#720: Whole House Dehumidification, Drippy Bath Fans, and Wet Cabin Walls

For complex HVAC systems in large homes, ensure clear documentation and training for homeowners, and consider involving manufacturers or specialized hydronic contractors for troubleshooting.

When designing whole-house dehumidification, anticipate unequal humidity distribution, especially across multiple floors or zones, and plan for dedicated ducting or zoned dehumidifiers rather than relying solely on equalization.

Insulate and air seal bath fan ductwork thoroughly, especially in unconditioned attics, to prevent condensation; consider insulated sleeves or custom-built insulated boxes around critical sections like elbows.

Avoid unvented propane heaters in enclosed living spaces as they introduce significant amounts of moisture, contributing to condensation and mold issues.

For new construction or major renovations, prioritize building science principles, including continuous air barriers and appropriate vapor control layers, to prevent moisture problems in wall assemblies, particularly in cold climates.

When dealing with severe moisture intrusion in wall cavities (e.g., from an unvented propane heater and poor wall assembly), complete removal of interior finishes and insulation is often necessary for proper drying and remediation, followed by rebuilding with appropriate vapor retarders and air sealing.

Two smaller, strategically placed and zoned HVAC/dehumidification units can often be more effective and provide better comfort control than one oversized central unit, especially in high-performance homes or those with multiple levels.