The use of films in the construction process is often underestimated during the planning stage of a new building. However, properly selected and installed films can provide the house with extra security against excessive accumulation of moisture and help to retain heat. Nowadays, when there are several types of films with different features available, the proper use of films for the construction of buildings provides an opportunity not only to prolong their service life, but also make savings on heating expense.

Polyethylene films for different use.

Diffuser membranes combine the properties of several films and as such they can be regarded combined films. As a waterproof material, these membranes protect heat insulation and constructions from water, at the same time functioning as wind insulation protecting from energy loss due to wind. The structure of membrane allows water vapour to move freely to the outside, but prevents moisture from entering the heat insulation from the outside, thus ensuring efficiency. All diffuser membranes can be used as wind barrier films. Diffuser membranes are laid close to the heat insulation layer leaving 10 – 15 cm overlaps.

Vapour insulation films or vapour barriers are the simplest and most commonly used construction films. They are impervious to water vapour in both directions (exterior – interior or vice versa) and are considered non-breathable films. Still, this insulation provides protection against moisture, protecting the insulation material and building constructions. The vapour barrier is designed for insulating roofs, walls and floors. UV-stabilized 200 microns thick polyethylene film. The material is stabilized against natural deterioration and ultraviolet radiation. 10cm-15cm overlaps should be taped or fused.

Anti-condensate films are applied in pitched ventilated roof constructions for waterproofing purposes under metal surfaces, tiles or slate. Anti-condensate films are particularly recommended under metal roofs where condensate is actively forming. It should be noted that anti-condensate films are practically unable to transmit vapour. Anti-condensate films are composed of several layers. The upper surface is laminated, but the lower surface has coarse texture allowing to absorb a certain amount of condensed water and preventing it from dripping downwards, until it dries out due to ventilation. When installing the waterproof or anti-condensate film in roof constructions, an air gap of approximately 5 cm must be left both above and below the film. These films should never be laid close to mineral wool heat insulation.

The main task of wind insulation to ensure optimal conditions for heat insulation material and external constructions of the building. The main functions of wind insulation films are the protection of heat insulation layer against air and moisture, as well as provision of one-way movement of water vapour from the inside to the outside. Therefore, wind barrier films should have a high level of vapour transmission. The wind insulation film is installed from the outside, close to the insulation material (without a gap) leaving 10 – 15 cm overlaps which should be bonded using specially designed adhesive tapes. Above the wind insulation, ventilation gaps must be left of no less than 5 cm for roofs and no less than 2 cm for external walls.