronezh.