Technical Methodology & Compliance Statement

The tool calculates thermal transmittance (U-values) for building elements using a multi-standard approach based on the specific construction type:

• Standard Masonry and Timber Frame (BS EN ISO 6946): For standard walls and roofs, the engine utilizes the thermal resistance method (R = d/λ). It correctly accounts for surface resistances (R_si and R_se) adjusted for the direction of heat flow.
• Inhomogeneous Layers & Repeating Bridges (The "Combined Method"): For elements containing repeating thermal bridges (such as timber studs, SFS metal studs, or roof joists), the tool implements the ISO 6946 Combined Method. This calculates the arithmetic mean of the Upper Limit (parallel path method) and the Lower Limit (isothermal planes method).
• Ground-Bearing Floors (BS EN ISO 13370): Floor calculations utilize the characteristic dimension of the floor (B') and equivalent thickness (d_t) calculations, accounting for the thermal influence of the ground.
• Thermal Bridge Corrections: The engine allows for the inclusion of point thermal bridges (BS EN ISO 6946 Annex F), accounting for mechanical fasteners and brick ties using χ-value (Chi) corrections.

Moisture assessment is performed through a detailed steady-state analysis, moving beyond simple static checks:

• The Glaser Method (BS EN ISO 13788): Interstitial condensation risk is assessed by calculating temperature gradients and vapour pressure profiles. By comparing the calculated vapour pressure (P) against the saturation vapour pressure (P_sat), the engine identifies precisely where and when condensation may occur.
• Surface Condensation & Mold Risk (f_Rsi): In accordance with ISO 13788, the tool calculates the Temperature Factor at the internal surface (f_Rsi). The engine flags a warning if the factor falls below the standard threshold (typically 0.75).
• Annual Monthly Assessment: The tool performs a monthly analysis utilizing regional climate data to simulate performance throughout a standard meteorological year, identifying seasonal drying potentials.