GFRG is typically an indoor material. It is not typically subjected to extreme thermal cycles, at least not in the same way as a traditional exterior façade. Yet, as the weather warms, there are still likely to be temperature fluctuations from poorly functioning HVAC systems, indoor equipment, and more. How well can GFRG be expected to withstand these cycles?
Luckily, due to its gypsum core, GFRG performs extremely well within expected temperature ranges. Installation quality matters, but GFRG is a often able to withstand cosmetic cracking.
About Indoor Cycling
Typically, we don’t expect indoor ambient temperature to change nearly as much as outdoor temperature. At most, we expect smaller, more frequent swings (e.g., 2-8°C/5-15°F) driven by operational factors.
Still, systems break down. HVAC costs can be substantial. Aging properties may have trouble cooling or withstanding the expected 100+ degree heat in some areas.
What is the magnitude and frequency of temperature change that an interior GFRG assembly can withstand without compromising its aesthetic or structural integrity?
Thermal Behavior of GFRG in Interior Environments
Glass Fiber Reinforced Gypsum (GFRG) performs well under normal interior temperature variations because its base material, gypsum, is dimensionally stable within moderate ranges. The glass fibers within the composite further improve its resistance to cracking and deformation caused by small shifts in temperature or humidity.
In most commercial and residential environments, temperature swings rarely exceed 10–15°F (5–8°C) over short periods, even when HVAC systems cycle off temporarily. Within this range, GFRG maintains dimensional stability. The material’s coefficient of thermal expansion is low – typically in the range of 0.01 to 0.02 mm/m·°C – meaning that even a 10°C (18°F) change over a 3-meter panel would result in less than 1 mm of movement. For most installations, this is well within tolerance, particularly when proper expansion joints or flexible sealants are incorporated at connections.
When Temperature Fluctuations Become a Problem
The risk to GFRG assemblies comes not from moderate temperature swings but from repeated or sustained extremes that create differential movement between materials. For instance, if GFRG is mounted directly against metal framing or structural members that expand and contract more significantly, the difference in movement can place shear stress on fasteners or joints.
In practice, this type of stress might lead to:
- Hairline surface cracking near joint lines or mechanical connections
- Minor separation at seams if flexible joint compounds were not used
- Surface distortions in thin panels that lack proper backing or reinforcement
The good news is that these issues are largely cosmetic and can usually be mitigated through correct installation methods – including proper joint treatment, mechanical isolation, and the use of compatible substrates.
Influence of Humidity and Air Conditioning
Thermal cycling is rarely an isolated factor indoors. Fluctuations in humidity often occur alongside changes in temperature, particularly in poorly conditioned spaces or near HVAC outlets. While GFRG itself is non-hygroscopic compared to plain gypsum plaster, extended exposure to high humidity can cause surface coating expansion or slight dimensional changes in the gypsum matrix.
Prolonged operation of air conditioning systems, especially in humid climates, can also create localized cooling zones where condensation forms on surfaces. If this moisture interacts with unsealed GFRG edges or joints, it can cause surface chalking or microcracking over time. For this reason, interior GFRG should always be sealed, primed, or finished with appropriate protective coatings in areas exposed to frequent environmental fluctuations.
Practical Guidelines for Designers and Installers
Under most interior conditions, GFRG does not experience any significant structural degradation due to thermal cycling. To ensure long-term performance:
- Maintain interior temperatures between 60°F and 90°F (15°C to 32°C) wherever possible.
- Avoid direct installation against materials with very different coefficients of expansion (such as metal framing) without proper isolation.
- Use flexible joint compounds and finishes that can accommodate small dimensional shifts.
- Ensure that HVAC and dehumidification systems remain operational in extreme climates, particularly during seasonal shutdowns or renovations.
When these guidelines are followed, GFRG can reliably maintain its visual and dimensional integrity even in buildings that experience daily or seasonal indoor temperature cycling.
Performance Summary
GFRG’s performance under thermal cycling is stable within all reasonable indoor conditions. While repeated or excessive thermal and humidity swings may lead to superficial cosmetic effects, structural integrity remains largely unaffected.
Proper installation, environmental control, and finishing practices ensure that GFRG retains its form, finish, and appearance over decades of use – even in interiors with variable temperature control or aging HVAC infrastructure.