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attic ventilation

The attic space under your roof can serve many useful purposes. Finished attics offer additional living areas for bedrooms, offices or playrooms. Partially finished or unfinished attics can be used as storage areas or locations for limited occupancy or practical use. Whatever the purpose you assign to the attic, you must make sure that the space has sufficient amounts of attic ventilation. Without enough ventilation, the environment in your attic can severely damage the roof and the framework of your home. Poor attic ventilation can also cause other preventable problems that can cost you time, money and aggravation.

Here's an overview of the troubles that can occur without proper attic ventilation and what you can do to solve the problem before it results in expensive structural damage or loss of belongings.

The Need for Attic Ventilation

There are two main problem areas that result from inadequately ventilated attic spaces:

  1. Heat: As sunlight beats down on the roof of your home during the summer, attic spaces underneath can get extremely hot. It's not uncommon for unfinished attics to reach temperatures of 150 degrees or more. This results in a large volume of overheated air that can cause damage to your home's structure and drive up monthly energy bills. Temperatures this high can make an attic uninhabitable by people or pets and, in many cases, unsuitable even for temporary storage of belongings, especially anything that could be damaged by heat.
  2. Moisture: Unventilated or poorly ventilated attics are also liable to accumulate large amounts of moisture. This moisture comes mostly from condensation of humidity in the environment but can also come from moisture-producing activities inside your home, such as dishwashing, cooking, showering or clothes drying. Without ventilation, sufficient amounts of moisture can accumulate to make the attic damp enough to cause damage to the physical structure of your home or to items kept in the attic.

Consequences of Poor Attic Ventilation

Poor attic ventilation can lead to significant and expensive troubles with the roof of your home. The two most common roof-related problems are:

  1. Roof shingle damage: When the attic areas under the roof shingles get hot, the asphalt material of the shingles themselves can start to melt. This can cause the shingles to fail, producing areas where rainwater leaks, energy is lost or similar problems can occur. In some cases, manufacturers may not honor warranties on shingles that incur damage because of inadequate attic ventilation.
  2. Roof truss damage: Excess heat and moisture can cause roof trusses and the upper framework of your home to warp or rot. If trusses or framing boards become sufficiently damaged, there's no choice but to replace them, which is an expensive undertaking that requires professional assistance. Even worse, you and your family may have to temporarily move elsewhere until repairs are made and the truss replacement is finished.

Insufficient attic ventilation can also lead to other serious problems that include:

  • Reduced insulation effectiveness: Insulation in your home's attic and walls helps make the space more energy efficient and comfortable. The purpose of insulation is to restrict the movement of heat from warmer areas to cooler ones. If insulation gets damp or wet, it will no longer work properly, reducing the effectiveness of HVAC equipment and making your home's interior less comfortable. Wet insulation will likely need to be replaced, which is an unnecessary expense that could be prevented.
  • Growth of harmful mold and mildew: Too much moisture in the attic can also cause mold and mildew to grow on surfaces throughout the area. These substances are potentially harmful to health and can cause or aggravate respiratory conditions, allergies and other physical ailments. Mold and mildew can significantly damage the framework of your home, including roof trusses and framing. A moist attic area also creates a favorable environment for insects and vermin that could cause additional damage or simply be a nuisance.
  • Damage to stored items: Excess heat and moisture can cause damage to items stored in attics. Paper goods, such as books, important files, photographs, household records and cardboard boxes can be harmed by both heat and moisture. Electronics can also suffer serious damage from moisture and overheating. Family mementos or vital records can be destroyed, potentially valuable books or magazines can be rendered valueless, and once-functional devices could be made inoperable.
  • Unnecessarily high cooling bills: When large amounts of heat accumulate in the attic, it can radiate down into the living spaces below the attic floor. This causes the temperature inside your home to increase unnecessarily, which in turn will cause the air conditioner or heat pump to work harder to compensate for the additional heat. Cooling bills will be higher than necessary and living areas won't be as comfortable as you'd like.
  • Ice dams: Even in the winter, poorly ventilated attic spaces can cause issues that can lead to damage in the attic or elsewhere in your home. For example, if the space isn't ventilated properly, there's a greater chance that ice dams can form at the edges of the roof. Ice dams are accumulations of ice that form when snow and ice melt on the upper, warmer surfaces of the roof. As the meltwater flows down to the gutters, it hits a colder area at the edge of the roof, where it can refreeze and build up. When these ice dams form, they capture and hold water behind them, preventing the meltwater from draining away properly. The trapped water then has the opportunity to leak into the attic, down interior walls, or into other areas of your home where it can damage insulation, paneling, flooring, wall coverings or personal belongings.

Solutions for Attic Ventilation

In general, expert sources recommend one square foot of ventilation for every 3000 square feet of attic space. All of these options require that an opening be created in the roof and the ventilation system installed so that it can pull air out of the attic. Ventilation systems will also require a source of air intake for bringing in cooler outdoor air that will replace the hot indoor air. There are three main ways to achieve the necessary amount of attic ventilation for your home:

  1. Turbine vents: Turbine vents extend above the rooftop and are capped with a turbine that spins when the wind blows. The spinning action of this turbine provides the ventilation needed in the attic.
  2. Ridge vents: Ridge vents are considered among the most effective of non-mechanical ventilation options. They're installed at the highest peak of the roof and provide a series of ventilation openings that help move hot air out of the attic. To work properly, ridge vents require the installation of additional components called baffles, objects that keep outside air from crossing over the vent.
  3. Mechanical ventilation systems: Mechanical ventilation systems include devices such as attic fans and whole-house ventilators. These pieces of equipment provide a consistent level of air exchange for the attic space that prevents heat and moisture from building up. For the best performance, look for a fan that's powerful enough to replace the entire volume of air in the attic at least 10 times per hour.

Considerations for Attic Ventilation

There are several factors you should keep in mind when looking for solutions to attic ventilation problems:

  • Attic ventilation is appropriate in all seasons: Common sense indicates that any ventilation openings in the roof will let conditioned air escape in both summer and winter. While this is true to an extent, the minimal addition to your heating and cooling bills to replace lost air is an acceptable tradeoff for the benefits you'll get and problems you'll prevent from proper attic ventilation. For example, moisture is more likely to accumulate in a home that's buttoned up tightly against the winter cold. If necessary, increase the amount of insulation in the attic floor and interior ceilings to create an additional buffer against air loss.
  • Be sure to install enough vents: Even if there are vents in the attic already, there may not be enough of them to produce the amount of ventilation needed. Consult with your HVAC professional for help determining how much ventilation your attic space requires and how many of what type vents will provide it.
  • Don't overventilate: At the opposite end of the spectrum, it is possible to overventilate an attic space. Too many vents in the roof can lead to excessive loss of conditioned air and energy. Each roof penetration creates an additional area where water leaks or wind damage could occur. Again, rely on your HVAC expert to help you figure out how many vents are needed.

For more information on attic ventilation and its importance in keeping your home comfortable and avoiding roof damage, contact Griffith Energy Services, Inc. Our team of HVAC experts has been serving the home comfort needs of the Mid-Atlantic region for more than 100 years.

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