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.

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.