The study of the microclimate is a fundamental prerequisite of cultural heritage restoration
strategy, as the durability of the interventions strongly depends on the environmental conditions.
Before the restoration of the frescoes of the apse, seriously degraded, the microclimate in the
Capilla Mayor of the Santiago de Compostela Cathedral was monitored continuously for one
year to assess the main environmental risks and elaborate a preventive conservation plan.
The main natural and anthropic factors affecting the microclimate of the Capilla were
identified, as well as their relevance and the associated risk of damage to the frescoes. In
particular, the thermo-hygrometric values measured close to the vault were not fully in
compliance with respect to the ranges indicated in literature for the conservation of the
frescoes. Finally, solutions were suggested to improve the environmental conditions in the
Capilla, thus reducing further damage and enhancing the durability of the frescoes after the
planned restoration.