# How window choice affects your building energy certificate Windows are one of the most significant factors in a building’s energy efficiency — here is what to consider so your project reaches its target certificate class. Every new building and many renovations in Latvia require an energy certificate that defines the building’s energy-efficiency class. Window choice is one of the factors that can significantly influence this class — either positively or negatively. What exactly should you know when planning a project? ## Why are windows such an important factor? Windows are one of the places in a building where heat escapes most easily — compared with walls or roofs, the thermal transmittance of windows is usually significantly higher. This means that window choice can either help achieve a higher energy-efficiency class or become a "weak point" in an otherwise well-insulated building. ## What determines a window’s impact on the certificate? ### U-value (thermal transmittance coefficient) A lower U-value means better thermal insulation. This indicator is used directly in energy-efficiency calculations during the building certification process. ### Glazing type Double or triple glazing, as well as special coatings such as low-emissivity or "low-E" glass, directly affect the U-value and therefore the overall calculation. ### Frame material and construction Both PVC and aluminium profiles can achieve high energy-efficiency ratings, but the specific profile construction (number of chambers, material thickness) affects the final result. ### Installation quality Even a window with an excellent U-value will not deliver the expected effect if installation is inaccurate — heat loss through poorly sealed joints can significantly affect real, not just theoretical, energy efficiency. ## What does this mean at the project planning stage? For architects and developers working on projects with defined energy-efficiency requirements — for example, to qualify for certain support programmes or certification classes — window specifications should be evaluated at an early design stage, not as a last-minute choice. ## Practical tips - Request specific U-value data already at the quotation stage - Align the window specification with the project’s overall energy-efficiency targets - Ensure installation quality is documented if the certification process requires it ## Common mistake Choosing windows based on price alone, without assessing their impact on the building’s overall energy certificate, can lead to the building failing to reach the planned energy-efficiency class — which in turn can affect both project costs and compliance with regulatory requirements. ## Related reading Cheap vs quality windows → What is a multi-layer sealing contour? → How many glazing chambers do you need? → ## Working on a project with specific energy-efficiency requirements? Get in touch to discuss how the right window specification can help you reach your project goals. Contact us