Module 4: Structural & Thermal Performance Analysis 

1. Structural Surveying of Fenestration Systems

Wind Load Resistance & Deflection Limits

• Design Standards:

• Calculated per BS EN 1991-1-4 (Eurocode 1: Wind Actions) and CWCT (Centre for Window & Cladding Technology) guidelines.

• Typical requirements:

• Residential windows: ≤ 1.5 kN/m² wind load (moderate exposure).

• High-rise curtain walls: ≤ 3.0 kN/m² (severe exposure).

• Deflection Limits:

• Maximum permitted deflection = L/175 (where L = span length).

• Excessive deflection causes:

• Glass stress cracks.

• Sealant failure (due to frame movement).

Anchorage & Fixing Inspections

• Common Fixing Types:

• Mechanical Anchors: Through-bolts, expansion sleeves (check for corrosion).

• Chemical Anchors: Resin-fixed studs (verify cure time compliance).

• Inspection Checklist:

• Correct spacing (≤600mm centres for heavy glazing).

• No over-tightening (distorts frames).

• Stainless steel fixings (A2/A4 grade to prevent rust).

2. Thermal Bridging & Condensation Risk

Identifying Cold Bridges

• Problem Areas:

• Frame Junctions: Where aluminium meets masonry (Ψ-value > 0.15 W/m·K = poor).

• Spacer Bars: Metal spacers in double glazing (conduct heat outward).

• Detection Methods:

• Thermal Imaging: Shows temperature differentials (cold spots = risk zones).

• Condensation Mapping: Interior moisture indicates thermal weak points.

Mitigation Strategies

3. Energy Efficiency & Retrofit Solutions

Upgrading Historic Buildings

• Secondary Glazing:

• Adds airtight layer without altering original windows.

• Achieves U-value ≤1.8 W/m²K (vs. single glazing’s 5.0 W/m²K).

• Slim-Profile Systems:

• Minimalist double glazing (e.g., 6mm overall thickness) for listed buildings.

• Uses low-iron glass to maintain aesthetic.

Modern Retrofit Techniques

• Vacuum Glazing:

• Ultra-thin (6mm) with U-values ≤0.7 W/m²K.

• Ideal where frame depth cannot be modified.

• Dynamic Glazing:

• Electrochromic/thermochromic glass adjusts solar gain (G-value 0.1–0.5).

Key Takeaways

• Structural Failures often stem from under-specification (wind loads) or poor fixings (corrosion).

• Thermal Bridges account for 15–30% of heat loss; solutions must target frame and glazing.

• Retrofits balance heritage constraints with modern performance needs (slim profiles/vacuum glazing).