No Complication for the Vapor Barrier Installation

Installation of vapor barrier is required during the construction of residential buildings: the membrane protects the insulation from vapors emanating from the room inside the roofing space; on the other hand, the vapor barrier film prevents condensate from entering the room. Improper installation of the membrane (the wrong side) is fraught with the accumulation of an excessive amount of vapor inside the room, as well as uncontrolled access of moisture directly under the roof. Insulation gradually soaked with water and cease to perform its functions, and the material of the sheathing and roofing will undergo intensive destruction.

Which side to mount vapor barrier

Special materials for vapor insulation are produced in the form of single-layer films, foamed polyethylene with metallized coating and two-layer membranes. Their installation has some differences, which is why it is not easy to figure out which side to attach the vapor barrier:

Polypropylene film is installed with a rough surface to the under-roof space. Such an insulation texture will collect moisture, which will evaporate through the ventilation gap. However, its value must be at least 20 mm. If the film is the most common (polyethylene), its sides will be identical.With the Vapor barrier installation this really important.

  • The two-layer membrane is laid with a smooth side to the insulation. For ease of use, manufacturers often put on the wrong side of the fabric special marking.
  • One-sided laminated polypropylene is also guided by a smooth surface to the insulation.
  • The foil side of the special film is turned to the insulation.
  • Given the variety of vapor barrier materials in the construction market, it is difficult to compile a comprehensive guide to their installation. Detailed information is usually contained in the instructions supplied by the manufacturers. But still, there are two more general rules:
  • If the instruction is obscure, and the film is painted in different colors, the lightest tone should be turned to the insulation.
  • Many materials are rolled up in a roll so that the side that turned down when it is rolled out can be immediately laid on the thermal insulation.

The main stages of installation

For the pitched roof there is a certain sequence according to which a high-quality vapor barrier is established. It is mounted after laying the insulation, on the surface of which there must be no defects. Bars for lathing are treated with antifungal compounds, after which a pre-calculated amount of film is prepared (covered area +15%) and the following:

  • construction stapler;
  • special double-sided tape for insulating and fastening cloths;
  • construction knife / clerical;
  • self-tapping screws;
  • roulette;
  • unilateral adhesive tape for joints, defects and cracks (of the same manufacturer);
  • screwdriver;
  • pencil;
  • scissors.

On the rafters, between which the insulating plates are laid, fill the bottom of the sheathing of the two boards. Stick a strip of special tape with two adhesive sides. Cut the roll into webs of appropriate length. Then, starting from the bottom of the crate, lay the membrane horizontally by marking up on the insulation, slightly pulling the cloth.

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