Quality Triple Glazed German Composite Windows
German composite windows are the next generation of window product. They feature a highly durable surface on the outside and an attractive, more decorative surface on the inside. Composite often refers the product being made of two distinct materials: aluminium on the outside and wood on the inside.
Windows of this construction now represent over a quarter of all windows sold in the UK. Each year, this share is growing as the popularity of UPVC and wooden windows dwindle – in favour of this next generation of products.
Why are German Windows worth a look? They are not the cheapest option. But, if you are looking for quality, performance, function and durability they are quite exceptional.
UK Building Standards VS German
Many people, building their homes in this country, design their project to be built better than the standards required by UK Building Regulations. This is often due to the long term financial and lifestyle benefit from doing so. Essentially, low energy consumption and low (or zero) maintenance are all part of building with energy efficiency in mind.
Large volume house builders have lobbied against higher building standards: claiming that they are not equipped to construct the number of properties required by the government and, at the same time, build to higher standards frequently proposed. In reality, this is probably true. But is a convenient excuse to allow them to maximise profits from lowest possible construction costs.
Custom and Self Builders therefore often look to adopt the higher standards found in countries like Germany and Switzerland – where the building industry is often considered more professional and organised; Passiv Haus and Minergie P as examples. To achieve these standards, they also look to use higher quality products.
Let’s take a look at how these products make a huge difference to a building. Most importantly, if you are looking for a product that is in a home you intend to stay in for a long time, these products are well worth a look.
Firstly, quality German composite windows use a dense, slow grown timber using the finest available grades of wood on the visible faces.
2. Internal Face Timber
Secondly, a defect free face, that uses NO finger joints and that is knot free, is a good feature to look for. It is a likely indication of quality. Many window companies use finger jointing and tolerate minor knots in the timber faces as they know this will not be visible on installation. Often this will “bleed” through the paint finish after 12 months. Most German made products will not tolerate either feature on the visible faces of timber. Many sales people will skirt around the subject: knowing full well that their product is made using a lower cost of manufacture. Look for products that guarantee these features.
3. Timber Engineering
Thirdly, frame construction is also another important area to look at closely. Not all engineered timbers are equal. For instance, most quality German products will use six laminations – with grains all in opposing directions to allow the natural material to provide the window with exceptional stability. Frames are much less likely to warp and twist with the opposing effects of wind and rain in the winter and sun exposure in the summer. Window frames built using well-engineered materials don’t twist; don’t become difficult to open in the winter; and glazing units are much less likely to mist up.
Most importantly, ask what grade of timber is used in the manufacture of the units. A slow grown timber is best.
4. Seals and Airtightness
Significantly, this feature is critical and is where most cheaper windows fall well short of higher German Standards.
In the image below, you can see four levels of seals installed in one of the tilt and turn anthracite German Composite windows. This quality is manufactured by Jomue Fenster of Trier Germany. It has an outer weather seal of butyl rubber which, as a material, has astounding durability and won’t perish. Furthermore, these windows shut like a bank vault which, in turn, delivers the airtightness necessary to achieve the high German standards.
5. Aluminium Screens
Composite windows are effectively wooden windows with maintenance free aluminium exteriors. Aluminium has high durability, particularly when powder coated. German factories weld, polish and powdercoat corner mitres to deliver improved product life expectancy. Look for this important mark of quality. A vast majority of aluminium windows in the UK market are made with mitred corner joints which are NOT welded. And, over time, these are much more likely to show corrosion at the corner joints. They are also much less rigid than the welded types.
Another critical area contains window hinges, handles, locking mechanisms and running gear. These moving parts, if made from quality materials, will keep the frame and the opener of the window in the correct place for many years and also provide high security. Cheap hardware becomes worn at hinged joints, becomes loose, and leaves the opener loose in the frame. Thus, the frame loses airtightness and performance. Look for Winkhaus, Segenia and Hoppe hardware: all quality German hardware brands.
7. Paints, varnishes and oils
Modern paint technology is also critical to the longevity of windows and doors. Automotive paint technology is now widely used on windows to provide durable paint finishes. Look for this feature, along with micro-porous paints which allow the timber to breathe, keep it stable and in good condition.
8. Aluminium cladding
Look for extruded rather than pressed aluminium with a minimum of 1.5mm thick, as this will resist knocks and dents of both building and everyday use. Check the system used to hold the aluminium cladding is fitted to allow both the aluminium and the timber to expand. During the heat of the summer, dark anthracite windows in particular can get hot and the aluminium will expand and move. Quality systems, like the Gutmann system for example, are designed to allow this movement and the cladding will not become loose. Welded corner seams ensure that the corners of the aluminium do not become misaligned with age.
Finally, when it’s cold outside and warm inside, the window will lose heat. Efficient German composite windows have a low U-value, which is a measure of how much heat they lose. You will see Uw value, which measures the entire window, and Uf and Ug which in isolation are largely irrelevant.
Check the Uw values of the window, as this tells you the thermal performance of the entire unit. Attention seeking marketing materials often quote the Uf (frame) Ug (glass) to display a lower figure.
If you want to get technical, check performance statistics such as wind Loading resistance, air permeability, air and water tightness. Compare these, as you will be very surprised how poorly many windows perform in these areas and are performance statistics that are regularly ignored, but are critical to a window’s real performance.
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