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Use Above-Sheathing Ventilation for a Better Roof

A Better Roof
You may have heard that roof and attic ventilation are critical aspects of keeping your roof healthy. But have you heard about sheathing ventilation? This refers to an air gap between the roofing material itself and the roof deck that supports it. Not all roofs have this type of ventilation, but homeowners across most of the country could benefit from its addition.

Here are the basics of sheathing ventilation (also called above-sheathing ventilation or ASV) and how it can improve your roof's performance.

What Is Above-Sheathing Ventilation?

Sheathing is the roof deck, that is, the lowest level of your roof. Sheathing is the plywood you can see between the rafters in your attic. So above-sheathing ventilation is ventilation above the sheathing, between the layers of the roof.

Metal and tile roofs often have natural sheathing ventilation due to their shape and how they're installed. But ASV can be added to many roof installations with a process called battening. This process involves layering wooden strips (battens) in first one direction, then the other, to create a crosshatched scaffolding two strips of wood deep.

This structure is then used to support the roofing material, rather than applying the roofing material straight to the roof deck. The battens are placed far enough apart that air can circulate freely under the roof's outer layer. If you want to do this with asphalt roofing, you may need to place a second roof deck above the battens.

Why Is This Better Than Attic Ventilation?

Sheathing ventilation is not a replacement for attic ventilation. However, sheathing ventilation has a unique ability to reduce heat transfer to and from your attic even if you already have excellent attic ventilation. That's because sheathing ventilation adds an extra layer of defense against the outside world.

Attic ventilation is still necessary. Without it, the moisture in the attic air will condense against the underside of the roof deck rather than escaping harmlessly into the outside air.

How Does Sheathing Ventilation Save Money?

Sheathing ventilation saves money by saving energy. ASV does this in a similar fashion to double-glazed windows. Double-glazed windows aren't more energy-efficient because they have a greater thickness of glass. These windows have efficiency because the gap between the two panes slows down heat transfer.

Although sheathing ventilation doesn't block heat as much as a double-glazed window because it uses regular air rather than a gas, sheathing ventilation is still capable of saving you money throughout the year. ASV is effective at keeping heat out in summer and has a buffering effect in winter as well.

ASV can also save money by preventing ice dam leaks. That's because when heat does escape from your attic, the extra ventilation helps direct the warmer air up to the ridge vents rather than through the outer roof layer. This helps to keep the outside surface of your roof cold in winter, so the bottom layer of snow doesn't melt, run down to the gutter, and freeze into a dam.

Is Sheathing Ventilation for Everyone?

Choosing a replacement roofing material that has a natural air buffer zone (such as clay tile or certain types of metal roof) may be the easiest way to implement the benefits of sheathing ventilation. However, ASV is certainly not something you'll want to add to an existing roof. You can't slip an air space underneath a roof you already have, so adding it would require paying for a new roof installation.

However, if you're considering replacing your roof in the near future, consider the cost-benefit balance of utilizing sheathing ventilation. Whether that means having your new roof constructed with a batten system or simply choosing clay tile that lets air flow underneath, you can reap the rewards of a better-insulated roof.

These basics show how an above-sheathing ventilation system can help your roof save energy and protect your roof from catastrophic ice dams. Get in touch with Hayco Roofing today to learn more about roofs with above-sheathing ventilation. We have plenty of metal and clay tile roofing options available to choose from.