Installation of vapor barrier on the roof - installation
It seems to people uninformed in construction that installing a vapor barrier on the roof of a residential building is excessive care and reinsurance, which results only in additional costs. However, every experienced roofing master will confirm that a properly selected waterproofing film significantly increases the service life of the roofing, as well as improves the microclimate in the attic or attic room. In this article, we will describe how to choose independently the water and vapor insulation for the roof, as well as the process of laying the material on the rafter frame.
Definition and functions
Vapor barrier film - a special material that is necessarily included in the composition of the roofing pie of the roof, which has a pronounced vapor-blocking effect. According to the well-known law of convection, the warmer and more humid air, abundantly released in the process of people's life, rises up into the under-roof space, then it settles in the form of condensate on the roof frame of the roof, leading to dampening of the insulation and wooden elements of the structure. The vapor barrier film in the roof has the following functions:
- Preservation of operational qualities of a heater. Installation of vapor barrier prevents the accumulation of condensate inside the insulating material, which significantly reduces the effectiveness of insulation.
- Extending the life of the roofing. Roofing materials are much better protected from moisture and corrosion from the outside. Installation of vapor barrier solves the problem of condensate exposure to the bottom surface of the roof covering.
- Protection of a wooden frame of a roof against rotting. Properly mounted, vapor barrier film prevents the roof rafters from getting wet from the effects of condensate, which causes wood to rot.
Note! The vapor-blocking film “works” effectively only if it is correctly selected for the climatic conditions, the roof construction, and the type of roofing material. An improper vapor barrier not only does not benefit, but also enhances the process of condensation.
Material Requirements
The most primitive and cheap material for the vapor barrier of the roof is glassine. But in modern realities, the installation of this outdated canvas is practically not performed, since there are more efficient and durable analogues. The actual vapor barrier is made of high-strength polymers with improved performance characteristics. Properly selected vapor-blocking film has the following qualities:
- Wide temperature range. To make installation possible in any climatic conditions, the film must withstand high, low temperatures and even their sudden drops. The optimal temperature range for products of this type is considered to be the interval between -70 and +100 degrees.
- High vapor permeability. The lower the vapor barrier is, the better. Previously, laying of polyethylene films with vapor permeability of 13-20 g / m2 was carried out, and now polypropylene analogs are used for the arrangement of the roof, allowing no more than 0.4 g / m2 to pass through.
- Long service life. Installation of the vapor barrier, the service life of which does not exceed 10 years, is inexpedient, since modern roofing materials serve more than 20-25 years, and it is almost impossible to replace the film without disassembling the structure.
- Elasticity. Vapor-blocking film based on resistant polymers has a high elasticity, which simplifies the installation of the material, and also reduces the amount of damage during installation.
Important! Experienced craftsmen believe that the main indicator of the quality of vapor barriers is the high strength properties of the material. Correctly mounted paroblokiruyuschuyu fabric can withstand even the weight of snow, rainwater or melt water with extensive damage to the roof.
Types of materials
Steam-blocking film is a special material, it does not allow saturated, heated air, which leads to the formation of condensate, wet insulation, as well as the destruction of the frame under the roof. It is a thin, lightweight, but very durable and UV-resistant fabric based on thermoplastic polymers. There are the following types of materials for vapor barrier:
- Polyethylene. Polyethylene is a fairly thin, lightweight and at the same time cheap polymer that is used to make vapor-blocking membranes. However, the strength properties of such a film are low, so it is reinforced with a special mesh or cloth. Installation of laminated polyethylene vapor barrier is performed in saunas, baths and other rooms where it is necessary to keep warm.
- Propylene. Vapor-blocking membranes based on propylene are characterized by increased strength, resistance to ultraviolet radiation, and low vapor-carrying capacity. They are a woven material with an anti-condensate layer.
Consider that perforated materials are not allowed to organize roof insulation of the roof. It is important to properly select the vapor blocking membrane in order to protect the roofs from the negative effects of condensate.
Technology use
Laying the vapor barrier material is an important technological operation performed in the process of roofing, the quality of which depends on its reliability, durability and durability. Installation of vapor barriers is carried out from the inside of the attic room after the roof truss frame is ready in compliance with the following rules:
- Vapor-blocking fabric can be laid along or across the truss legs of the frame.
- Be sure to start laying from the ridge of the roof, placing the strip material overlap with overlapping 10-15 cm.
- The material is fixed using staples of a construction stapler or galvanized nails.
- The joints between the strips are hermetically connected using special adhesive strips located along the edges of the canvas.
- After mounting the waterproofing along the rafters, the glazing bead treated with an antiseptic is nailed so that the skin does not touch the membrane.
Important! Vapor-blocking film has two sides, which differ in the nature of the surface and properties. During installation, the fabric should have a rough anti-condensate side down.
