The Ins and Outs of Roof Exhaust Vents

Winter rains have arrived and the summer’s warm, dry air has been soundly replaced by cold moisture. This can prevent a problem in your home if your roof isn’t properly ventilated. When you turn on the heat in your house in the winter that now warmed, moist air accumulates at the highest point in your home, and without an escape route through a roof exhaust vent or attic exhaust fan, that trapped air encourages mold and mildew growth and creates a stale odor. 

To avoid these problems, it pays to ensure your roof exhaust vent is properly installed and maintained. 

Types of Roof Exhaust Vents

There are different types of roof exhaust vents:

  • A box vent is a hole that is cut through the roof that has a box cover over the opening. Box vents are positioned near the roof peak for maximum exhaust ventilation. 
  • The ridge vent is a continuous strip of plastic material covering a strip of removed roof deck about one inch on both sides that allows continuous airflow due to convection. There must be an equal intake to output ratio in order for air to convect upwards and out of the building. 
  • A stem vent is used to connect your bathroom, kitchen, or dryer fans to allow the moisture to escape properly and reduce moisture in the attic and in your home

All of these roof exhaust vents are non-powered or passive, working in tandem with soffit vents that sit at the lowest point of the roof to draw in outside air. The two types of vents together circulate the air keeping the heat and moisture to a minimum and your attic properly ventilated.

Power Fan Exhaust

In addition to roof exhaust vents, there are also attic exhaust fans. They work under the principle that hot air rises, but here instead of the hot air simply escaping through vents, it triggers an electric-powered fan to switch on to push the hot air outside. This creates a powerful suction drawing up the warm air and blowing it out through the roof. Removing heat in the attic stops the heat from radiating down into the house which then keeps the air conditioning unit from turning on, making it more efficient. While a very efficient solution for keeping a house comfortable, the fans are installed below the roof and can be quite heavy, so they cannot be installed on every type of roof. 

Attic roof vents are similar to bathroom and kitchen roof vents in that they all suck “bad” air up and out of the house. However, bathroom and kitchen exhaust vents are smaller and powered by exhaust fans that you turn on when needed. Kitchen and bathroom vents can also be directed to release air through the home’s siding, not just the roof. Those metal protrusions you see on the sides or tops of houses are usually exhaust vents that have a type of protective covering to keep moisture and pests from getting inside.

Inspecting Roof Exhaust Vents

Having roof vents is a critical part of keeping your roof in good shape and your home comfortable, but having them is just part of the solution. Regular inspections and maintenance of roof exhaust vents, and ensuring they were installed correctly, are also part of the effort. 

Contrary to popular belief, warm weather doesn’t produce moisture on nail heads, but cool weather outside and warm attics will. This is because the cold transfers through the steel nail, putting a cold rod into a warmer attic, creating a dew point where the warmer air carrying moisture meets the cold steel and condensation begins. This is the same as when you put a glass of ice water on the counter and it collects dew on the outside of the glass. The moisture in the room gravitates to the colder surface. This is exactly the same process on the nail in the attic.

The best way to ensure proper roof exhaust venting is to hire a professional roof contractor to conduct an inspection. Pacific West Roofing offers roof exhaust vent service starting with having our expert inspectors assess your roof, attic, and vents for signs of damage or blockage. Then repairs and replacements can be made to ensure your roof is sound and sufficiently ventilated. Hiring the best and most experienced  professionals to install your roof exhaust vents in the first place can go a long way in keeping your roof, your home, and the very air you breathe inside your home in tip-top shape. Contact Pacific West Roofing to find out how we can serve your roofing needs. 


The Importance of Attic Ventilation

If you’ve ever spent any time in your attic—even just to poke your head in to take a quick look—you have no doubt noticed the difference in temperature from the rest of your home. Depending on the time of year, your attic space will be either warmer or cooler, which is just as it should be. The air in your attic should also feel dry, and with properly balanced attic ventilation, it will be.

Why Balanced Attic Ventilation Matters

The ventilation system in your attic is meant to regulate the temperature and the humidity level (moisture) in your attic. And while temperatures may vary through the season, properly balanced ventilation will ensure both optimal temperature and humidity levels and will prevent condensation and mold.

The benefits of properly balanced attic ventilation:

  • Prevents excessive heat in your attic, which can lead to the plywood in your roof deck (the attic ceiling) delaminating and causing your roof shingles to degrade faster. An attic that is too warm in the winter may also cause faster snow melt and ice dams that can lead to leaks or gutter damage. 
  • Prevents excessive humidity and moisture that will create the perfect environment in your attic for mold, mildew, and rot, which can damage a roof and shorten its life span.
  • Keeps energy costs down by regulating the temperature in your attic. The constant flow provided by the intake and exhaust vents prevents your attic from ever becoming too hot. In the heat of summer, this means your air conditioner is not going to work as hard to keep your house cool.
  • Prevents thermal cycling, the hot and cold contractions that weaken roof material—shingles, sheeting, plywood—and cause them to degrade more quickly.

Attic Intake and Exhaust Vents

Proper attic ventilation includes both intake and exhaust vents, which work in concert to pull air into, through, and back out again, providing continual airflow. Intake vents should be located at the lowest point in your attic to allow cooler outside air to flow in. Conversely, exhaust vents should be positioned at the highest points so rising hot air and damp air can escape.

Depending on the size and configuration of your attic and roof, different types of attic vents are necessary. 

Intake Vents

  • Soffit Venting. The soffit is the part of your roof overhang that meets your siding and is the lowest point in your attic. Soffit vents come in two types—rectangular and continuous—and are intake vents that work to draw cooler fresh outside air into your attic.

  • Rectangular soffit vents are holes that have been cut into the blocking between the rafters of your roof. The holes are covered with a screen or vent cover, which allows air to flow through but prevents birds and insects from entering your attic, depending on the size of the vent or screen openings.
  • Continuous soffit vents run along the full length of your home’s closed soffit and incorporate a perforated material or wire screen that allows continual airflow into your attic at the lowest point. This type of venting can only be installed in closed soffits where the roof rafters are not visible.
  • Gable vents, which may be positioned on the exterior wall of an attic, allow air to flow in or out but generally do not help even airflow throughout the attic. 

Exhaust Vents

  • Roof Venting allows rising hot air and moisture to escape from your attic, preventing heat build-up and condensation, depending on the season. There are two primary types of residential roof vents: Box Vents and Ridge Vents.
  • Ridge vents are attic exhaust vents installed along the peak of your roof. As they are positioned at the highest point, ridge vents are extremely efficient at allowing hot or damp air to escape. Continuous ridge vents also help create a bit of a vacuum that enables the desired air circulation. This type of attic exhaust venting is visually appealing as it blends well into the roofline.
  • Box vents are another common attic exhaust vent positioned near the top of the roof to provide an outlet for warm air. These vents are comprised of a hole that has been cut into the roof and essentially a  box cover over the opening.

  • Turbine vents, although not as common on residential roofs, are another type of passive (non-powered) exhaust vent. Rising heat in the attic causes the turbine vents to rotate, creating a drawing effect that pulls air through the attic.

Attic Fans

A properly installed attic ventilation system with the optimum number of intake and exhaust vents results in a highly efficient passive system that does not require any electricity or power to run. Most homes are constructed with passive attic venting comprised of intake and exhaust vents.

Attic ventilation fans are sometimes installed to aid in air circulation and may help the energy efficiency of a home’s HVAC system. Attic fans are typically installed on the attic ceiling (to help circulate and draw warm air up) or gable (to help draw cooler air in or push warm air out). 

Attic Thermostats and Humidistats

Power attic fans will often have a dual thermostat and humidistat to measure the temperature and the humidity in the attic and automatically adjust the fan to maintain optimal levels. This automatic control can help improve the performance of the home’s heating and air conditioning system as well as mitigate condensation and delamination of plywood.

Attic Ventilation Installation and Maintenance

While the best time to install an attic ventilation system is at the time of a new roof installation or roof replacement, ventilation can be modified with additional venting later on if necessary. Old or damaged roof vents should be repaired or replaced to prevent leaks or other damage to the roof.

You can do a quick visual assessment simply by walking around the exterior of your home to determine the number and type of vents your home has, but this will not tell you if the ventilation is balanced or working as it should. Touching the ceiling of any room immediately below your attic can help determine if the attic is too hot (the ceiling should not feel warm).  You can also do a visual check for moisture and signs of mold or rot in your attic. But the best way to know if your attic is properly vented and that all vents are in good condition is to have your roof and attic inspected by a professional roofing contractor. 

The roofing and ventilation technicians at Pacific West Roofing are experienced with residential ventilation and what compromises a properly balanced system for optimal airflow. We can also identify damaged vents or even broken seals where new caulking is needed—the little details that are often overlooked can lead to costly repairs.

If it has been a while since you’ve inspected your attic, roof, or vents, don’t wait for another season to pass and risk developing leaks or other problems. Contact us today to schedule an inspection. We’ll give you an honest assessment and top recommendation to maintain the health of your roof, attic, and home.


Don’t Get Stuck in an Attic Vent Trap | Pacific West Roofing

attic insulation and ventilationAttics are both very useful and inconvenient at the same time. If you wonder how this could be, consider the pros and cons. Attics can provide indispensable storage space, but the things that can be stored in an attic are often limited to boxes and other small items that are light enough to be hoisted overhead. Another negative– yet entirely avoidable– characteristic of attics is extreme heat in the summer and trapped moisture in the winter. Proper ventilation can alleviate both of these environmental issues, but you need to make sure that your vents are installed properly and working together seamlessly for the best results.


Attic vents can prevent a handful of costly home repairs, but not if they are used improperly. It is extremely important to have these vents installed correctly, otherwise they can do more harm than good. There are several common mistakes people make when dealing with vents, but you can avoid them by keeping clear of these four problems:

  1. Unbalanced intake and exhaust installation – There are two types of vents that keep your attic cool and moisture free, they are intake and exhaust. By building a system that is overbalanced with one type of vent or the other, the ventilation system will not function properly.
  2. Concentrating only on summer heat – If you’ve climbed up into your unventilated attic during the summer, odds are high that you began sweating almost instantly. However, temperatures soaring well over 120 degrees are not the only attic issue you should worry about. The winter months can cause moisture buildup which can be damaging. Attic vents are designed to work all year long and should not be neglected during cooler times.
  3. Mixing and matching ventilation strategies – Attic vents are successful because of a delicate balance that keeps air flowing in and out, while also protecting the attic from outside weather. There are a few different combinations of vents you can use to draw air in and let it escape, but they are not interchangeable. For example, installing two or more different kinds of exhaust vents can sometimes cause the system to fail and allow wind and rain to enter into the attic.
  4. Not sealing off attic bypasses – In order for an attic ventilation system to work, the attic must be a contained air system, which means that openings like leaks or cracks that are not intended let in outside air should be sealed or repaired.


To guarantee that your attic is properly ventilated, call a professional roofer to have your vent system repaired or installed correctly. With the help of an experienced contractor, your attic will become much more efficient at dispelling hot or moist air, effectively lowering your energy bill and preventing water vapor from damaging your home.

Contact Pacific West Roofing about attic ventilation today. Call 503-635-8706 or click here to request an estimate!



Attic Ventilation: Critical to a healthy home | Pacific West Roofing

Houses built back in the day, could breathe both through the window frames, light fixtures, switch plates and not-so-tight siding with building paper that was very porous. Today is a totally different story. The building “wrap” installed under siding today is very tight and permeability is almost non-existent. Moisture that used to exit through the building now travels through the inside of the building, rising with heat and winding up in the attic.If not vented properly, this moist air in the attic will condensate at the lowest points of the roof deck during the colder months of the year.

Now here comes the true purpose for a balanced ventilation system in your attic. Once this moisture rises into the open attic, there needs to be adequate exhaust ventilation at the ridge as well as adequate intake ventilation at the soffit or bird blocks. Bird blocks are the blocks between the rafters where they rest on the plate of the exterior wall of the building. These bird blocks are usually 2×4’s of wood which space the rafters 2 feet apart. These blocks are either blank or have holes with screen covering the holes to keep birds and bugs out but allow air to flow in as heat rises out of the exhaust vents or ridge vent.  The formula is 18 inches of net free air (NFA) per running foot of ridge to exit at the ridge vent, or can vents, and 9 inches of NFA of intake air per side of the house times 2 sides equals 18 inches of intake air to match the 18 inches at the ridge exhaust. This is a balanced system.

The vented wood bird blocks are grossly undersized for intake and most have maybe 10 inches of NFA in the 2 foot block it sits in making it 8 inches short of the needed 18 inches of NFA needed in the 2 foot span it uses. There is a cure for the undersized bird blocks and that is to replace the bird block with a full screen replacement vent which is a corner-to-corner screen giving the vent a 48 inch NFA for that 2 foot span of a 2×4 bird block. That translates to 24 inches per running foot well over the 9 inches per foot needed for adequate intake vent. Now….how often should you space these intake vents? I say no more than two blanks between vents or you will end up with dead air pockets and then the condensation begins again. I recommend every other rafter bay to make the air move some of the air in the “dead” or blank rafter bay. Yes, it can be considered overkill and I love to be over than short of intake, which is exactly what Air Vent Inc. suggests we are to do. Visit for information on what I have discussed here.

Now that we have addressed the exhausting of heat and moisture in the attic, we need to look for moisture contributors in the same space. Bathroom exhaust fans are usually the culprit for shoving moisture into poorly vented attics causing the mold that eventually decays the roof deck to the point of needing total replacement. These vents are easy to fix by installing a baffled 4 inch vent with a goose neck or nipple sticking down off the bottom of the vent to slide the typical 4 inch ducting from the fan directly over the nipple then taping them together well with HVAC foil tape to stop air leaks…air now exits the building and not into the attic. This is step 1 in stopping the attic moisture source.  Step 2 is the kitchen vent where you will repeat step 1, taking the steam from your stove and putting it directly outside, not into the attic. With this solution, the only vaporized moisture that will get into the attic will be the moisture produced from inside the house from normal heating and living, which will easily be evacuated by the intake and exhaust vents we prescribed earlier in the article.

A happy attic is a moisture free, dry attic!

Portland Roofing Contractor Since 1980

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