Roof and Attic Ventilation in Winter

When we talk about roof and attic ventilation, most people think of the air flow needed to release hot air within attics on hot summer days. But proper roof ventilation is important in the winter as well as in summer. This is especially true in Lakewood, Arvada and the Jefferson County area where summers are hot and winters can be long and cold.

Condensation in the Attic

roof attic ventilation winter louver box turtle vents

Louver, Box or Turtle Vents

In the winter, moist warm air rises up from the home’s living space into the attic. Showers, cooking and even humidifiers create moisture in the house that naturally rises up to the attic. Even if there is a vapor barrier in place, it still cannot totally stop this process. If the moisture is not properly vented from the attic, as the moisture cools, it condenses as water droplets. This condensation drips on the insulation below and will eventually seep into the ceiling material. Over time the condensation will ruin the insulation and damage the ceiling. The accumulated moisture in the attic can also cause wood rot, mold and swell the deck causing waviness and buckling of the deck and shingles.

Ice Dams in Jefferson County

Ice dams are another winter problem due to poor ventilation. During winter months in Jefferson County heat can build up in poorly ventilated attics. Heat builds up because there is not enough insulation and not enough air exchange to release the heat. This stagnant heat causes the underside of the roof deck to be warmer than the outside temperature. Snow piled up on the roof will then start to melt under the snow and then refreeze at to the eaves and gutters. Snow and ice build up at the edge and the rest of the flowing water backs up under the shingles and fascia. See our article on ice dams for more information on how to avoid this winter damage.

Different Types of Attic Ventilation

roof attic ventilation winter gable vent

Gable Vents

As explained above, improper roof ventilation can cause damage to the property inside and out. On the flip side, proper roof ventilation can reduce energy consumption, keep the house environment more comfortable, and protect roofing materials and the building structure. The first thing proper ventilation needs is a balance between the intake and outtake of air. It also needs enough vents per square feet with the vents installed in the most efficient locations. A balanced air flow will have the same amount of intake per square foot as outtake in order to release all of the heat and moisture. There also needs to be a certain number of vents based on the square footage of the attic. A common rule across most residential building codes calls for 1 square foot of vented area for every 300 square feet of attic space with a vapor barrier. Without a vapor barrier the venting should be 1 square foot of vented area for every 150 square feet of attic space.

In addition to the balanced air flow and number of vents, the location of the vents is key. The two main ventilation components are intake vents and exhaust vents. There needs to be an equal amount of each for efficient air flow. Intake vents work best at the roof’s edge or under the eaves (soffits). There needs to be an even number of soffit or drip edge vents on each side of the house. The cooler air comes in at the bottom and pushes the hot air up and out. There are a variety of intake vents: under eave vents, continuous soffit vents, vented drip edge and vented soffit vents to name a few.

Exhaust vents need to perform two main tasks: allow an efficient outflow of air and prevent snow and rain from entering the attic. The most efficient exhaust vent is the ridge vent. This provides continuous and uniform air movement across the full length of the roof. Other exhaust vents include: roof louvers, gable louvers, wind turbines and power attic ventilators.

Mixing Ventilation Types

There are a lot of choices when it comes to ventilation, and different types of exhaust vents should not be mixed. Mixing ventilation types will diminish the ventilation effectiveness and increase the chance of weather elements entering the attic. Call Rock’s Roofing, Inc. for a free assessment of your roof and the ventilation system. We have been installing roofs in Jefferson County, CO and surrounding cities since 1968. We know roofs and ventilation.