Properly sizing and placing intake and exhaust vents for a PVC roof system is crucial for maintaining good ventilation and preventing moisture buildup. Intake vents, usually located at the eaves or soffits, allow fresh air to enter the attic space. Exhaust vents, placed near the roof ridge or high points, let out warm, moist air. The general rule of thumb is to provide balanced ventilation with about equal intake and exhaust areas. For PVC roofs, the total net free ventilation area should typically be about 1/150th of the attic floor space when balanced, or 1/300th if using a vapor barrier. Poorly sized or placed vents can lead to condensation issues that can damage the roof membrane or insulation. You can estimate your ventilation needs by measuring the attic floor area and multiplying by appropriate fractions, but always check local codes and roofing manufacturer guidelines for specifics as they can vary.
A simple DIY check you can do involves visually inspecting your attic for airflow and moisture problems. On a windy day, you should feel air movement near soffit and ridge vents, and there should be no signs of mold, staining, or damp insulation. Using a moisture meter can help detect hidden wet spots. If you notice any issues like excessive heat in the attic or damp insulation, consider calling a roofer with experience in PVC roofing. When inviting a contractor for an evaluation, ask how they determine the correct vent sizing and whether their recommendations follow the PVC membrane warranty requirements. Also inquire about how they ensure vent placement won’t interfere with the roof system’s integrity or lead to leaks, as improper installation can void warranties. Keeping these points in mind can help you maintain a durable, problem-free PVC roof.