– By Mark Mullins, Fabral Applications Engineer/Product Training Manager –
Ventilation is a critical contributor to the life cycle performance of a building. Pole barns and post-frame buildings can, in many cases, allow moisture to the interior of these buildings, usually caused by the moisture in the ground, contents and the fact that many of these buildings have no HVAC system. This moisture can cause condensation and premature deterioration of lumber, truss gusset plates, metal panels and more. In residential buildings, moisture stems from the human inhabitants and our daily activities—cooking, showering, even breathing. Gas heating can also contribute to the introduction of moisture.
Ventilating these structures is the most effective and economical method of removing moisture. This can be accomplished through the use of ridge venting materials which are placed directly between the ridge cap and the roof panels. The options are many, each serving to meet different functions:
- Some products are a spongy material that will expand and compress as needed to match the roof panel profile.
- Others are similar to solid foam closures with a portion of the solid section replaced with vent material.
- There are materials available that can be installed on top of closures to put the vent material out of the flow of wind-driven rain. The materials installed above the panel are typically more weatherproof and the eave is typically vented with the use of a vented soffit. For it to work properly, baffles can be used to ensure that insulation does not block the flow of air.
- Perforated panels may be used in lieu of vented soffit to allow a greater flow of air for larger buildings which is necessary to remove the moisture. Warm moisture-rich air rises naturally and escapes through the ridge vent. When this air exits, fresh dry air is drawn in through the vented soffit at the eave.
- A power fan on the roof can increase the flow of air while gable louvers and additional power fans work to draw air through the building.
- In homes that are “sealed up” and have no external venting, it is critical that moisture is removed. In these cases, the HVAC system circulates the air to remove the moisture.
Work with your manufacturer’s engineering department to determine the proper amount of venting and selection of the best products for your next project. Refer to the manufacturer for the proper installation procedures. The use and size of the building as well as type of construction are the typical factors to consider when determining your method and quantity of ventilation.
For more information on ventilation e-mail questions to Fabral.com/askMark.