Window Thermal Parameters
Window Light and Energy Parameters
Window Acoustic Parameters
Window Weather Resistance Parameters
Summary
Window Parameters Explained | What Matters Most When Choosing the Right Windows?
Window parameters play a key role when choosing windows, so it is important to understand their meaning and impact. When purchasing windows, investors often encounter mysterious markings that are not always immediately clear or intuitive. However, it is important to remember that each symbol represents a specific property that affects the window’s performance. Understanding window parameters allows you to consciously select a product that will meet your building’s expectations and needs.
In this article, we will explain step-by-step what the most important window parameters mean and why they matter. We will also discuss which parameters most affect user comfort and long-term maintenance costs. If you are planning to replace or purchase new windows, you should read this information to make smart decisions. Every window parameter, even if it seems minor, actually impacts daily functioning and the comfort of building occupants. In the following parts of the article, we will thoroughly explain parameters like Uw, Uf, Ug, Lt, g and Rw. With this knowledge, it will be easier to evaluate offers from manufacturers and choose the solution best suited to your needs.
Window Thermal Parameters – Uw, Uf, Ug
Uw – overall heat transfer coefficient of the window
The Uw parameter is one of the most important window parameters, describing the heat transfer rate through the entire window unit. The lower the Uw value, the better the window’s thermal insulation, which significantly reduces heating costs. It is always important to check whether the manufacturer provides the Uw for the complete window and not just for the glazing.
Uf – frame heat transfer coefficient
The Uf parameter describes the amount of heat transferred through the window frame and sash without considering the glass. Modern window systems offer frames with multiple chambers and thermal breaks to significantly lower the Uf value. Since the frame affects overall window parameters, it is crucial to choose frames with good thermal performance.
Ug – glazing heat transfer coefficient
The Ug parameter relates only to the glazing unit and measures how much heat passes through the glass itself. Lower Ug values mean better thermal performance, which becomes critical when designing large glazed areas. To improve window parameters in energy-efficient homes, it is best to select glazing with Ug values below 1.0 W/m²K.
Window Light and Energy Parameters – Lt, g
Lt – light transmittance
The Lt parameter defines the percentage of natural light that passes through the window glazing into the building’s interior. Higher Lt values mean brighter interiors, helping reduce the need for artificial lighting during the day. Therefore, it is important to consider this window parameter, especially in homes, offices, and schools where visual comfort matters.
G – solar heat gain coefficient
The g parameter shows how much solar energy passes through the glazing into the building and impacts indoor temperatures. A higher g value increases solar heat gains, which can be beneficial in winter but problematic in summer. When designing energy-efficient homes, it is important to balance window parameters to optimize heat gain and prevent overheating.
Window Acoustic Parameters – Rw
Rw – acoustic insulation coefficient
The Rw parameter measures how effectively a window blocks external noise from entering the interior of a building. Higher Rw values provide better sound insulation, which greatly improves daily comfort, especially in noisy environments. Therefore, it is important to consider this window parameter when selecting windows for homes near busy roads or railways.
Typically, windows with a Rw around 32–36 dB work well in standard conditions, while windows with Rw above 40 dB are recommended for high-noise areas. Additionally, laminated acoustic glass or thicker glazing units can significantly improve the acoustic window parameters.
Window Weather Resistance Parameters
Wind load resistance
Wind load resistance measures how well a window withstands pressure from wind without permanent deformation or loss of function. Higher resistance classes, such as Class C, offer better protection against strong winds, which is important in exposed locations. Therefore, it is important to choose window parameters that match the specific environmental conditions of the building’s location.
Water tightness
Water tightness defines the pressure level at which water begins to leak through the window into the building interior. Higher water tightness classes mean better protection during heavy rain and strong winds, preventing damage to the building. In standard single-family homes, water tightness classes like 5A or 6A are often sufficient, but areas with heavy rainfall may require higher classes. Therefore, it is important to check this window parameter carefully when selecting windows for demanding environments.
Summary
Knowing window parameters helps you make informed decisions and select products that match your building’s specific needs. Thermal insulation, light transmission, acoustic performance, security, and weather resistance are key window parameters that directly affect comfort. Therefore, it is important to focus on the most critical parameters like Uw and Ug when comparing different window options.
Always check whether manufacturers provide full window parameter values, not just selected parts like glass performance. Well-chosen window parameters lead to lower building maintenance costs, better daily comfort, and increased safety. Therefore, before purchasing, it is worth carefully reviewing the technical specifications, verifying certifications, and consulting an expert to avoid costly mistakes.
Partner with a trusted industry expert
Searching for an opening joinery supplier
for your ongoing projects? Complete the form – we’ll provide a custom proposal.
Our sales representative will reach out to you within 48 hours
to discuss how a potential collaboration could look.
During the conversation, you’ll learn more about our terms of cooperation.