Proper Attic Ventilation

Proper attic ventilation is critical to the long-term performance of your roof as well as the attic space directly under it. Have you ever wondered why your attic smells musty? In many cases it is due to lack of proper ventilation. A properly ventilated attic can reduce cooling bills, extend shingle life and prevent mold growth, roof rot and ice dams in the winter.

How to determine if you need better attic ventilation

When an attic is properly ventilated it will reduce heat buildup during the summer months. That ostensibly reduces cooling costs and prolongs shingle life. In the winter, warm moist air seeps into the attic from the living space below. Good ventilation allows the heat and moisture to escape, keeping your attic dry.

 Where to place roof vents

For optimum results place roof vents near the roof’s peak and soffit vents in the eaves. Air flows through the soffit vents and out through the roof vents. There are many options available to provide adequate ventilation to your attic space, and no one solution works best for all situations.  Talk to a roofing professional to get the best ventilation solutions for your roof.

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Attic ventilation options:

Ridge Vent: This is a ventilation strip that is placed along the ridge line of the home. Prior to installing the ridge vent a 1” wide strip of roof decking is cut out along both sides of the ridge line to allow for air movement through the vent.

Soffit vents/insulation baffles: A critical part of installing any system of ventilation into your roof system is to make sure there is a point of entry and a point of exit for air flow. Review the soffit areas of your home for soffit vents. Soffit vents allow convective air movement from the soffits of the home to the ridge vent. Additionally,insulation baffles must be installed at the point where the attic floor meets the roof line to prevent the attic insulation from migrating into the cavities and restricting air flow from the soffit vents.

Whole house fans/attic fans: Fans and vents may be installed on the roof that will draw the air out of the attic space and exhaust it to the exterior. These fans may be controlled with a switch or a thermostat which detects heat build-up in the attic space and automatically exhausts the attic space. In some instances the fans can be set to activate when the humidity is too high (generally a cold weather setting).

Gable vents: These are installed in the gable ends of the home or building. They are usually louvered vents that allow air to be drawn out of the attic space, but prevent rain and snow from blowing into the attic space.

How many attic vents do you need? :  Determine your attic area by multiplying the length by the width. A 30 x 40 foot attic, for example, has an area of 1,200 square feet. Then aim for about 1 square foot (144 square inches) of vent openings per 150 square feet of attic. Building codes let you reduce that by half under some conditions, but more ventilation is usually better. The open area of a vent is sometimes listed on the vent as NFVA (net free vent area). If not, measure the size yourself. Roof vents will provide about half of the vent area and soffit vents the other half.

Mixed ventilation systems:  Many times we see older homes that have had new roofs installed with new improved ventilation (ridge/soffit system).  In many of these cases the old ventilation system (gable system) is left in place.  You might feel that 2 ventilation systems are better than one, however, the systems may actually interfere with each other causing a reduction in overall ventilation.  This can lead to moisture build up that results in attic mold growth.

In summary, proper roof ventilation can play a critical role in preserving the life of the roof and building performance, especially in light of ever-changing weather conditions. With the recommendations suggested here, durable, long-lasting roofs are well within reach.

Should you experience mold or water damage in your attic, contact the professionals at Burke Emergency Restoration.



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