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Substrate Vulnerability Index (SVI)
SYS
The Substrate Vulnerability Index (SVI) quantifies how susceptible a building material is to colonisation and degradation — the 'material host' half of the risk equation. It is a composite of measurable properties: porosity (%), pH sensitivity, mineral composition (e.g. ferrous content in Z1 ironstone zones), hydrophobicity/hydrophilicity, surface roughness (Ra) and, for polymers, glass-transition temperature (Tg). Within COSMOS the SVI combines with organism aggressiveness through the interaction term (BEMCE_org × BEMCE_sub), which defines biophysical conflict intensity — risk rises exponentially when an aggressive organism meets a vulnerable substrate. The SVI is what lets the engine treat soft Cornbrash limestone, porous render and engineering brick as quantitatively different cleaning problems rather than one generic surface.
capillary absorption, surface free energy
The Substrate Vulnerability Index (SVI) quantifies how susceptible a building material is to colonisation and degradation — the 'material host' half of the risk equation. It is a composite of measurable properties: porosity (%), pH sensitivity, mineral composition (e.g. ferrous content in Z1 ironstone zones), hydrophobicity/hydrophilicity, surface roughness (Ra) and, for polymers, glass-transition temperature (Tg). Within COSMOS the SVI combines with organism aggressiveness through the interaction term (BEMCE_org × BEMCE_sub), which defines biophysical conflict intensity — risk rises exponentially when an aggressive organism meets a vulnerable substrate. The SVI is what lets the engine treat soft Cornbrash limestone, porous render and engineering brick as quantitatively different cleaning problems rather than one generic surface.
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