Plastic windows are one of the most frequently used window systems today, with advantages such as comparatively low acquisition costs, weather resistance, low maintenance and design diversity. Especially in residential and commercial construction, they have by far the largest market share in Germany. A variant of the PVC window is the so-called PVC-aluminium window, which is equipped with an additional aluminium shell on the outside. This protects the actual window profile and allows even more design freedom in the choice of colour and décor.
The profiles of PVC windows are made of polyvinyl chloride (PVC), a thermoplastic that can be easily shaped under the influence of heat and pressure. Injection moulding and extrusion processes thus enable a wide range of profile shapes, from edge-rounded to straight. To reinforce the frames and sashes, most plastic windows contain internal frames made of steel or aluminium profiles. The formation of several air-filled chambers in the profile cross-section, usually 5-7, ensures good thermal insulation properties. The higher the number of chambers, the better the insulation value (uf) of a window profile. Another important criterion for the insulating effect of a window profile is the so-called construction depth, i.e. the thickness of the window profile. For current window products, this is between approx. 65 mm and 105 mm.
With the help of externally applied foils or plastic layers, different structures and colours can be achieved. The quality of the window depends largely on the quality of the plastic profile used. High-quality plastics are easy to clean, weather-resistant, UV-resistant, acid- and alkaline-resistant and insensitive to exhaust fumes and cleaning agents.
RAL quality mark: Window profiles can be awarded the so-called RAL quality mark. This means that they are monitored in accordance with the RAL-GZ 716/1 guideline of the Gütegemeinschaft Kunststoff-Fensterprofilsysteme e.V. with regard to weather resistance, appearance, dimensional accuracy, behaviour in cold/heat, impact resistance and fire behaviour. The user can therefore be sure that all window components that have been awarded the so-called RAL quality mark are subject to regular quality monitoring.
Thermal insulation: The thermal insulation value of a window uw (w for window) is calculated in accordance with DIN EN ISO 10077-1 from the following three individual values:
The values given by the manufacturers usually refer to a standard window measuring 123 cm x 148 cm. However, since the frame and glass with their different insulation values are in different ratios depending on the proportion and size of a specific window, the actual values deviate from the standard values, so that the Uw value can be calculated individually for each window on the property. The manufacturers take care of this service on request. As a rule, small windows have a higher and thus worse uw value overall due to the relatively worse insulation value of the frame . Windows with a small proportion of frames, i.e. large windows, have a better overall insulation value, etc. Important parameters that influence the insulation value of the window frame (uf ) are above all the construction depth and the number of hollow chambers.
Sound insulation: The protection of a room against external noise is becoming more and more important in our living environment. The sound-insulating quality of the outer wall of a room depends largely on the sound insulation level of the windows, as they are usually significantly weaker than the surrounding wall, regardless of the wall construction. There are different sets of rules for the assessment of the required assessed sound insulation level R'w of windows, some of which also lead to different results. The planner must therefore decide according to which of the following regulations he works or whether he carries out several assessments:
VDI 2719 and DIN 4109 are most frequently used in practice.
Wind resistance, driving rain tightness and air permeability: In addition to their visual differences such as profile shape, colour and surface or the heat and sound insulation values already described, windows are also differentiated according to the following properties, which the planner must evaluate or specify:
These three quality characteristics depend on each other and can also be determined on the basis of the guideline FE-05/2 prepared by ift-Rosenheim. The classification is based on the wind load zone, the installation height and the terrain category.
Burglary protection: The classification and evaluation of the burglary resistance of door elements, windows, curtain walls, lattice elements and closures is regulated in the European standard DIN EN 1627, which distinguishes between 7 different RC classes (RC for resistance-class). In addition to the actual constructions (windows, doors, etc.), their locks, locking cylinders, security fittings and fillings (e.g. glazing) are also tested for the classification into the various classes. This means that a component only corresponds to a certain RC class if all these associated components have been tested accordingly. As can be seen from the RC classes described, the production of completely burglar-proof components is not possible. The aim of the security features is therefore to increase the duration, risk and resistance of burglary in such a way that a potential perpetrator refrains from attempting to break in. In the event of increased security requirements, additional measures should therefore be taken, e.g. alarm protection systems, motion detectors, etc.
Installation situation: The connection of the windows to the shell wall should be carried out in accordance with the specifications of the thermal bridge catalogue of DIN 4108 Supplement 2. If a different installation situation is planned, either a proof of equivalence according to DIN 4108 Supplement 2 or a thermal bridge calculation according to DIN EN ISO 10211-1 must be prepared to ensure that no moisture and thermal weaknesses arise.
The correct position of a window in relation to the reveal depth, also known as window recess, depends on the wall structure. Among other things, the isothermal course is decisive for the assessment. This can be calculated (also by the manufacturers) and ensures that no moisture and heat defects occur. If arranged incorrectly, condensation can form on the inner window loave. The following window recesses have proven their worth:
Frame insulation: Even in the most modern design, windows are a thermal weak point in the building. Within the window element, the frames and sash profiles usually have a worse U-value than the panes. By insulating the frames, heat loss is reduced and the window frames look slimmer and more modern. However, the installation of roller shutter rails or parapet railings must be carefully planned in detail, these may have to be installed before the insulation is carried out.
Dimensional specifications: Unlike doors, windows are not prefabricated in standard dimensions, but are manufactured according to plans or measurements for each object. However, product-related maximum specifications of the manufacturers must be observed, e.g. patio doors with plastic windows can be manufactured at a maximum of 1.10 m to 1.20 m. The height and element width are also limited and the length/width ratio (e.g. in the case of horizontal windows) must be checked with regard to the load-bearing capacity of the fittings. Early coordination with the manufacturer is therefore advisable.
Surfaces and colours: PVC windows are always white in the original version. For a relatively small surcharge, however, various color and texture options are available. The most common variant is to apply a plastic film to the profiles in the industrial process during the production of the window. In this way, in addition to different colours, wood décor foils or other effect surfaces are also possible. Some manufacturers offer profiles with acrylic surfaces for colouring. This acrylic layer is melted onto the PVC window profiles during production and is very weather-resistant. When using aluminium cover shells, the RAL and DB colour palettes are also available, so that in addition to the increased weather resistance, the extended design possibilities also speak in favour of PVC-aluminium systems.
Installation: Windows can be attached to the reveal in different ways. In the case of solid walls, windows are usually screwed directly through the frame into the masonry. Alternatively, chattering can be used for assembly. In the case of the so-called pre-wall installation, brackets must be attached to the outside of the shell wall. After the windows have been fastened and before the waterproofing has been applied, the connection joint must be insulated. This is usually done by foaming or by using pre-compressed, heat- and sound-insulating sealing tapes.
Sealing: Windows must be installed and sealed in accordance with the "Generally Accepted Rules of Technology". The implementation of these installation specifications is also incorrectly called RAL installation and is anchored in various detailed variants in the "Guidelines for the Planning and Execution of the Installation of Windows and Front Doors (March 2010)", published by the "Gütegemeinschaft Fenster und Haustüren e.V.". With regard to waterproofing, the principle applies that the connection joint must be tighter on the inside than on the outside, so that moisture entering through vapour diffusion can dry to the outside. One of the most common variants is sealing with sealing tapes or compression tapes. However, sealants such as silicone or acrylic are also permissible for waterproofing under certain circumstances and are often used in renovation measures. In the case of windows in the splash water area, a seal must also be installed on the outside to prevent direct use of splash water. This is often done with EPDM tapes or liquid waterproofing.
Preparation of the reveals: The window sealing in new buildings is usually made with sealing tapes. Before the windows are installed, a dust-free and smooth design of the reveal must be ensured in order to ensure the adhesion of the sealing tapes. In the case of masonry, a smooth line of cement slurry must be produced for this purpose or care must be taken to ensure that only smooth masonry stones (beginner's stones) are used in the reveal.
Weather conditions: The installation of windows is generally possible even at sub-zero temperatures, but clear specifications for installation apply to waterproofing materials such as sealing tapes or sealants. As a rule, sealing tapes cannot be installed below +5°C. However, special products are also available for processing down to -5°C if required.
Blower door test: To check the tightness, a blower door test is strongly recommended before completion of the building or is often specified by the thermal insulation certificate.
Recycling: Plastic windows can be recycled, they are usually no longer disposed of. This recycling activity is carried out by suitably qualified companies.
DIN 4108, Supplement 2, Thermal insulation and energy saving in buildings, thermal bridges, planning and execution examples
DIN 18055, windows; Joint permeability, driving rain tightness and mechanical stress
DIN EN 12207, windows and doors; Air permeability
DIN EN 12208, windows and doors; Driving rain tightness
DIN EN 12210, windows and doors; Resistance to wind load
DIN EN 12608, profiles made of plasticizer-free polyvinyl chloride (PVC-U) for the production of windows and doors - classification, requirements and test methods.
DIN EN 14351-1, Windows and doors - Product standard, performance characteristics - Part 1: Windows and external doors without fire protection and/or smoke tightness properties.
DIN EN ISO 10077-1, Thermal performance of windows, doors and shutters, Calculation of the heat transfer coefficient
Energy Saving Ordinance (EnEV) - Ordinance on Energy-Saving Thermal Insulation and Energy-Saving System Technology for Buildings
Guideline TBDK of the Quality Association for Locks and Fittings e.V., Fastening of load-bearing fittings of Tilt&Turn and Tilt Fittings with definitions of Tilt&Turn Fittings.
ift guideline FE-13/1: Suitability of PVC window profiles
► Guidelines for the use and tendering of windows and external doors in accordance with the product standard DIN EN 14351-1 – CE marking/ system testing/ minimum requirements, published by the Test Centre for Building Elements (PfB). (PDF)
► RAL-Gütegemeinschaft Kunststoff-Fensterprofilsysteme e.V.
► ift Rosenheim, Institut für Fenstertechnik e.V.
► Würth, window installation, applications, solutions and products according to the state of the art (pdf)
► The required sound insulation level of soundproof windows: A comparison of different regulations, Bavarian State Office for the Environment (pdf)
Source: bauwion
