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Vented vs. Unvented Attics

It would make sense to want your home to be energy efficient and protected from the outside elements. Believe it or not, the attic and how it is ventilated and insulated is a very important piece of an energy efficient home.
Vented vs Unvented Attic

I have been hooked on home improvement shows since the early days of HGTV’s “Trading Spaces.” I love seeing the ways that a space or a home can become transformed. Most of these shows show you how things can be made more functional and beautiful. Sometimes the homeowners learn unfortunate news about foundation issues or the need to update the wiring.

I have yet to see an instance where the renovators talk with homeowners about the importance of ensuring they have a properly insulated attic. When trying to improve your home, it would make sense to want your home to be energy efficient and protected from the outside elements. Believe it or not, the attic and how it is ventilated and insulated is a very important place that can address these issues.

Vented vs. Unvented: What does it mean?

Vented Attic

For years homes have been built with attics connected directly to the outside. The only thing separating the inside and outside of the attic is a series of vents. This ventilation can be found in three main parts of the attic.

  • Soffit vents are found along the attic floor where the roof meets the wall.
  • The ridge vent is located at the peak of the roof line.
  • There may also be vents at the gabled ends of your attic known as gable vents.

Often, a thick layer of fiberglass or cellulose insulation will be on the attic floor. This layer of insulation protects the conditioned air in the main areas of your house from mixing with the attic air, which is just outside air being circulated via the vents. Air will come into the attic up through the soffit vents and go out of the attic via the ridge vent. Gable vents can act as intake or exhaust vents depending on the direction of the airflow. The purpose of attic vents is to help with moisture control in the attic, to keep attics from trapping too much heat in the summer, and to help with ice issues, like ice dams, in the winter.

Since this form of attic ventilation has been around for many years, you can know that it is relatively effective at doing its job. It is also less expensive to put in vents than to create an air seal and have an unvented attic. However, it is not perfect and has some shortcomings.

  • If your home is not airtight, you can be sure that your home will be leaking air. If you have air leaks, you can also be sure that the stack effect plays a role in losing your home’s conditioned air (heated or cooled). During the colder months, as hot air rises, the air pressure in the top part of your house gets higher and pushes out through your roof. The escaped air is replaced by cold air at the base of your home.

    The insulation on your attic floor can help slow this process, but without an air seal, it doesn’t stop. The stack effect is reversed in the warmer months. As air is cooled, it sinks and moves outward on the lower levels of your home, which causes warm air to be pulled in through the roof. As your home loses conditioned air, you are increasing energy usage and losing money.

  • Another issue that you run into with a vented attic is moisture. Even though one of the primary purposes of a vented attic is to avoid moisture build-up, a vented attic doesn’t prevent moisture from entering your attic. Moisture can enter the attic via the elements; think windy, rainy day. It will mostly be an issue when humid air enters, is cooled (even just a little) and creates condensation. Where there is moisture, there is a possibility for the presence of mold and moisture.
Unvented Attic

When an attic is unvented, there are no vents connecting the inside of your attic to the outdoors. The air in your attic will be circulated with the rest of your home through the HVAC system. If insulated properly, it can create an air seal. This will prevent air from escaping via the roof. It will also prevent unwanted moisture from getting in and causing problems.

An unvented attic also helps with pressure issues in your home and can make them safer. Here’s what buildingscience.com has to say about this, “Additionally, during high wind events, vented soffit collapse leads to building pressurization and window blowout and roof loss due to increased uplift. Unvented roofs – principally due to the robustness of their soffit construction – outperform vented roofs during hurricanes – they are safer.” The one drawback is that an unvented attic is more expensive upfront, but it will offer you savings and prevent problems in years to come.

If you are thinking about insulating your attic, we would love to help. Contact one of our foam specialists to see how we can assist you.

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