Vapor barrier for roof: types of materials and efficiency of use

Vapor barrier for roof: types of materials and efficiency of use

Heat preservation is not only component of economy. First of all, this health and comfort. Excess moisture in combination with cold air leads to formation of dampness and mold. To be in the room where the fungus has appeared, not just uncomfortably, but also it is unsafe. Besides it leads to inevitable destruction of building constructions which are under continuous influence of moisture. The modern reliable vapor barrier for roof will help to avoid above-mentioned problems.

What is vapor barrier

Level of dryness, comfort, heat preservation indoors in many respects depends on condition of roof. It is barrier between cold external environment and internal heat of the building. Use of heaters in the absence of waterproofing for roof is ineffective. The waterproofing prevents penetration of steam from premises in insulating layers.

Long time as vapor barrier at the device of roofs the normal polyethylene film was used. But this material is mechanically vulnerable. Besides, it is characterized by rather high level of moisture permeability. The modern vapor barrier film for roof has vapor permeability of 0.4 g/m ², and normal polyethylene – 13-20 g/m ². It is applied to any kinds of roofs: flat, cattle, at the device of the mansard floor. The reliable vapor barrier of ceiling at the cold attic is especially important.

Vapor barrier is one of components of “roofing pie” which also the waterproofing and heater enters.

If “pie” is laid correctly and from quality materials, then the main functions of vapor barrier can be considered:

  • preservation of microclimate, ensuring air exchange, maintenance of optimum temperature condition and level of humidity in rooms of the building;
  • protection of roof design against moisture penetration outside and couple from within, prevention of formation of condensate, damages, fungus, mold;
  • decrease in heatlosses in cold season that promotes economy of costs of heat carriers;
  • increase in fire resistance of designs of roof;
  • reduction of repair costs of roof and building.

The lack of implementation at least of one of above-mentioned functions speaks about bad quality of film or about the mistakes made at its laying.

Helpful advice! Before acquisition vapor barrier of material it is necessary (in the absence of knowledge) to consult with the experienced roofer. The wrong choice can lead to damage by steam of thermal insulation material.

Types of vapor barrier and their feature

Modern the vapor barrier of film, actively forcing out plain polyethylene, roofing material, paper roof covering, differ in the wide range and assignment.

The following types are most widespread, available at the price and mounting mode:

  • standard vapor barrier film. It does not allow to be formed to condensate on roof and heater;
  • the foiled vapor barrier. Unlike standard layer possesses the reflecting function and provides the raised vapor barrier and also reflects and returns some part of heat to the room;
  • membrane film. Has effect of isolation and limited vapor permeability that allows to control removal of excess humidity from the room.

The vapor barrier film can be made of polyethylene or polypropylene. Polyethylene – material fragile therefore the polyethylene product is reinforced special fabric or mesh reinforcement. Polypropylene films represent the woven material on both sides laminated by the thinnest polypropylene. This type of product differs in durability, resistance to influence of ultraviolet.

There are options when the antioxidant layer which absorbs and holds moisture is applied on polypropylene film, and after the termination of intake of steam the layer dries by means of ventilation. The device of vapor barrier of this kind allows to stack only in its one way: the rough antioxidant layer is placed below, smooth surface – above.

The films laminated on the one hand by the foiled layer differ in the highest qualities of vapor impermeability and are the most suitable type of vapor barrier for ceiling of rooms with the increased humidity (baths, saunas, pools, etc.).

Kinds of membrane films

Special type of vapor barrier are subroofing membranes. It is material, strong, resistant to temperature drop. It does not differ in low vapor permeability, but is effective at construction of separate types of roofs. It is characterized by more complex structure, than normal film. Time of membrane reminds microscopic funnels. Thanks to this property it does not miss couples from outer side, but perfectly takes away moisture from internal.

Now several types of subroofing membranes are issued:

  1. Perforated membrane. It is the reinforced film or the combined fabric having chipped openings. It is used for arrangement of cold inclined roof. It cannot be applied to heater vapor barrier. In freezing weather of couples can settle on inside face of membrane.
  2. Porous membrane. Has set of interfiber time for passing between them water vapor. The vapor permeability of material can be different, it depends on the size of time and degree of hydrophily of their walls. It is not recommended to use this type of vapor barrier in the conditions of high dust content. In dry and windy weather dust through gaps can accumulate on membrane and close time.
  3. Three-layer superdiffusion membranes. Are made of several layers. They have no openings into which dust or moisture can get that is considerable advantage. Membranes do not lose high vapor permeability in the dusty environment. Also It should be noted their excellent wind-shelter ability.
  4. Two-layer film membranes. The reduced the price option of sandwich product. The lack of one of protective layers considerably worsens reliability.

Vapor barrier materials have to be elastic, strong and convenient in work. When fastening by dowels, self-tapping screws, brackets, nails it is necessary that they did not seek, but at the same time densely adjoined to fastening.

Helpful advice! When choosing vapor barrier of material it is necessary to pay special attention to quality as it is base layer of roof design and its repair it is almost impossible.

Bases of right choice

At arrangement of roof it is important not only the nobility as it is correct to stack vapor barrier, but also how to decide on the necessary material. It is required to consider when choosing, first of all, type of roofing material.

If the flooring of roof is going to be made from materials of low heat conductivity: slate, tile – it is necessary to use diffusion vapor barrier of membrane.

Roofs from metal tile, professional flooring roof (connection of sheets by means of seam) are recommended to be protected, using vapor-tight film with anti-condensate layer.

When choosing vapor barrier of materials it is necessary to consider the following parameters:

  • vapor permeability;
  • durability of functioning;
  • features of mounting;
  • cost.

Level of vapor permeability is measured in gr/m ² per day. The permeability is less, the heater, finishing, structural components of roof are protected from soaking more reliably. To some extent the film has to provide air exchange, otherwise greenhouse effect for the room will be created. Anti-condensate polypropylene films and the “breathing” diffusion membranes provide optimum vapor barrier.

The durability vapor barrier of materials is caused by number of qualities:

  • tensile strength and gap;
  • resistance to high temperatures;
  • not exposure to influence of ultraviolet.

The budgetary polyethylene film can be torn already when mounting and collapse from temperature changes. Differ in durability vapor barrier of membrane from nonwoven artificial fibers with protective layer. They are steady against mechanical damages and influence of temperatures.

Features of mounting should be known before purchase of film as correctly it is possible to calculate quantity only if to know the size of overlaps. Also purchase of the accompanying materials directly depends on way of laying. If the adhesion vapor barrier of material to mounting adhesive tape low, then inevitably leads afterwards it to violation of tightness vapor barrier of layer. Therefore, it is necessary to take other form of adhesive tape.

The vapor barrier price for roof directly depends on its quality. The budgetary options are short-lived. It is necessary to be able to calculate the material cost correctly. The low price for roll can not mean optimum cost, and be consequence of small metric area. Only comparison of the price for 1 m ² different types of vapor barrier will help to make right choice.

Helpful advice! The quality of film has to correspond to quality of roofing material. If material is expected long operation, and period of validity of vapor barrier is less, when replacing it is necessary to sort all “roofing pie”.

Sequence of laying of vapor barrier: basic rules

The vapor barrier happens two types: rolled and sheet.

Mounting of rolled laying is made as follows:

  • material is rolled;
  • measure the necessary length of cloths and have them with pad (100–200 mm) on the next fragments;
  • fix brackets or wooden rails;
  • places of joints and overlaps fix by adhesive tape for vapor barrier (or other adhesive tape).

Sheet mounting demands preliminary creation of wood furring or framework from profile which the waterproofing will keep within. It is possible to fix by self-tapping screws or the stapler (according to material).

When laying “roofing pie” question: “What party to stack vapor barrier?” – arises among the first. The film of difficulties, identical from two parties, when laying does not cause: what party put vapor barrier – the effect will be identical. The film having two-layer structure, where one party smooth, and the second rough (for condensate deduction) is placed the smooth party outside (adjoins to heater), and rough – in the room.

What party to stack the vapor barrier foiled to heater, to define also simply. As this type of vapor barrier is intended not only for blocking of vapors of moisture, but also for deduction of heat, the reflecting party (foil) has to be directed inside, to the room.

The membrane vapor barrier can be double-sided, and then for its efficiency not very well what party to heater the vapor barrier of this look is located. If the membrane vapor barrier one-sided, the producer surely designates inner side.

Vapor barrier for roof: types of materials and efficiency of use

Basic rules of laying of vapor barrier:

  • cleaning and drying of covering;
  • the vapor barrier film has to be mounted without saggings, with small tension;
  • the ventilation system is necessary for the correct functioning;
  • the tightness of joints is obligatory.

Helpful advice! Upon purchase of waterproofing it is necessary to study the instruction (summary). Sometimes it is required not one, but two ventilating blowing.

As it is correct to stack vapor barrier for roof

Mounting of vapor barrier of roof – process which complexity depends on roof type.

Than intricate the rafter design and, respectively, roof form, especially expensive and difficult becomes problem of high-quality isolation. Hydrovapor barrier for roof it is necessary to install from within.

Laying of cloths can be carried out vertically and horizontally. If the horizontal way is chosen, then to begin to mount it is necessary from above. Each subsequent cloth keeps within on previous with overlap not less than 10 cm. Seams are pressurized by means of adhesive tape. It is possible to use adhesive tape one-sided, it is imposed from above. The double-sided adhesive tape is put inside.

If mounting of vapor barrier for roof is carried out along feet of a rafter, i.e. vertically, then the overlap of cloths should be done on wooden rafters. To wooden constructive parts the vapor barrier material fastens brackets or galvanized nails. It is desirable to strengthen places of gluing of joints clamping levels which it is especially important to use on roofs with bias to 30 degrees and at the small density of heater.

Helpful advice! The used wooden levels and bars need to be processed anti-septic tank. It considerably will prolong the term of their full operation.

If the design has dormer-windows, hatches or other passes through roof, then on their perimeter it is necessary to paste butyl – rubber self-adhesive tape which will exclude passing of moisture and steam, strongly pressurizes places of cut in vapor barrier to film even if they adjoin not absolutely plain surface. At tape of this type high water-repellent properties and good resistance to temperature influences. Besides it easily levels roughnesses.

If through roof there pass ventilation pipes, then the film needs to be turned and to envelop densely around them, having strongly fixed by one-sided adhesive tape.

The mistakes made in the course of laying of vapor barrier

In the absence of experience and professional consultation when laying vapor barrier number of mistakes which considerably will affect afterwards efficiency of functioning of vapor barrier is made.

The most widespread of them:

  • leaky adjunction of film to runs, crossbars, endovy, to beams;
  • ignorance what party to put vapor barrier to heater;
  • use for sealing of narrow adhesive tapes (up to 50 mm);
  • when sealing apertures the deformation stock of film (20–30 mm) is not left;
  • the polyethylene product around dormer-windows is not closed from inside owing to what after a while it collapses under the influence of ultraviolet and low temperatures;
  • the film bends around feet of a rafter. Moisture will get into gap between rafters and vapor barrier;
  • in places of adjunction of film to much uneven surfaces special glue is not used. Construction adhesive tape, butyl and other types of adhesive tapes of full tightness in such cases do not provide.

Helpful advice! When laying vapor barrier you should not neglect even the seeming insignificant rule or to break the sequence of mounting. The good result will be achieved only at observance of all requirements.

Vapor barrier for ceiling in wooden overlapping

Wood – material organic therefore misses evaporations. But also for it excessive moistening steam is undesirable as under its influence the tree extends, can rot. That ceiling overlapping which is under the cold attic remained in the normal state, it is necessary to arrange the correct vapor barrier. Here it is important to observe the sequence of laying. The first place the component having the minimum vapor barrier. It has to be zero or close to zero. The following layers – with permeability above previous.

From the room the vapor barrier has to look as follows:

  • vapor barrier. Polyethylene or polypropylene film, diffusion membrane. Keeps within from above on overlapping;
  • heat insulation. Rolled, filling or tiled material. Fills emptiness between floor beams;
  • waterproofing. Layer from diffusion membrane or perforated polyethylene. Keeps within only in case of use of the attic.

If attic-floor room it is not going to use, then the layer of waterproofing is transferred under slopes where it carries out protection of all roof.

Laying vapor barrier of material on wooden overlappings is made with rounding of each beam. Strips are mounted perpendicular to beams. Material in this case does not stretch, small saggings are obligatory.

At panel board wooden overlapping each compartment is wrapped. Material is found according to the sizes of board and height of walls.

Helpful advice! It is not necessary to rewind rolled vapor barrier material not to mix the party which has to adjoin to overlapping (it is specified by the producer).

Vapor barrier for bath

Bath – the room which demands high temperature and is characterized by the big level of humidity. The vapor barrier of this building is applied to heater preservation and also to protection of wood structures against moisture influence. When choosing vapor barrier materials it is necessary to consider that for rooms different for designated purpose it is reasonable to use different isolation:

  • for sweating room optimal variant – the foiled vapor barrier reflecting heat and creating additional effect of thermos;
  • shower it is possible to isolate polyethylene or polypropylene film;
  • in the waiting room and the restroom the membrane vapor barrier which will provide necessary air exchange will be appropriate.

The bilateral structure of material allows to use actively it for vapor barrier in rooms of baths. How to stack vapor barrier and what party to fix vapor barrier, prompts availability of different structure of the parties: the rough surface is intended for steam absorption, therefore, it also has to be directed in the room.

Whether the vapor barrier when warming is necessary mineral wool

Mineralno wadded heater – effective type of heat insulation which is actively applied in modern construction. But it has one rather essential shortcoming: when soaking mineral wool collapses and loses heat-insulating properties. For this reason use of film of vapor barrier, along with this heater, is extremely necessary. She will create barrier which will allow to protect heat insulation layer from influence of steam and will give the chance to keep heat of rooms.

What party to put vapor barrier if mineral wool as heater is used?

If the double-emulsion film with the moisture absorbing layer is applied, it has to be directed to the room from where steam flows rise. The smooth party adjoins heater. When using material with foil surface, the aluminum covering will become barrier to moisture penetration in heat-insulating material. Therefore, this surface also has to be directed to the room.

Helpful advice! If mineral wool is applied to warming of rooms with the high level of humidity, then it is more reliable to use vapor barrier with foil layer as it has the lowest level of vapor permeability.

Prices and producers

Vapor barrier of Juta – products of the European producer which differ in the variety satisfying the different purposes when mounting vapor barrier. For convenience of the buyer easily to differentiate material, not to confuse waterproofing, wind insulation and vapor barrier, they have the names Jutakon, Jutavek and Jutafol (respectively). In addition to standard types of product, this Czech company releases Jutafol H110 film with the self-fading reagent which reduces inflammability level to minimum. Reduction in cost of products due to simplicity of packaging – the successful decision of the company.

Vapor barrier of Axton – products of the French company Leroy Merlin. It has three appearance: In, With and D. Axton In – polyethylene film, the budgetary option. Will serve considerable time if to avoid mechanical damages and it is correct to fix, using not the stapler, but special nails with wide hats. This material is applied only to internal mounting.

Axton C – polypropylene product, stronger, universal. Has different indicators of permeability. It is two-layer material, it is recommended for the warmed and not warmed types of the roofs having various designs. Axton D resembles tent superficially. It is used for water isolation and vapor barrier. It is characterized by high strength, ease of mounting. Products of this company are distinguished by the high level of environmental friendliness.

Vapor barrier the materials Tyvek are manufactured at the plant in Luxembourg. In basis – quality polyethylene, nonwoven structure. The main difference of products – environmental friendliness and the “breathing” membranes created on the innovation technologies with controlled vapor permeability. The price of vapor barrier of Tyvek is 7-10 percent higher, than the cost of analogs.

The vapor barrier price for ceiling most of all depends on quality of material, its density and the producer. For this reason branded products of the foreign companies differ in higher cost.

Vapor barrier for roof: modern solution of moisture protection

Roof – building element which maintains constant double load. From outer end it is subject to influence of the atmospheric phenomena: rainfall, sunlight, low temperatures, wind. From the inside she experiences internal influence of temperatures and humidity. In such conditions to revaluate need of the correct device of vapor barrier which lack can lead to destruction of roof and afterwards the building it is just impossible.

Modern technologies have allowed to create from film polymers which are capable to provide vapor barrier of necessary level. Wide choice of material allows to apply it according to conditions and purpose. Having attentively studied as it is correct to put vapor barrier, fulfilling all specifications, it is possible to create healthy microclimate in rooms and to provide to the building in general for many years existence without serious repair work, keeping esthetic exterior.

The price the vapor barrier for roof for m ² is not present the bases to consider high that it makes material available to any builder.

To carry out reasonable and rational material selection, it is correct to make mounting of vapor barrier – desire of each house owner. The contents of article are designed to help to execute the vapor barrier installation independently. But even if such decision is unacceptable, it is necessary to be informed correctly to evaluate the expenses and quality of work of the employed specialists.

Like this post? Please share to your friends:
Leave a Reply