The Importance of Above Sheathing Ventilation

By Anna Lockhart.  

Above Sheathing Ventilation (ASV) is an often-overlooked method of keeping the roof cool. Here’s why your crew should consider using ASV in roof cooling.  

Above sheathing ventilation (ASV) is a method of home ventilation in which the air space between the roof cladding material, the subassembly and the roof deck is ventilated. This ventilation method allows the temperature of the roof cladding to maintain a similar temperature with that of the outdoors, reducing heat levels and maintaining a reasonable temperature during warm weather and summer seasons.  

The Metal Construction Association (MCA) has put together a report detailing the engineering and science behind this method of ventilation, highlighting the importance and benefits such a system can offer homeowners and building owners living in warmer climates. The MCA points out many important factors to consider, such as the fact that roofs experience a much higher temperature fluctuation than any other surface, and ventilation is key in regulating this concern.  

By ventilating the air space between the roofing material layers in an ASV design, the roof cladding temperature is allowed to be closer to the outdoor ambient temperature, which in turn reduces the amount of heat gained and retained within the insulation and home. The design of an ASV system has also been shown to reduce the amount of moisture retained within the roof, preventing rot and rust, while also giving the structure an added advantage of resistance to fire in areas where wildfires are common.  

To maximize the performance of an ASV system, homeowners and building owners can combine the ASV system with a cool roof coating to maximize the benefits of both solutions; cool roof coatings work similarly to ASV in that they reduce the surface temperature of a roof. By layering the two solutions, owners are getting the best possible benefits and cooling solutions.  

Read the full report to learn more about the design, functions and benefits of using an above sheathing ventilation system.