Energy-Saving Windows: how to improve your home’s efficiency

How to assess your house’s energy efficiency

Energy efficiency depends on various factors that determine a building’s energy consumption and environmental impact. The main elements to analyze include:

• the condition and type of heating and cooling systems;
• thermal insulation of the roof, walls (exterior wall cladding), floors and windows;
• the presence of systems for generating renewable energy (e.g. photovoltaic systems).

Based on the data collected, the building is rated on a scale from A4 (very efficient) to G (inefficient) in a document known as the Energy Performance Certificate (EPC).

Even windows and doors are certified for energy efficiency, through a label that assigns them a grade from A to G. This classification, regulated by specific standards, helps select the solutions most suitable for the climate in your area.

How much do windows and doors impact savings?

A great deal: drafty windows and thermal bridges are among the primary causes of high energy consumption and costly bills. Windows and doors alone can account for up to 40% of a home’s thermal energy loss! Now it’s surely clear how windows and doors are one of the most important factors to consider when discussing energy efficiency.

Outdated, poor-quality, or improperly installed windows and doors promote the formation of thermal bridges, nullifying all of the energy-saving efforts, causing significant heat loss in winter and increasing overheating in summer.

When aiming to improve your home’s energy efficiency, it’s important to consider replacing existing windows with new, high-performance models. These advanced solutions provide excellent insulation, ensuring energy savings in every season.

Installing new high-energy efficient windows guarantees these benefits:

• the elimination of drafts, thermal bridges and improved insulation;
• reduced energy consumption, and thus lower heating costs;
• a higher energy classification on the building’s Energy Performance Certificate.

Tax deductions for energy-saving windows in Italy

In Italy, in 2025, those who decide to replace old windows with more efficient models can benefit from two main tax incentives: the Renovation Bonus and the Ecobonus. Both incentives allow homeowners to recover part of the expenses incurred for the purchase and installation of new windows, but they differ in terms of scope and spending limits.

If interested, you can read more about it here (in Italian): Detrazioni Fiscali 2025.

How to choose high energy efficient windows?

Energy-saving doors and windows are designed to provide excellent thermal and acoustic insulation, reducing heat loss and improving energy savings.

But what parameters define the efficiency of a window in practice? Simply put, there are a set of technical specifications regarding a door or window’s ability to insulate the indoor environment, reduce energy consumption and ensure living comfort.

Of course, the choice of door and window frames should be tailored to the specific needs of the project, so it’s advisable to rely on companies with a solid expertise.

1. Thermal transmittance (Uw)

It measures the heat flow that passes through the window under stable conditions, expressed in W/m²K (Watts per square meter Kelvin). This parameter depends primarily on the frame materials, the transmittance of the glass, and the spacer between the glass panes.

Lower values indicate better thermal insulation: for example, a Uw of 1.0 W/m²K is much more efficient than 2.5 W/m²K. For windows with good energy efficiency, a value of ≤ 1.4 W/m²K is recommended, while highly energy-efficient frames should have ≤ 1.0 W/m²K.

2. Solar factor (g)

It indicates the amount of solar energy that the window allows to enter inside, expressed as a percentage (%). High values (50-70%) are recommended for cold climates to gain solar heat, while low values (20-40%) are preferable in hot climates to reduce overheating.

3. Acoustic insulation (Rw)

It measures the window’s ability to reduce external noise, expressed in dB (decibels). Higher values indicate better acoustic insulation: for example, a window with Rw ≥ 40 dB is ideal for particularly noisy areas and ensures optimal soundproofing.

4. Air tightness

It classifies the window’s ability to prevent air infiltration under pressure, on a scale from 1 (low tightness) to 4 (maximum tightness). Doors and windows with a high air tightness are crucial to avoid heat loss and maintain a constant indoor temperature.

5. Water tightness

It indicates the window’s ability to resist water infiltration during heavy rain or strong winds. It is classified from 1A (minimum resistance) to 9A (maximum resistance).

6. Wind resistance

This measures the window’s ability to withstand wind pressure without deforming or losing its properties, classified from A1 (low resistance) to C5 (maximum resistance).

7. Glass types

The window glazing significantly affects its energy performance. Energy efficient window glass (Low-E) reduces heat loss and improves thermal insulation; additionally, installing double- or triple-glazed windows enhances both thermal and acoustic insulation, due to the presence of gaps filled with insulating gases (such as argon).

8. Frame materials

The construction materials influence both thermal insulation and the durability of doors and windows. uPVC frames provide excellent performance with minimal maintenance and cleaning; wooden frames offer natural insulation but require more care; finally, thermal break aluminium frames are ideal for both strength and longevity.

9. Thermal spacers (Warm-edge)

These are profiles placed between the panes of glass in double or triple glazing, to separate them and improve the overall thermal insulation of the window. Their presence reduces heat loss along the edge of the glass, minimizing thermal bridges.

10. Transparency and Light Transmittance (Lt)

It measures the amount of natural light that passes through the window, which is crucial for visual comfort inside the home. High values improve indoor brightness, reducing the need for artificial lighting and its associated energy consumption.

11. Quality certifications

Ad esempio la marcatura CE per gli infissi, che garantisce la piena conformità alle normative europee, e la certificazione PosaClima, riconosciuta a livello nazionale per la qualità dei materiali costruttivi e l’installazione con esperti specializzati.

For example, the CE marking for window and door frames ensures full compliance with European regulations, and the PosaClima certification, recognized nationally in Italy for the quality of construction materials and expert installation.

DQG: windows and doors for high energy performances

Choosing DQG means opting for the best: all our certifications are not only a guarantee of products’ quality but also of flawless installation, carried out with innovative materials that ensure optimal insulation and complete elimination of thermal loss or infiltrations.

With our Made in Italy doors and windows, you can rely on:

• Qualified installation: DQG technicians have earned the title of “PosaClima Expert Installer and Window Opening Renovation Technician” after completing specialized training courses, ensuring precise and certified installation.
• 10-year warranty: installation of doors and windows with the PosaClima Premium Plus system is backed by a 10-year warranty, ensuring the full functionality of the frames and long-lasting performances without compromise.

Find out more about our company and explore the DQG product range!