In commercial buildings, window condensation isn’t just an annoyance—it can be a significant problem that affects the building’s performance, safety, and appearance. Whether it’s a foggy view that obscures natural light or moisture build-up that invites mold, condensation on commercial windows can signal deeper issues. Understanding why condensation happens and how advanced window technologies combat it is essential for building owners, facility managers, and contractors alike.

In this guide from Aeroseal, we’ll explore the causes of window condensation, its impacts on commercial spaces, and how modern condensation-resistant window systems work. We’ll also look at the testing standards that ensure window performance and provide tips for choosing the right window solutions for your building.

What Causes Window Condensation?

The Basic Physics of Condensation

At its core, condensation is a result of temperature differentials and humidity. When warm, moist air inside a building meets the cooler surface of a window, the moisture in the air condenses into water droplets. This is particularly common in colder climates or seasons when indoor heating raises the interior temperature, while the external glass remains cold.

This natural process is governed by the dew point—the temperature at which air becomes saturated, and water vapor turns into liquid. If the surface temperature of the window falls below the dew point, condensation forms.

Common Sources of Indoor Humidity in Commercial Buildings

Commercial buildings often have higher indoor humidity due to various activities and systems. Some of the most common sources include:

• HVAC systems that are improperly balanced
• Exercise and Aquatic Areas
• Commercial kitchens and restrooms
• Indoor plants and water features
• Building leaks and poor ventilation

Managing indoor humidity is a critical first step in preventing condensation, but it’s only part of the solution.

The Impact of Poor Insulation and Thermal Bridging

Insufficient insulation and thermal bridging—where heat flows through materials with poor thermal performance—can exacerbate condensation problems. Metal window frames, for example, readily conduct heat, causing the interior frame surface to drop in temperature and encourage moisture build-up. Without proper design and materials, windows become weak points in a building’s thermal envelope.

How Condensation Affects Commercial Buildings

Visual Impairment and Occupant Discomfort

Condensation obscures visibility through windows, blocking natural light and making spaces feel darker and less inviting. For commercial spaces like offices, schools, and retail environments, this can reduce occupant comfort and even productivity.

Mold and Mildew Growth

Persistent condensation creates damp surfaces that promote the growth of mold and mildew, which can compromise indoor air quality and pose health risks to building occupants. In fact, according to NIH, approximately 47% of residential buildings in the United States have visible mold or mold odor, often resulting from moisture issues such as condensation. ​

Damage to Window Frames, Seals, and Surrounding Materials

Water from condensation doesn’t stay put. It can seep into window seals, frames, and surrounding walls, causing warping, rot, and deterioration. Over time, this can lead to costly repairs and potential structural damage.

Increased Energy Costs

When windows fail to maintain a consistent temperature across their surfaces, HVAC systems must work harder to compensate. This drives up energy consumption and operating costs—especially in large commercial facilities.

The Science of Condensation Resistance

The Role of Window Glazing Technology

Double-pane or triple-pane glazing is one of the most effective defenses against condensation. By sandwiching insulating air or gas between multiple panes of glass, these windows maintain a warmer interior surface temperature and reduce the likelihood of condensation forming.

Low-E (Low Emissivity) Coatings

Low-E coatings reflect heat back into the building while letting in visible light. These microscopically thin layers of metal or metallic oxide improve thermal performance, keeping the inner glass surface warmer and minimizing condensation risk.

Gas Fills for Thermal Insulation

Inert gases like argon or krypton are often used to fill the spaces between glass panes. These gases are denser than air, providing better insulation and reducing the chance of the interior surface temperature falling below the dew point.

Warm-Edge Spacers to Reduce Thermal Bridging

Traditional metal spacers can conduct heat across the window assembly, encouraging condensation at the edges. Warm-edge spacers, made from less conductive materials, help maintain consistent temperature across the window and limit condensation build-up.

Frame Materials and Thermal Breaks

Window frames play a crucial role in condensation resistance. Frames with thermal breaks—insulating barriers within the frame material—reduce heat transfer and prevent cold spots where condensation can form.

Testing and Standards for Condensation Resistance

Understanding the CRF (Condensation Resistance Factor)

​The Condensation Resistance Factor (CRF) is a standardized metric developed by the American Architectural Manufacturers Association (AAMA) to evaluate a window’s ability to resist condensation. It provides a comparative rating of similar products under specified test conditions, allowing for the determination of conditions beyond which condensation may occur. Higher CRF values indicate better condensation resistance. ​

The CRF is determined through physical testing as outlined in AAMA 1503, “Voluntary Test Method for Thermal Transmittance and Condensation Resistance of Windows, Doors and Glazed Wall Sections.” This test involves placing the window in a controlled environment where temperatures and wind speeds are maintained at specific levels until steady-state conditions are achieved. The heat flow through the product and the surface temperatures of the frame and glass are measured to determine the CRF.

ENERGY STAR and NFRC Ratings

ENERGY STAR and the National Fenestration Rating Council (NFRC) provide standardized window ratings for energy efficiency, including condensation resistance. Products certified by these organizations meet stringent performance criteria and offer peace of mind to building owners.

ASTM Testing Methods

The American Society for Testing and Materials (ASTM) provides testing protocols for condensation resistance. ASTM E577 and ASTM E1105, for example, evaluate condensation formation under controlled temperature and humidity conditions.

Choosing the Right Window System for Your Building

Key Factors to Consider

Selecting the right condensation-resistant windows involves several considerations:

• Climate: Colder regions demand higher insulation and condensation resistance.
• Building Usage: Spaces with high humidity (like gyms or kitchens) require specialized solutions.
• Orientation: North-facing windows may experience less solar heat gain, making them more prone to condensation.

Balancing Performance with Cost

Investing in premium window features such as triple glazing and inert gas fills can significantly enhance a building’s energy efficiency and comfort. Triple-pane windows, for instance, have been shown to reduce heating energy consumption by an average of 12% and cooling energy use by 28% in a 1,500-square-foot home during specific evaluation periods. While the initial installation cost of triple-glazed windows is higher—averaging around $600 per window —​the long-term energy savings can offset this expense. Striking the right balance between upfront investment and anticipated energy cost reductions is crucial for maximizing return on investment.

Importance of Professional Installation and Airtight Sealing

Even the best windows won’t perform properly without correct installation. Airtight sealing and professional installation ensure that windows integrate seamlessly into the building envelope, minimizing drafts, leaks, and potential condensation points.

Conclusion

Condensation on commercial windows is more than an eyesore—it’s a warning sign of thermal inefficiency, indoor air quality risks, and potential building damage. By understanding the science behind condensation and investing in high-performance, condensation-resistant windows, building owners can protect their properties, improve occupant comfort, and lower energy costs.

At Aeroseal, we specialize in providing customized commercial window solutions that combine superior condensation resistance with energy efficiency and aesthetic appeal. Whether you’re retrofitting an existing building or designing a new facility, our team can help you select and install the right windows for your needs.

Contact Aeroseal

Ready to upgrade your building with condensation-resistant commercial windows? Contact Aeroseal today for a consultation or a customized quote. Explore our commercial window and door solutions and learn how we can enhance your building’s performance and comfort.