Attic ventilation at first glance may seem counter-intuitive: you insulate your home to reduce temperature fluctuations and save on utility bills, but then allow fresh air to flow through the attic no matter the time of year. However, the science behind attic ventilation is sound. Sealed attics trap excess heat and moisture, which can lead to reduced shingle life. And extra heat is not just a summer concern, come winter, hot attic air can melt snow on the roof during the day just to freeze when temperatures fall overnight, creating ice dams that lead to indoor leakage and roof damage. Ensure that your home has proper attic ventilation in accordance with these guidelines, however, you can save yourself from the stress and distress of an emergency roof repair by calling us and our experts will manage to resolve your problem.
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How Attic Ventilation Works
Attic ventilation is based on the principle that heated air rises naturally, primarily by using two types of vents:
- The intake vents, which are located at the lowest part of the roof below the eaves, allow cool air to enter the attic.
- Hot air exhaust vents, located at the top of the roof, allow hot air to escape.
Taking advantage of this natural process, referred to as passive ventilation, is the most common means of ventilation. In order to facilitate this exchange of warm and cool air, the general rule of thumb suggests the installation of at least 1 sqft.
The intake vents of the attic are most commonly installed directly in the soffit, either as individual vents spaced every few feet or as a continuous perforated soffit running along the entire length of the eave. While they are effective at pulling in cooler air, the biggest problem posed by this type of soffit vents is their positioning: homeowners can inadvertently block them when insulating the attic. Unfortunately, blocked soffit vents are just as bad as no soffit vents, because they prevent fresh air from flowing freely into the attic.
In addition to the multipurpose gable vents mentioned above, the release of all the heat that rises and gets trapped in the attic can be achieved with one or a combination of the three following vent models.
- Ridge vents, openings that run along the ridge along the entire length of your roof are often visible only to the trained eye. Hidden in plain sight and often camouflaged by specialty ridge shingles, these are particularly popular means of ventilation because they do not cause any disruption to the roofline. Installation of this type of attic ventilation involves leaving a gap in the sheath along the ridge and covering it with a perforated vent.
- Static vents often protrude from the roofline thanks to special covers designed to keep all precipitation rain, sleet, hail, and snow from entering the attic. Homeowners can choose from a variety of shapes and colors that match their shingles closely so that the vents do not appear out of place on the roof. One static vent style is the turbine vent, which uses the wind to power its enclosed fan, all it takes is a light breeze to rotate the blades and heat out of the attic. Again, whatever type of static vent, it must be located as close to the ridge as possible; homeowners concerned about how the addition might affect the curb appeal can only place them on the back of the roof to minimize visibility from the street.
- Finally, unlike the rest of these models that use passive ventilation, the electrical or solar-powered exhaust vents produce an effect similar to that of the turbine. The standard exhaust vent is switched on when the temperature inside the attic reaches the preset limit and runs until the temperature drops. While these powered vents effectively heat up, they will pull more cool air out of any air leaks in the ceiling of the house than the soffit vents simply because it’s easier. Considering that they already require a certain amount of electricity to power, additional energy spent on cooling the air conditioner in the entire house may make this type of ventless desirable, especially if your attic is not well-sealed.
Ventilating Finished Attics
With a square foot living space at a premium, many homeowners turn to their attics for a little extra room. When the attic becomes part of the home to be heated and cooled, the open-wall gable vents and roof vents are no longer feasible, but the underside of the roof (the sheathing and the rafters) can still get hot without airflow.
The answer is rafter venting. Rafter vents, or insulation baffles, are installed in any rafter space to create narrow gaps that direct fresh air from the soffit vents to the top of the roof.
How to determine whether you need better attic ventilation
Good attic ventilation reduces heat build-up in the summer. This reduces cooling costs and prolongs shingle life. In the winter, warm, moist air flows from the living space below into the attic. Good ventilation makes it possible for heat and moisture to escape. That keeps the attic dry and reduces the ice dams. Here are four signs of an unventilated or under-ventilated attic:
- Look at the roof and the eaves. If you don’t see any attic vents on the roof or on the eaves, you need to add some. Your roof vents may not look like the ones shown in this article. Your roof may have a low-profile, continuous roof air vent running along the top of the roof. Or it could have gable vents, which are louvered openings at the top of the gables.
- Touch the ceiling on a warm, sunny day. The hot ceiling tells you that the attic is acting like a solar oven, raising your bills of cooling and cooking shingles.
- Thick ice ridges on your eaves in winter are a sign of poor attic ventilation. The warm air that escapes from the rooms below is trapped in the attic. The snow melts and the water freezes on the cold eaves, creating ice dams.
- Warm air, which escapes from living space, also carries moisture that condenses on rafters or roof sheaths. Grab a flashlight and inspect the attic during the winter. You need better roof ventilation and some attic vents if you see dampness or frost.
Benefits of Proper Attic Ventilation
Here are some of the benefits of proper ventilation:
- It helps to reduce harmful moisture. Excessive moisture can build up in the attic, potentially damaging the structure and degrading the roofing system. It can lead to mold, too.
- It can help you save energy. Heat build-up in the attic comes at a cost, home air conditioning has to work harder to cool down the house, especially the living space below the attic.
- It helps prevent damage to the shingles of the roof. High attic heat can burn the shingle and cause it to age prematurely. In fact, most of the major shingle manufacturers strongly recommend proper attic ventilation for asphalt shingle installations.
- Prevent Ice Dams: While they might look very picturesque, the glaciers hanging along the edges of the roof are not something the homeowner wants to see. They are a sign of Ice Damming, a problem commonly associated with a heavily ventilated attic. If your attic keeps the hot air rising from below and gets too warm during the winter, your roof will heat up. This is going to cause the snow to melt on it. The resulting water will flow down to the edge of the roof and the gutter, where it is considerably cooler, and refreeze, building up as the cycle repeats with each new snowfall. At the end of the day, the water will back-up under the eaves and even into the attic.