What are the long-term thermal performance expectations for a curtain wall in humid climates?

In humid climates the long-term thermal performance of a curtain wall is governed by glazing specification, frame thermal breaks, insulation strategy, and moisture management. Expect initial thermal resistance (U-value) to be defined by the chosen glazing unit and frame — for example, a double-glazed unit with low-E coating and argon fill typically delivers a substantially lower U-value than single glazing. Over the operational life of the façade, several factors can degrade thermal performance if not properly addressed: sealant ageing, spacer corrosion, gas diffusion out of IGUs, and accumulation of moisture in framing cavities. Metal curtain wall systems must use engineered thermal breaks and continuous insulation to reduce conductive heat gain through frames. In humid climates, vapour drive is a significant concern; without proper vapour barriers and pressure equalisation/dry drainage strategies, moisture can condense inside assemblies or degrade insulating materials, producing lower effective R-values and risk of mould. Designers should specify IGUs with warm edge spacers and desiccant, robust silicone or polyurethane edge seals rated for long service life, and frames fabricated from aluminium with integral polyamide thermal breaks sized for expected temperature gradients. Regular maintenance of gaskets and resealing of joints mitigates long-term degradation. Performance expectations should be set in terms of measurable metrics: maintain design U-value within 10–15% of as-installed baseline over a 20-year period and preserve air leakage and water penetration performance to specified thresholds. Project documentation must include condensation risk analysis, hygrothermal modelling for local climate, and maintenance schedules. For metal curtain walls installed in coastal or high-humidity urban environments, add corrosion-resistant finishes and specify ventilation/drainage details to ensure long-term thermal stability and occupant comfort.