Roof systems can do more than simply protect a home from the elements. By venting an attic, they can also help prevent ice dams in winter and provide indoor air comfort in summer.
In many parts of the country, roof ventilation is especially critical in the winter, when attic air under a roof becomes warmer than the air outside (this is almost always an insulation and attic air-sealing problem). The warm roof allows snow to melt. The melted snow can then travel to the eaves, where it can re-freeze and back up under shingles, producing ice dams. Venting, however, keeps the roof colder, helping prevent the snow from melting and contributing to ice dams.
But ventilation plays an important part in the summer, too. An unvented roof makes a home hotter and harder to cool. Venting allows hot air to escape, helping to keep the overall house cooler, lowering energy costs, and reducing roof deterioration. Venting the roof also reduces indoor temperature extremes in the summer, keeping upper and lower floors at a more even temperature.
Most importantly, ventilation allows built-up moisture to escape. This reduces condensation, which lessens the risk of mold, mildew, and fungus growth and, in turn, minimizes the likelihood of wood rot. Moisture escape is the primary reason building codes require roof ventilation (unless the roof meets the requirements for a sealed attic).
Here’s how roof ventilation works. Air enters the roof through soffit vents. As it warms up, it rises to the top of the attic, where vents at the ridge of the roof (where the two sides met at the top) provide the warmer air with a natural exhaust point.
Proper ventilation is an integral part of a roofing system and part of why it’s required by many building codes. It’s comprised of six main elements, each of which provides important benefits:
Ice Barrier Membrane. This self-adhesive layer protects the roof substrate from ice dams.
Underlayment. A water-resistant barrier, it provides additional protection from condensation and severe weather.
Roof Panel. These steel panels deliver a design touch along with exceptional resistance to weather hazards.
Soffit Vents. This is where air enters at the eaves. These intake vents placed at the lower roof edges are critical to providing cross ventilation.
Ridge Vent. This is where hot air escapes, preventing snow melt and ice dams in the winter and decreasing cooling costs in the summer.
Ridge Cap. Installed over the ridge vent itself, this provides an aesthetically pleasing finishing touch.
Learn more about the benefits of metal roofing and ventilation from ProVia.