Fungal spore transport through a building structure

Area of Science:

• Building science
• Environmental health engineering
• Aerosol science

Background:

• Building envelopes are critical for indoor air quality and energy efficiency.
• Understanding particle and spore penetration is vital for public health and building performance.
• Timber structures are common, but their airtightness and contaminant transport properties require investigation.

Purpose of the Study:

• To quantify the penetration of inert particles and fungal spores through a full-scale timber frame structure.
• To assess the influence of pressure differences and air leakage on contaminant transport.
• To evaluate the effectiveness of sealing and building pressure management in preventing penetration.

Main Methods:

• Laboratory measurements using a full-scale timber frame structure.
• Testing with inert particles (0.6-4.0 µm) and fungal spores (Penicillium, Cladosporium).
• Varying pressure differences across the structure and measuring air leakage.

Main Results:

• Penetration factors for inert particles ranged from 0.05-0.2 at moderate pressures.
• Fungal spores were found to penetrate the timber structure.
• Penetration was highly dependent on pressure difference, not surface holes; mineral wool contact was significant.
• Larger particles (4.0 µm) showed minimal penetration except via direct flow paths.

Conclusions:

• Sealing alone is insufficient to prevent fungal spore penetration through building envelopes.
• Building pressurization or balancing is the most effective method to prevent contaminant ingress.
• Mechanical exhaust ventilation requires careful consideration due to potential depressurization and health risks from building envelope contamination.