Managing Condensation Inside Your Fabric Building

Condensation is one of the most common questions fabric building owners ask about, and understanding why it happens and how to manage it keeps your stored goods in better condition and extends the building’s service life.

Why Condensation Forms

Condensation occurs when warm, moist air contacts a cooler surface. In a fabric building, this happens most frequently during spring and fall when daytime heating warms the air inside the building, then evening cooling drops the cover temperature below the dew point of that warmer interior air. The result is water droplets forming on the underside of the PVC cover.

This is the same process that creates morning dew on your vehicle windshield — and the solution follows the same principles.

Ventilation Is the Primary Solution

Moving air prevents moisture from concentrating at the cover surface. Open-ended buildings naturally ventilate through the chimney effect — warm air rises to the peak and exits while cooler air enters at the base. Even partial end wall openings provide enough air exchange to significantly reduce condensation.

For fully enclosed buildings, adding ridge vents or upper sidewall ventilation panels allows the warmest, most moisture-laden air to escape from the highest point in the building where it naturally accumulates.

Ground Moisture Control

Moisture evaporating from the ground beneath the building is a major source of interior humidity. A compacted gravel floor reduces ground moisture contribution compared to bare earth, and adding a polyethylene vapour barrier beneath the gravel virtually eliminates ground-source moisture.

For buildings on clay-heavy soils — common in the Edmonton area — ground moisture control is especially important because clay holds and slowly releases moisture over extended periods.

Contents That Contribute Moisture

Fresh hay, green lumber, and recently washed equipment all release moisture inside the building. Hay that is baled at proper moisture content (below 18 percent for small squares, below 16 percent for rounds) still releases some moisture as it cures in storage. Allow adequate airflow around hay stacks — leave space between bales and walls — so this moisture can dissipate rather than accumulating.

When Condensation Is Acceptable

Some condensation during temperature transitions is normal and not a cause for concern. Light morning condensation that evaporates within a few hours as the day warms is typical and does not damage the building or most stored goods. The concern arises when condensation is persistent, heavy, or dripping onto sensitive stored items.

If you are storing equipment, vehicles, or other items that are not damaged by occasional light moisture, normal condensation levels in a well-ventilated building require no action. If you are storing moisture-sensitive goods like electronics, paper products, or finished wood, managing condensation through ventilation and ground moisture control becomes more important.

Frequently Asked Questions

Can fabric buildings store hay effectively?

Fabric buildings are one of the most cost-effective ways to store hay. The PVC cover keeps rain and snow off your bales while allowing enough air circulation to prevent mould growth. Studies show that covered hay retains 95%+ of its nutritional value compared to outdoor-stored hay that can lose 25–35% to weathering. The ROI on covered storage often pays for the building within 2–3 seasons.

What size building do I need for hay storage?

Sizing depends on bale size and stacking method. For large round bales (5'×5'), you can fit approximately 3 bales per 100 square feet when stacked in rows. A 40'×60' building (2,400 sq ft) stores roughly 70–80 large round bales. For small square bales stacked high, you can store significantly more per square foot. Contact MAX for a sizing consultation based on your specific needs.

How do I prevent moisture in a fabric hay storage building?

Proper moisture management starts with site preparation: ensure your gravel pad has adequate drainage slope (2% minimum) away from the building. Stack bales on pallets or a gravel base — never directly on bare ground. Configure end walls for cross-ventilation to allow moisture to escape. In humid climates, leaving one end partially open provides excellent airflow without compromising weather protection.