Predicting Condensation Performance of Custom-designed Curtain Wall

摘要

Condensation will occur in any interior surface that falls below the dewpoint-or, the temperature at which airborne moisture (water vapor) turns into a liquid-of the interior ambient air, which is also dependent on relative humidity (RH). Generally, the greater the indoor-outdoor temperature difference, the more likely condensation is to form, particularly when higher levels of moisture are present. If the dewpoint is below 0 C (32 F), the condensation can be in the form of frost or even ice. The challenge to minimize condensation is thus to lower the indoor humidity and/or keep the inside surface temperature of the glass and frame above the dewpoint temperature, especially when outdoor temperatures are frigid. Most design features that improve thermal performance (i.e. decrease U-factor) also improve condensation resistance, although there can be inherent trade-offs with other design features. Some features that typically improve both U-factor and condensation resistance rating include: 1. multiple-cavity insulating glass (IG); 2. low-emissivity (low-e) coatings within the IG cavity; 3. warm-edge IG spacers; 4. insulating fill gas, such as argon; and 5. lower thermal conductivity frame materials or design. This mission to reduce indoor condensation is complicated by many variables that may affect interior surface temperatures and thus affect the potential for condensation. These may include, for example, the following.