TOPICS: Homeowner Ventilation

POSTED BY: JODY CRUM             May 1, 2023

Even though the attic is situated at the highest level of a house, it often becomes the focal point of ventilation problems concerning the roof. The absence of conditioning in the attic results in persistent issues of moisture and heat. Excessive humidity or heat can cause various problems ranging from reduced comfort and increased utility bills to leaks within the house.

By enlightening homeowners about the significance of ventilation and elucidating how a well-regulated airflow in the attic safeguards their roofing investment, a contractor can distinguish their business and protect the homeowner’s roofing investment. Conducting an inspection of a home’s attic can help identify ventilation issues that may compromise comfort, escalate energy bills, or even shorten the lifespan of the roof.

Homeowner Communication

Highlighting the significance of proper airflow helps customers understand the importance of ventilation. Although inadequate ventilation may not immediately cause any urgent issues, it can persist and eventually lead to inconvenience and expenses. Poor attic ventilation, much like leaky plumbing, can gradually erode a home’s comfort and diminish the roof’s performance through various issues as described below.

In warm months, particularly in Southern regions, excessive daytime heat in the attic can cause the roof shingles to bake from underneath. As the temperature drops at night, contraction may result in bumps underneath the shingle or curled edges. The physics of air movement, from warm to cold, can also affect comfort inside the house and reduce energy efficiency. As the heat in the attic builds up, the warmer air will naturally move towards the cooler parts of the house. This, in turn, can cause the cooling equipment to work harder, increasing energy costs.

The problems associated with poor ventilation are not limited to summer. During winter, insufficient ventilation can lead to a thaw-and-freeze cycle as snow on the roof above a warm attic melts and refreezes along the roof eave. Icicles hanging from a roof are often a telltale sign of ice damming, which can potentially result in water intrusion.

Indoor activities such as cooking, showering, and watering plants can introduce moisture into the indoor air. Homeowners should ensure that fan hoses in areas such as bathrooms are vented outdoors rather than into the attic, where they can cause additional moisture problems. Sometimes, homeowners’ good intentions can unintentionally lead to issues. For instance, adding insulation in the attic may block existing intake ventilation, hampering future airflow.

While insulation is typically appreciated for its thermal performance and its role in maintaining living areas’ comfort, it also plays a crucial role in unconditioned attic space. It aims to maintain a temperature that closely aligns with the outdoor temperature and humidity. Striking a balance between the external environment and the attic space will help prevent issues like shingles becoming too hot from overheated attics or excess moisture leading to condensation.

Home Design and Climate Considerations

In modern homes, ventilation is typically sufficient. However, in older homes, especially those built before codes regarding attic ventilation were established, improving attic airflow may be necessary.

While building codes vary by location, a general guideline is to have one square foot of net free vent area for every 150 square feet of attic space. The more complex a roof’s design, with more pitches and intersections, the more challenging it can be to ensure proper attic airflow. Simple, gable-style roofs are generally the easiest to ventilate, but they are less popular among today’s home design trends.

The objective of attic ventilation is to achieve a 50/50 balance between air intake and exhaust. With passive ventilation, intake vents should be placed under the eaves to allow outside air to flow in and then exit through the roof’s peak. Factors such as a home’s location, orientation, and wind direction can all impact ventilation and should be taken into account when installing vents. If the ventilation system is unbalanced, air pressure can cause outside air to enter through the exhaust vent and exit through the intake vent, short-circuiting the intended airflow. A ventilation system should be set up with 40-50% exhaust ventilation to ensure proper pressure, allowing air to flow in through the intake vents and out through the exhaust vents even during high wind conditions.

Warning Signs

If there is mold, rotting wood, or rust on fasteners inside the attic, it may be a sign that the humidity levels in the attic are not consistent with the outdoor conditions. Other signs of heat and moisture problems in the attic include curled or warped shingles visible from the street. It is always advisable to check the ventilation system if the temperature and humidity in the attic are significantly different from the outside conditions.

During an attic inspection, it’s essential to ensure that intake ventilation under eaves allows air to flow upward, and exhaust ventilation is visible, indicating a path for air to pass through. To determine the right vents for the job, it’s crucial to use online tools, such as apps and roof calculators, that can perform quick calculations that consider the requirements of different products. As various products have different net-free vent areas, which is the measure of how much air can pass through unobstructed, it’s crucial to choose the right vents.

Sharing real-world examples of ventilation issues can help establish credibility with homeowners. For instance, a contractor can explain how fixing a ventilation problem helped reduce energy bills in a home with a similar issue. The ultimate goal when planning for ventilation is to keep moisture and heat out of the attic.

About the author: Jody Crum is CEO of Alliance Specialty Contractor. For more information, visit aspecialtyc.com.