Electrically Heated Glass: A Smart Solution for Year-Round Thermal Comfort, Energy Efficiency, and Mold Control

Michael Mullock
May 25
3 min read

Updated: 2 days ago

In an era of smarter, more sustainable buildings, thermally active glazing—specifically UL-approved electrically heated glass—is emerging as a high-performance solution that addresses three critical building concerns: thermal comfort, energy efficiency, and moisture control.

When integrated with heat pumps and smart building management systems (BMS), electrically heated glass plays a transformative role in highly glazed environments where conventional HVAC strategies fall short. The result is a system that not only optimizes comfort and performance year-round but also meets or exceeds the thermal envelope performance defined by ASHRAE standards.

Why Moisture Matters: The Physics Behind Condensation and Mold

Warm air holds more moisture than cold air. For every 20°F (11°C) increase in temperature, air can hold nearly double the amount of moisture. When interior glass surfaces drop below the dew point, that moisture condenses into water droplets—setting the stage for mold growth, especially in thermally inefficient window and door systems.

Electrically heated glass prevents condensation by maintaining surface temperatures above dew point, directly addressing one of the root causes of indoor mold. By doing so, it supports compliance with ASHRAE 62.1 (Ventilation for Acceptable Indoor Air Quality) and ASHRAE 55 (Thermal Environmental Conditions for Human Occupancy), which emphasize humidity control, surface temperature stability, and thermal comfort.

Winter: Superior Comfort at Lower Energy Cost

In cold weather, electrically heated glass radiates gentle, even warmth into the space. This radiant heat allows the indoor air temperature to be set lower while still maintaining occupant comfort—reducing overall heating demand.

The result:

Enhanced thermal comfort near large glazed openings
Reduction in cold drafts and thermal stratification
Significant reduction in energy usage—especially when paired with low-temperature air-source heat pumps

This contributes toward envelope performance goals in ASHRAE 90.1, particularly for buildings with large fenestration ratios.

Summer: Passive Heat Gain Reduction

In summer, the heating function of the glass is disabled or modulated, and its Low-E coating passively reflects solar infrared radiation, reducing unwanted heat gain without sacrificing daylight or views. This minimizes reliance on air conditioning and supports peak load reduction—a critical metric in ASHRAE 90.1.

Additionally, the thermal buffering offered by radiant glass improves thermal comfort near the glazing, which is a known weak spot in cooling-dominant climates.

Integration with Heat Pumps and Smart Building Systems

A key advantage of electrically heated glass is its synergy with smart systems:

The BMS can monitor indoor dew point, humidity, and surface temperatures in real time.
Heated glass zones can activate only when needed—targeting rooms prone to condensation or thermal discomfort.
Smart coordination with heat pumps and ERVs (Energy Recovery Ventilators) ensures a holistic comfort strategywhile minimizing energy waste.

This system-wide optimization aligns with ASHRAE Guideline 36 (High-Performance Sequences of Operation for HVAC Systems), which promotes efficient, coordinated controls.

Effective R-Values That Match or Surpass Wall Insulation

Heated glass brings a dynamic boost to thermal envelope performance. While static R-values for windows typically underperform compared to walls, the active heating surface raises the effective R-value of glass in real-time conditions.

When radiant glass offsets internal heat loss, it creates an interior surface temperature on par with insulated walls, helping highly glazed buildings meet performance targets without sacrificing design intent.

A Smarter Path to Healthier, More Efficient Buildings

Electrically heated glass is more than a comfort upgrade—it’s a resilience tool for modern buildings. It:

Prevents mold and moisture buildup
Enhances occupant comfort without raising HVAC energy loads
Improves envelope performance to meet or exceed ASHRAE standards
Reduces visual clutter by eliminating bulky heating systems near windows
Supports decarbonization strategies by optimizing the performance of heat pumps and smart controls

Conclusion

Whether you’re designing a passive house, a luxury glass-walled home, or a commercial building seeking LEED or WELL certification, integrating electrically heated glass is a forward-thinking move. With its compatibility with ASHRAE 55, 62.1, 90.1, and Guideline 36, it helps deliver not only on energy and comfort goals—but also on health, durability, and design freedom.