Comparing Windows and Glass: Acoustic Isolation and Energy Efficiency Guide

The Importance of Choosing the Right Windows for Acoustic and Energy Efficiency

Acoustic Isolation

Noise pollution can significantly affect the comfort and functionality of a building, whether it’s a home, office, or public space. Windows are one of the weakest points in a building’s structure for soundproofing. Poor-quality windows can allow a lot of external noise—like traffic, construction, or neighboring activities—into your space, disrupting peace and productivity.

Acoustic windows are designed to reduce the transmission of sound from outside, creating a quieter indoor environment. The effectiveness of a window in blocking sound is measured by its Sound Transmission Class (STC) rating. The higher the STC rating, the better the window is at reducing noise.

Energy Efficiency

Windows are also key contributors to a building’s overall energy efficiency. Poorly insulated windows can allow heat to escape in winter and let excess heat in during summer, leading to higher energy costs for heating and cooling. Energy-efficient windows are designed to improve the building’s thermal performance, keeping indoor temperatures stable and reducing energy consumption.

The energy efficiency of windows is measured by their U-value (thermal transmittance), with a lower U-value indicating better insulation. Windows with low-emissivity (Low-E) coatings and double or triple glazing are often recommended for improving a building’s energy performance.

But be careful! The window specifications is not everything. The way of installation, where is it specifically placed and how it is also very important, as you can create other problems or make the windows not isolating enough, for example.

Comparing Different Types of Windows and Glass

Let’s look at how various types of windows and glass compare when evaluated on acoustic isolation and energy efficiency:

1. Single-Glazed Windows

Single-glazed windows consist of one layer of glass, making them the most basic and least expensive option. However, when it comes to both acoustic isolation and energy efficiency, they perform the poorest.

• Acoustic Isolation (STC Rating): Around 27 to 30.
  • Single-glazed windows offer very limited soundproofing. The single layer of glass allows sound waves to pass through easily, making them unsuitable for noisy environments.
• Energy Efficiency (U-value): Around 5.0 to 6.0 W/m²K.
  • These windows also allow a significant amount of heat to escape or enter, leading to higher energy consumption for heating and cooling. Single glazing offers minimal insulation against temperature changes, making them inefficient in terms of energy savings.

Recommendation:

• Single-glazed windows are rarely recommended in modern architecture unless cost is the primary concern, and the building is in a quiet, mild climate where energy loss and noise aren’t major issues.
• Nowadays it is almost never an option, even if you specifically want to install them.

2. Double-Glazed Windows

Double-glazed windows consist of two layers of glass with a gap (usually filled with air or gas) between them. This setup provides much better thermal insulation and acoustic performance than single-glazed windows.

• Acoustic Isolation (STC Rating): Around 33 to 38.
  • The air or gas-filled gap between the glass panes helps reduce the transmission of sound. However, the exact level of soundproofing depends on the thickness of the glass and the size of the gap, apart from installation, of course. For better acoustic isolation, varying the thickness of the two panes (e.g., 4 mm and 6 mm glass) can be more effective than using two panes of the same thickness.
• Energy Efficiency (U-value): Around 1.2 to 2.0 W/m²K.
  • Double glazing significantly reduces heat transfer, keeping indoor temperatures more stable. The gap between the panes acts as a barrier to heat flow, making these windows much more energy-efficient than single-glazed ones.

Recommendation:

• Double-glazed windows are an excellent choice for most residential and commercial buildings. They provide a balance of sound reduction and energy savings, making them suitable for urban environments or areas where thermal efficiency is a priority.
• While trying to be cost effective, it is always a good option to increase the gap between the panes rather than making other decision. It Is cheap and effective taking into account the cost.

3. Triple-Glazed Windows

Triple-glazed windows consist of three panes of glass with two air or gas-filled gaps between them. They offer superior thermal insulation and acoustic isolation compared to both single- and double-glazed windows. These are the usual windows used for PasivvHouse buildings, a highly energy efficiency kind of buildings.

• Acoustic Isolation (STC Rating): Around 40 to 44.
  • The additional layer of glass and extra air or gas gap further reduce sound transmission, making triple glazing ideal for buildings located in noisy environments, such as near airports or busy roads. The multiple panes absorb and deflect more sound waves than double-glazed windows.
• Energy Efficiency (U-value): Around 0.8 to 1.2 W/m²K.
  • Triple-glazed windows are highly energy-efficient, providing excellent insulation against heat loss in winter and keeping interiors cool in summer. These windows are particularly recommended for colder climates or buildings designed to meet high energy efficiency standards, such as Passive House certification.

Recommendation:

• Triple-glazed windows are the go-to choice for those prioritizing maximum energy efficiency and acoustic comfort, especially in extremely noisy or cold environments. However, they come at a higher cost, so they may not be necessary for all projects.
• As the costs go up, the way of installating them gets more important. It is highly advisable to install these kind of windows very well, so the extra expenses are not wasted due to thermal or acoustic bridges.

4. Acoustic Laminated Glass

Acoustic laminated glass is a special type of glass designed specifically for soundproofing. It consists of two or more layers of glass with a polyvinyl butyral (PVB) interlayer, which helps absorb sound vibrations.

• Acoustic Isolation (STC Rating): Around 40 to 45.
  • Laminated glass offers superior soundproofing, especially against high-frequency noise. The PVB interlayer dampens sound vibrations, making this glass ideal for applications where acoustic performance is a top priority, such as recording studios or high-traffic urban areas.
• Energy Efficiency (U-value): Similar to double-glazed windows, around 1.2 to 2.0 W/m²K when combined with a double-glazing unit.
  • While acoustic laminated glass is primarily designed for soundproofing, it also contributes to energy efficiency when used in double- or triple-glazed setups. The multiple layers provide good thermal insulation.

Recommendation:

• If noise reduction is your primary concern, acoustic laminated glass is an excellent choice. It works particularly well in double- or triple-glazed windows, where you can combine both acoustic and energy efficiency benefits.
• It is the best option against noise, but it is a good idea to prove cheaper solutions and trying to assess the problem as a whole.

5. Low-E Glass

Low-emissivity (Low-E) glass is coated with a thin metallic layer that reflects infrared energy (heat) while allowing visible light to pass through. This helps improve the energy efficiency of windows.

• Acoustic Isolation (STC Rating): Depends on whether the Low-E glass is single-, double-, or triple-glazed, but generally around 33 to 44.

• • The Low-E coating itself does not affect soundproofing, but when combined with double or triple glazing, the overall window will provide good acoustic isolation.

• Energy Efficiency (U-value): Around 1.0 to 1.5 W/m²K when used in double glazing.

• • Low-E glass is highly energy-efficient, reducing heat transfer and lowering heating and cooling costs. It’s particularly effective in buildings exposed to extreme temperatures, as it helps keep interiors warm in winter and cool in summer.

Recommendation:

• Low-E glass is an excellent option for projects focused on energy savings without compromising on natural light. When combined with double or triple glazing, it provides a well-rounded solution for both energy efficiency and acoustic performance.

Other Factors to Consider

Frame Material

The type of window frame also plays a role in both acoustic isolation and energy efficiency:

• Wood frames provide good insulation and contribute to energy efficiency, but they may require more maintenance.
• Vinyl or PVC frames are affordable, energy-efficient, and low-maintenance, making them a popular choice.
• Aluminum frames are durable and strong but tend to conduct heat, reducing energy efficiency unless they are thermally broken (fitted with an insulating barrier).

Materials are anyway always general considerations. It always depends on the specifications of the manufacturer. There are many aluminium frames with better performance than wood, for instance.

Gas Fillings

In double or triple glazing, the gap between the panes can be filled with either air or an insulating gas such as argon or krypton. Gas fillings provide better insulation than air alone, improving both the thermal and acoustic performance of the window.

• Argon gas is the most commonly used and provides a good balance of performance and cost.
• Krypton gas offers better insulation but is more expensive, often used in high-performance windows like triple glazing.

They are a good option but they are not going to make a huge difference themselves.

Conclusion: Finding the Right Balance Between Acoustic Isolation and Energy Efficiency

Choosing the right windows for your building involves balancing acoustic needs and energy efficiency. At Leukos Arquitectura, we recommend assessing the specific requirements of your project, whether it’s blocking out noise or focusing on energy efficiency.

We always recommend the assessment of a professional as there are many things to consider while choosing new windows and glass. And sometimes choosing between them can be a real headache.

Let me know your thoughts in the comments!