25.09.2026

Double Glazing U-Value: Fundamentals, Calculation, and Practical Application

Building design

A contractor in white overalls applying spray paint on a roof. Photo: omerhaktan / Unsplash

Anyone who evaluates a building’s energy efficiency or renovates it cannot ignore one key parameter: the heat transfer coefficient, or U-value for short. For windows, this value significantly determines how much heating energy is lost through the glazing, whether condensation forms on the pane, and whether the room temperature near the window is perceived as comfortable. The U-value for double-pane glazing is not some abstract laboratory concept, but a physically precise measure with direct implications for energy efficiency, comfort, and building physics.

What the U-value means in physical terms and how it differs from related parameters
How the heat transfer coefficient of double-pane glazing is calculated and what factors determine it
What typical U-values for double-pane glazing are realistic and how they compare to other types of glazing
What role gas filling, coatings, spacers, and the edge seal play
How the Ug-value of the glazing, the Uf-value of the frame, and the Psi-value of the edge seal interact to determine the Uw-value of the entire window
What regulatory requirements and energy standards apply to double-pane glazing
When double glazing is sufficient and when switching to triple glazing makes sense
What building physics risks arise when U-values are too high and how to identify them

What the U-value is: definition, unit, and physical basis

The U-value, officially known as the heat transfer coefficient, describes the steady-state heat flux that flows through one square meter of a building component per second when the temperature difference between the two adjacent air layers is exactly one kelvin. The unit is W/(m²K), or watts per square meter per Kelvin. A low U-value indicates good thermal insulation, while a high U-value indicates significant heat loss. For double-pane glazing, the U-value typically ranges between 1.0 and 1.4 W/(m²K), depending on the design, while single-pane glazing can reach values of 5.0 W/(m²K) or higher.

The physical basis lies in Fourier’s law of heat conduction and the mechanisms of heat transfer. Heat flows through a building component in three ways: by conduction in solids, by convection in gases and liquids, and by thermal radiation. In glazing, convection and radiation in the air space between the panes, as well as heat transfer at the surfaces, are the dominant factors. Heat conduction through the glass itself is comparatively low due to the thin pane thickness of just a few millimeters. The U-value of double-pane glazing is therefore primarily determined by the properties of the air space, the gas filling, and any coatings.

It is important to distinguish between the different U-value variants that coexist in window construction. The Ug value (g for “glass”) describes only the glazing itself, without considering edge effects. The Uf value (f for “frame”) applies to the frame. The Uw value (w for “window”) is the overall value of the window, including the glazing, frame, and perimeter seal. When you look up the U-value for double-pane glazing in product data sheets, you will usually find the Ug value listed there. However, in a building’s energy performance certification, the Uw value of the entire window is the decisive factor.

Structure of double glazing: layers, gas filling, and coating

Double-pane glazing, also known as double-pane insulated glazing or double glazing, consists of two glass panes held apart by a perimeter spacer and hermetically sealed at the edges. The resulting air space between the panes is the actual insulating medium. In modern designs, this space is filled not with air but with noble gases, primarily argon or krypton, which have lower thermal conductivity than air and thus reduce convective heat transfer within the space.

Argon is the most commonly used filling gas because it is cost-effective, chemically inert, and available in sufficient purity. Its thermal conductivity is approximately 0.017 W/(mK), compared to 0.026 W/(mK) for air. Krypton has an even lower thermal conductivity of about 0.009 W/(mK) and allows for narrower air gaps while providing the same insulating effect, but it is significantly more expensive. The optimal air gap for argon filling is about 14 to 16 millimeters; at larger gaps, convection sets in within the gas and reduces the insulation value again.

The second key component is the thermal insulation coating, known in technical jargon as a Low-E (Low Emissivity) coating. This ultra-thin layer of metal oxide, usually silver or tin oxide, is applied to the inner surface of one of the two panes, typically to the side of the outer pane facing the room (surface 2 in the counting convention from the outside to the inside). The coating reflects long-wave thermal radiation back into the room, thereby significantly reducing the radiative component of heat transfer. It is only the combination of a noble gas fill and a Low-E coating that enables the U-value of double glazing to fall below 1.1 W/(m²K), which is now considered the standard for new buildings.

Older double-pane glazing units without gas filling or a coating—such as those installed up through the 1990s—achieve Ug values ranging from 2.8 to 3.0 W/(m²K). These values no longer meet today’s energy efficiency requirements and are a common reason for replacement during renovations. The difference between old air-filled double glazing and modern coated argon-filled glazing is more than a factor of two, which has a significant impact on a building’s heating energy balance.

Calculation of the U-Value for Double Glazing: Standards, Methods, and Influencing Factors

The calculation of the Ug-value for glazing is governed by the European standard EN 673. This standard describes an iterative calculation method that accounts for heat transfer by conduction, convection, and radiation within the air space between the panes, as well as the heat transfer resistances at the outer surfaces. The boundary conditions specified are an indoor temperature of 20 degrees Celsius and an outdoor temperature of 0 degrees Celsius, as well as defined heat transfer resistances. The resulting U_g value is thus a standardized comparative value under laboratory conditions, not a measured value under real-world climatic conditions.

The standard EN ISO 10077 applies to the overall window value Uw. It describes how the Ug, Uf, and the linear heat transfer coefficient Psi of the perimeter seal (also referred to as the Psi value or perimeter seal coefficient) are combined to determine the Uw value. The edge seal is the connection zone between the glazing and the frame, where the spacer is located. Metallic spacers made of aluminum conduct heat well and create a pronounced thermal bridge at the edge of the glass, which worsens the window’s effective U-value compared to the Ug value alone. So-called “warm edge” spacers are made of thermally insulating materials such as stainless steel, plastic, or composite materials, which reduce this effect.

The formula for the Uw value, simplified, is: Uw is calculated as the area-weighted sum of Ug multiplied by Ag (glass area) and Uf multiplied by Af (frame area), plus the sum of the edge lengths multiplied by the respective Psi value, divided by the total window area. This calculation shows that a low Ug value alone is not sufficient if the frame has a high Uf value or if the edge seal is poorly executed. In a window with a large frame-to-glass ratio, a poor Uf value can raise the Uw value significantly above the Ug value.

In practice, this means that the U-value of double glazing is only one of several factors affecting the overall window performance. An Ug of 1.0 W/(m²K) combined with an aluminum frame with an Uf of 2.0 W/(m²K) and a conventional aluminum spacer can result in an Uw of 1.4 to 1.6 W/(m²K). The same glazing in a well-insulated wood frame with Warm-Edge spacers may achieve a Uw of 1.1 to 1.2 W/(m²K). A system-wide analysis is therefore essential.

Regulatory Requirements and Energy Classification

In Germany, the Building Energy Act (GEG) regulates the minimum energy performance requirements for windows in new construction and for major alterations to existing buildings. The GEG stipulates a maximum Uw value of 1.3 W/(m²K) for windows in new construction, whereby the entire building is evaluated using a reference building method and individual building components may deviate from this value as long as the building as a whole meets the requirements. For renovations of existing buildings, maximum values also apply when replacing windows, as specified in a table within the GEG.

DIN 4108-2, which regulates thermal insulation and energy conservation in buildings, contains requirements for minimum thermal insulation, which, among other things, ensures that interior wall surfaces do not drop below the dew point temperature of the indoor air. For windows, the temperature factor fRsi at the inner surface of the edge seal is relevant. An excessively high U-value for double-pane glazing, combined with a poorly constructed spacer system, can cause the glass surface or the frame area near the window to remain permanently below the dew point of the indoor air, which promotes condensation and, consequently, mold growth.

In the European context, the EN 14351-1 standard specifies the performance characteristics of windows, including heat transfer. The CE mark on window products certifies compliance with this standard. The Passive House standard, developed by the Passive House Institute in Darmstadt, imposes significantly stricter requirements: Here, triple-pane glazing with U_g values ranging from 0.5 to 0.7 W/(m²K) is typically used, as double-pane glazing cannot achieve the required U_w values of less than 0.8 W/(m²K).

Double-pane versus triple-pane glazing: When is double glazing sufficient?

The decision between double-pane and triple-pane glazing is not a matter of principle, but rather a balance between energy efficiency, cost, weight, and intended use. Modern double glazing with a Ug value of 1.0 to 1.1 W/(m²K) meets the GEG requirements for new construction in many cases, provided the frame and edge seal are properly constructed. For a well-insulated energy-efficient home meeting KfW Class 55 standards or better, double glazing is generally no longer sufficient, because the required Uw value of the entire window must be below 1.0 W/(m²K).

Triple glazing adds a third pane and a second air space, which reduces the Ug value to 0.5 to 0.7 W/(m²K). The trade-off is that the glazing is heavier, which places greater demands on hardware, frames, and masonry connections, as well as a slightly reduced light transmittance and a lower g-value (total energy transmittance). The g-value describes the proportion of incident solar radiation that enters the room as heat. For triple-pane glazing, it typically ranges from 0.50 to 0.55, and for double-pane glazing, from 0.60 to 0.65. In passive solar designs, where south-facing windows are intentionally used as a heat source, the higher g-value of double-pane glazing can be energetically advantageous.

For retrofits of existing buildings, double-pane glazing is often the more economically sensible choice when replacing single-pane glazing or old double-pane glazing without a coating. The jump from a U-value of 2.8 to 1.1 W/(m²K) is significant in terms of energy efficiency and easily justifies the investment in many cases. While the additional reduction from 1.1 to 0.6 W/(m²K) achieved with triple glazing yields further savings, it pays for itself only over long periods of use or when heating costs are very high.

Building physics risks associated with an inadequate U-value: condensation, mold, and comfort

A U-value that is too high for double-pane glazing has direct consequences for the interior wall surface and the indoor climate. The interior surface of a glazing unit with a U_g of 2.8 W/(m²K) reaches a surface temperature of about four to five degrees Celsius when the outside temperature is minus ten degrees and the inside temperature is twenty degrees. At a relative indoor humidity of fifty percent, the dew point of the indoor air is approximately nine degrees Celsius. The glass surface is thus well below the dew point, and condensation is the inevitable result. This condensation runs down the frame, saturates the connection area, and promotes mold growth in the soffit.

Under the same conditions, modern double-pane glazing with a U-value of 1.1 W/(m²K) achieves an interior wall surface temperature of approximately thirteen to fourteen degrees Celsius. At a normal indoor relative humidity of fifty percent, the dew point is around nine degrees, so the glass surface remains well above the dew point. Condensation does not occur under normal conditions of use. Only under conditions of very high indoor humidity—such as those that can occur intermittently in bathrooms or kitchens—or at extreme outdoor temperatures can condensation form briefly even on modern double-pane glazing.

In addition to the risk of condensation, the U-value of the glazing affects thermal comfort in the room. Cold glass surfaces create a sense of discomfort due to radiative asymmetry, which users perceive as a draft even though no actual draft is present. The human body emits thermal radiation toward the colder glass surface, which is perceived as a sensation of cold. This effect is significantly less pronounced in glazing with a U_g of 1.1 W/(m²K) than in glazing with a U_g of 2.8 W/(m²K) and contributes significantly to user satisfaction, regardless of the heating energy balance.

Quality Assurance, Product Labeling, and Installation

The declared Ug value of glazing is only meaningful if it is determined in accordance with applicable standards and substantiated by corresponding test certificates. Reputable manufacturers certify the Ug value in accordance with EN 673 and provide test reports from accredited testing institutes. When selecting glazing, attention should be paid to the specifications regarding gas filling, the filling percentage (typically over ninety percent argon), the type of coating, and the type of spacer, as these parameters determine the actual U-value.

The installation of the glazing in the frame and the installation of the window into the building envelope are just as critical as the product characteristics. A properly executed window connection with thermal bridge-free integration into the insulation layer of the exterior wall is a prerequisite for ensuring that the window’s nominal U-value is actually achieved under real-world conditions. Poorly executed connections with thermal bridges at the lintel, the soffit, or the sill can significantly increase the window’s effective heat loss beyond the calculated U-value. Professional installation in accordance with the regulations of the Quality Association for Windows and Facades (QGF) or comparable guidelines is therefore not an optional extra, but a basic requirement for proper function.

The U-value of double glazing in the overall context of building energy efficiency

The U-value of double glazing is a precise, standardized, and practically significant parameter; however, it must always be considered in the context of the window system as a whole and the building system as a whole. Optimizing the glazing in isolation, without considering the frame, the edge seal, and the installation conditions, leads to unrealistic expectations and suboptimal results. Similarly, it is not possible to make a sensible choice of windows without knowing the building’s intended use, the orientation of the facade, the heating system, and the building’s overall energy balance.

In practice, modern double-pane glazing with U_g values between 1.0 and 1.1 W/(m²K), filled with argon, Low-E coating, and warm-edge spacers, are a technically mature and economically sound choice for the vast majority of renovation projects and for many new construction projects in the mid-efficiency range. Compared to older glazing, they offer a dramatic improvement in energy performance, prevent condensation problems under normal operating conditions, and noticeably improve thermal comfort.

Anyone who understands the physical principles behind the U-value, knows the relationships between gas filling, coatings, and the air space between panes, and has a grasp of how these are regulated by GEG and EN standards can make informed decisions: when planning new construction, renovating existing buildings, and evaluating product offerings. The U-value of double-pane glazing is thus not a minor technical detail, but a key parameter at the heart of any serious energy-efficient building assessment.

13.01.2026

Cooling routes in navigation systems – who integrates the well-being factor?

Building design

a-gruner-train-riding-along-a-street-next-to-tall-buildings-Q_2foPI_vmU — Children's train in Brasov, Romania. Photo by Fermoar.ro

Anyone navigating through the city in summer asks Google Maps for the quickest route – not the most pleasant one. But how much quality of life falls by the wayside when navigation systems ignore heat islands and shaded areas? Cooling routes could change that. But who is really taking the well-being factor seriously – and how far have we come in the DACH region with integrating it into digital urban mobility?

Definition and importance of cooling routes in urban planning
Technical basics: data sources, sensors and algorithms
Practical examples from Germany, Austria and Switzerland
Challenges of integration into navigation systems
Well-being as a new benchmark for urban mobility
Potentials and risks of data-driven cooling routes
Strategies for cooperation between planners, tech providers and cities
Prospects for a climate-resilient, liveable city

Cooling routes: What’s behind the new trend?

Anyone who walks in Berlin, Vienna or Zurich at the height of summer will be familiar with the problem: asphalt surfaces shimmer with heat, concrete walls store heat and getting from A to B feels like an involuntary sauna session. Traditional navigation, whether with a smartphone or in a car, has so far only known two parameters: fast and direct. But the consequences of urban heat islands have long been more than just a comfort problem. They affect health, quality of life and ultimately also social justice in urban areas. This is precisely where so-called cooling routes come in: Route recommendations that are not only optimized for speed, but explicitly for the thermal well-being of users.

The principle sounds simple, but is highly ambitious in terms of technology and planning. Instead of just reacting to traffic jam or road works reports, cooling routes take a variety of other factors into account: shadows cast by trees and buildings, current and forecast temperature data, humidity values, green areas, water surfaces, wind currents and even surface temperatures. The aim is to find the most pleasant – i.e. coolest and at the same time safest – route through the urban undergrowth. This is not about detours for the sake of it, but about real quality of life, which can be existentially important for many population groups, such as senior citizens or families with children.

The idea is not new, but only the latest advances in sensor technology, urban data processing and artificial intelligence are making it practicable. Cities such as Vienna and Paris are already experimenting with the first prototypes, while in German municipalities the topic is often still stuck on the drawing board – or is torn between responsibilities and data protection concerns. Current hot spells and growing urbanization show that the need for smart, climate-friendly mobility services is increasing rapidly.

Cooling routes are far more than just a digital gimmick for technology fans. They are an expression of a paradigm shift in dealing with urban climate: away from pure infrastructure planning and towards the proactive design of urban quality of life. Anyone who believes that route guidance is a purely logistical task is overlooking the potential that lies in linking climate data, urban design and digital navigation.

But as convincing as the concept sounds, the integration of cooling routes into existing navigation systems is anything but trivial. It requires a new planning culture, cooperation between the city, tech companies and science – and not least a clear attitude: is well-being in the city really more than just a marketing promise?

The technical basis: data, sensors and algorithms for cooling routes

Establishing cooling routes as an integral part of urban navigation requires a whole new wealth of data – and the ability to make it usable in real time. While conventional navigation systems are based on fixed map data and traffic reports, cooling routes need to access a wide range of environmental and climate data. This initially includes meteorological data such as temperature, humidity, UV radiation and wind speed. These are often recorded by urban weather stations, but increasingly also by sensor networks in the street. LoRaWAN sensors, such as those used in Hamburg or Zurich, provide precise measurements right down to the sidewalk – a real quantum leap compared to the coarse-grained data of the past.

But sensor data alone is not enough. The integration of geographic information systems (GIS), which provide detailed information on road width, surface materials, greenery, water areas and building heights, is crucial. This is the only way to precisely model the shadows cast by trees and façades, the course of fresh air corridors or the reflection of sunlight. Cities such as Vienna and Munich have already set up their own data platforms that can serve as a basis for developing cooling routes.

However, the real magic happens in the algorithm: modern route planners that are optimized for well-being have to weigh up a large number of competing factors. Should a route be slightly longer but significantly cooler? Is the shade on a particular route reliable or only available at certain times of day? How does the surface temperature affect subjective perception? This is where machine learning and simulation techniques are used to derive patterns from historical and current data and create forecasts. The challenge: the algorithm must not only deliver technical precision, but also map the complex interplay of climate comfort, safety and accessibility.

One factor that is often underestimated is the availability and quality of the data. While there is usually good climate data for main roads, many side streets, parks or backyards are still blank spots on the digital weather map. The integration of crowdsourcing approaches – for example by using sensor data from smartphones or wearables – can help here, but raises new questions about data protection and data sovereignty. Who is allowed to use which data and how? And how can sensitive location or health data be prevented from becoming a commodity?

Making cooling routes suitable for mass use therefore requires not only technical excellence, but also robust governance structures and close integration of urban planning, software development and data protection law. Only then can cooling routes develop their full potential – and actually integrate well-being into digital urban mobility.

Practical check: Who is integrating cooling routes – and what do the first applications look like?

A look at the practice shows: The integration of cooling routes into navigation systems is still in its infancy in the DACH region – but there are some promising initial approaches. Vienna is considered a pioneer: with the “Cool Vienna” project, the city presented a digital route planner back in 2021 that recommends the coolest routes through the city for pedestrians. It is based on high-resolution climate data, which is linked to information on shade zones, drinking fountains and green spaces. The application is directly integrated into the city service and is being continuously developed. Zurich is also working on similar concepts: in addition to temperature data, wind tunnel analyses and real-time measurements from the Smart City network are also incorporated into the navigation system.

In Germany, development has so far been more fragmented. While individual cities – such as Munich, Stuttgart and Frankfurt – have set up pilot projects for heat-resilient urban districts, there is usually still a lack of consistent integration into existing mobility apps. The Fraunhofer Institute is working with several local authorities to develop an open data standard for urban climate routes, but there is still a long way to go before it is widely used. One reason for this is that major navigation providers such as Google and Apple have so far been reluctant to integrate local climate data into their algorithms. This shows how important open interfaces and close cooperation between city authorities, research and the tech industry are.

Interest is also growing in Switzerland: Zurich, Basel and Bern are currently testing the linking of pedestrian routes with real-time climate data, in some cases even in combination with augmented reality features that allow users to visualize the progression of shadows on their smartphones. The aim is not only to plan heat resilience, but to make it tangible in everyday life. Initial user feedback shows that acceptance increases when the applications work intuitively and reliably – and when they offer real added value compared to traditional navigation.

An exciting side effect: the development of cooling routes also promotes cooperation between traffic planning, environmental agencies and urban development. Only when information on tree populations, surface temperatures, air pollutants and footpath networks is pooled can a complete picture be created for planning purposes. This not only creates better routes, but also provides impetus for improving the urban infrastructure – for example through targeted replanting, drinking water points or temporary shade providers.

Despite all the progress, the big challenge remains: how can cooling routes be turned from a niche into a standard? This requires clear political guidelines, integration into existing smart city strategies – and not least the courage to push through new forms of urban mobility, even against the established routines of traffic planning.

Well-being as a new benchmark: opportunities, risks and prospects

The integration of cooling routes into navigation systems is more than just an update for technology fans – it marks a paradigm shift in urban planning. Instead of speed and efficiency, the focus is shifting to people’s subjective well-being. This has far-reaching implications, not only for technical development, but also for the self-image of urban development. Well-being is a complex construct: it encompasses temperature comfort, quality of stay, accessibility, safety and even social aspects such as communication and participation. Anyone planning cooling routes must take all these dimensions into account and map them transparently.

But with the new focus on well-being, the requirements are also growing. The algorithms must be fair, comprehensible and adaptive. It must not happen that certain neighborhoods are systematically disadvantaged because, for example, their climate data is less well collected or their streets are less green. There is a risk of an algorithmic bias that cements or even exacerbates existing inequalities in urban space. To counteract this, we need open, verifiable systems and the consistent involvement of all relevant stakeholders – from the administration to the scientific community to the citizens themselves.

Another critical point is the commercialization of urban climate data. If navigation providers offer exclusive data access or premium functions for cooling routes, there is a risk of two-tier mobility: those who pay will walk in the shade, those who don’t will stay in the sun. That would be the opposite of what climate-resilient urban development aims to achieve. Cities and municipalities are called upon to create open data standards and to see the integration of feel-good routes as a common good – not as a luxury product.

However, the potential is enormous: cooling routes can not only make everyday life easier in hot summers, but also contribute to preventive healthcare, promote walking and cycling and strengthen social participation. They make climate change visible in everyday life and show concrete adaptation strategies. For planning, they open up new possibilities for scenario development, for example by showing how targeted greening measures or water features can improve the urban climate and mobility.

In the long term, cooling routes could become standard in every navigation application – provided that cities and providers understand well-being as a central leitmotif of urban mobility. Then navigation will no longer just be a question of efficiency, but a question of quality of life – and thus a genuine, climate-conscious innovation in urban space.

From vision to implementation: what planners, cities and tech providers need to do now

The path from the idea to the widespread implementation of cooling routes is rocky, but feasible – if the relevant players pull together. For planners, this means that urban development must no longer be seen solely as a question of land use and traffic management, but as a holistic design of the urban microclimate. New alliances are needed between urban climatology, mobility management, digitalization and participation. Landscape architects and urban designers in particular can contribute their expertise here by specifically integrating shade structures, green axes and fresh air corridors into public spaces – and actively providing the data for this.

Cities and municipalities are called upon to create open data platforms and interfaces. Innovative navigation apps can only be created if climate data, traffic information and geodata are freely accessible and machine-readable. It is worth taking a look at Scandinavia or the Netherlands, where open urban platforms have long been standard. At the same time, data protection and data sovereignty must remain a top priority in order to secure the public’s trust and prevent uncontrolled commercialization.

Tech providers, in turn, must have the courage to open up their algorithms to new feel-good parameters – and embrace the complexity of urban reality. This means moving away from rigid standard routes and towards flexible, learning systems that take equal account of climate, safety and quality of stay. It requires interdisciplinary teams that bring together urban climatology, software development and UX design – and the willingness to set new standards together with the cities.

One key to success lies in the active involvement of users. Only if the applications are intuitive, transparent and comprehensible will they be widely accepted. Feedback loops, participative workshops and open pilot projects are just as important here as traditional public relations work. Cooling routes must not remain a niche product for technology enthusiasts, but must be established as a natural part of urban mobility.

The result is a city that is not only built, but lived – and in which the well-being of all people is the focus. The integration of cooling routes into navigation systems is an important building block for the climate-resilient, liveable city of tomorrow. Those who act now are setting standards – and showing that urban planning can do more than just asphalt and traffic lights.

Conclusion: Cooling routes are more than just a feature – they are a quantum leap for urban well-being

Cooling routes in navigation systems mark the dawn of a new era of urban mobility – one in which people’s well-being is finally given the importance it deserves. They combine technological innovation, climate adaptation and social participation in a holistic approach that goes far beyond traditional transportation planning. The challenges are manifold: from data collection and the development of fair algorithms to open, participatory governance. But the opportunities are at least as great. Cooling routes not only make the city more pleasant, but also fairer, healthier and more sustainable.

To realize their full potential, they need the courage to cooperate, a willingness to rethink and a clear political agenda. Cities, planners and tech providers must work together to set new standards – for navigation that no longer just leads from A to B, but aims to improve quality of life. Because in the end, it’s not how quickly we get through the city that counts, but how we feel while doing so. And the cool route clearly has what it takes to become the new gold standard.

08.01.2025

Product

Under the sign of the circle

Building design

Aarhus Arkitektern developed the T60 shower head for Vola.

The design of the new “T60” hand shower by Aarhus Arkitekterne for Vola is based on clear geometries: The shower head consists of a round disk held by a cylindrical rod that serves as a handle. Rubber rings on the rod ensure a good grip and their arrangement corresponds to the eight jet-shaped rows of nozzles of the shower head.