Proper ventilation is a practical necessity in every home, and a specific level or quality of ventilation is also a building code requirement. There are various types of vents to use, but one of the most commonly seen is the ridge vent. While it is helpful to know that ridge vents are a good and often-used option, they are not always the easiest option, so it is also important to know what the codes say about ridge vents specifically.
Ridge vents are not required by code. The International Residential Code does require homes to have ventilation, but there are many ventilation systems that meet these standards. Ridge vents are a very effective and economical option that also meets the IRC requirements.
All homes require ventilation, and ridge vents are an excellent option to use. Let’s more thoroughly examine the role of ridge vents in home ventilation systems, the effectiveness of ridge vents according to international building codes, and how these vents work to properly ventilate an attic or rafter space. We also look at alternatives if you are unable to install ridge vents.
The IRC Does Not Require Ridge Vents
Ridge vents are commonly seen on many homes, but they are not required by the International Residential Code (IRC). The IRC does state that ventilation is required, but not specifically ridge vents.
All states follow IRC regulations, but some states make their own adaptations based on factors like climate that can influence how ventilation needs to be achieved or maintained. Thus, your state’s local residential code may stipulate the use of ridge vents, specifically, so you should always check these regulations before finalizing your ventilation plans.
Do Roofs Need Ventilation?
All roofs are required to have some form of ventilation. All of the ventilation requirements for roofs are outlined in section R806 of the Internation Residential Code.
Ventilation is mainly needed to control air temperature within the home, particularly within the attic or roof of the building.
If a roof has no ventilation or it has inadequate ventilation, the air temperature in the attic may reach as high as 150 °F (65.5 °C) in the summer months. As you can imagine, this increases the home’s overall temperature, and it may cause severe damage to the roof itself.
You can keep track of the attic temperature by placing a wireless thermometer in the attic. You would be surprised how hot it gets there during hot summer days. I recommend Oregon Scientific sensors(Amazon). I have used them for years without problems. Battery life is excellent range is about 100 ft. which is more than enough for reading the attic temperature.
These high temperatures can structurally and functionally compromise the roofing shingles and materials, or lead to a build-up of condensation that can encourage the growth and propagation of molds and mildews within the roof.
Along with high temperatures in the summer, lack of roof ventilation leads to unstable air temperature in the attic during the winter. This may cause ice damming and other problems that can further damage the roof.
The most effective way to prevent these common, yet serious, problems is to ensure that the roof is adequately ventilated. However, there are some exceptions to the rule requiring a roof to be ventilated.
Exception
According to IRC section R806.5, there are numerous conditions that make a roof exempt from required ventilation. However, all of the criteria must be met in section R806.5 for the roof to legally exist without ventilation according to the IRC code.
Some of these criteria include:
- The unvented attic must be within the thermal envelope of the building.
- Interior Class I vapor retarders are not installed in the attic, on the attic floor, or on the ceiling assembly.
- The shingles of the roof are ¼ inches (6.4 mm) or more apart from one another and the roofing underlayment.
You can follow the link provided above for the full list of conditions that must be met for a roof to be exempt from the ventilation requirement. I have listed some of the most important criteria, but remember that every criterion in this IRC section must be met.
What Roof Ventilation Is Required by Code?
Now that we know ridge vents are not required by the IRC, and we know that some roofs are even exempt from the ventilation requirement entirely, let’s look at what the IRC does stipulate regarding ventilation because this will apply to the majority of homes.
Section R806.1 of the International Residential code states that enclosed attics and rafter spaces that have a ceiling attached directly to the underside of the rafters must have cross ventilation for each space, this means there should be openings on either side.
Furthermore, the vents must be protected so as to not allow rain or snow to enter through them. After all, ventilation shouldn’t compromise weatherproofing because this would lead to a whole new set of issues!
The ventilation openings must meet the following criteria:
- They must have a minimum opening of 1/16” (16 mm).
- They must not exceed 1/4″ (6.4 mm).
- Any ventilation opening that has a diameter larger than 1/4“ (6.4 mm) must be covered with a corrosion-resistant screen with an opening diameter between 1/16″ (16 mm) and 1/4″ (6.4 mm).
- All vents must open directly outside.
- All vents must be protected from birds, rodents, snakes, and other small animals.
Related Article: How to Stop Wasps Coming Through Vents
Code-Mandated Minimum Ventilation Areas
All ventilated roofs must adhere to the IRC regulations that state the minimum ventilation areas of a roof.
The IRC refers to the net free ventilation area, which describes the amount of space available in the vents that can be used to freely pass air—i.e., it refers to the gaps in the vents.
The IRC regulations state that the net free ventilating area of the attic or rafter is required to be at least 1/150 of the area of the vented space.
This means that the size of the vents in the roof must have a minimum combined open area of 1/150th of the total area of the attic or rafter space. For example, for 150 square ft of rafter space or attic space, there must be at least 1 square foot of ventilation.
Exception
There are two criteria that exempt ventilation systems from the 1/150th net free ventilation area rule.
Both criteria must be met for the house to qualify as exempt, but if it does, then it is only required to have a net free ventilating area of at least 1/300th of the vented space. This means that for every 300 square ft of space, 1 square foot of ventilation is required. Thus, houses that meet the exception categories require smaller ventilation areas than houses that do not.
The first exemption criteria is if Class I or Class II vapor retarders are installed on the warm-in-winter side of the ceiling in houses in climate zones 6, 7, and 8, which are the coldest regions in a country.
The second is if 40-50% of the net free ventilating area is provided by ventilators located in the upper portion of the space. However, this criterion only applies if the upper ventilators are located less than 3 ft (914 mm) below the highest point of the space. The remaining required ventilation must then be located in the bottom third of the attic space.
Ridge vents are an excellent way to achieve a 40-50% net free ventilating area located less than 3 below the highest point in the roof.
How Do Ridge Vents Help Provide Sufficient Ventilation?
Ridge vents are surprisingly effective ventilation systems. These vents encourage the natural flow of air from the attic or rafter space and promote air circulation within the home by merit of their location.
These vents work by allowing hot air to rise (as it naturally does) and exit through the vent, pulling cool air along with it. This generates an airflow that continuously removes hot air from the attic. The effect acts similarly to a vacuum and actively pulls air through the vent, but without the need for a motor of some kind.
On windy days, the wind from outside the house will pull air from the vent even more rapidly, increasing the effectiveness of the ridge vent.
Ridge vents help provide sufficient ventilation to the roof by promoting a continuous airflow out of the attic or rafter space of the house and constantly pulling fresh air in from below. This makes ridge vents very effective yet straightforward ventilation systems.
Additionally, as they pull air through the whole house (when given a clear passage to do so), they can be used as a method for ventilating rooms without a window.
Related article: Ridge Vent Pros and Cons
Ridge vents are also a great option if you are looking for subtle but effective passive ventilation for your shed.
Ridge Vent Alternatives
Ridge vents are only one type of upper exhaust ventilation that is available for use in homes. Ridge vents are very effective, but they are best used in homes with shingled roofs and homes with attics or rafter spaces.
This means that ridge vents are not always the best option, but there are some alternative vents that can be used.
Some ridge vent alternatives include:
- Box Vents – these vents are installed in the roofs of homes that have an attic or a rafter space. They remove hot air and moisture from the house by convection and natural air currents.
- Soffit Vents – these vents allow air to flow into the house as they are installed under the overhang portion of the roof. There are various types of soffit vents that can be installed based on the type of roof and ventilation needs of a particular home.
- Turbine Vents – these are the rotating vents that are very commonly seen on many types of homes. Lights winds rotate the turbine, which then pulls air out of the home through the roof.
- Eyebrow Vents / Turtle Vents – these vents are usually installed in pairs to maximize airflow. They are usually curved open vents on sloping sections of roofs and are very effective.
Ridge Vent Pros and Cons
| Ridge Vent Pros | Ridge Vent Cons |
| Roof ventilation is required by code and ridge vents are a good method for achieving this | There may be a risk of leaking from ridge vents with heavy rains |
| A great way to keep your attic cool and for dealing with humidity | Ridge vents are only appropriate for sloped and not flat roofs |
| Small enough to be installed along the entire roofline for maximum ventilation | Lower vents are necessary to properly ventilate with ridge vents |
| Improve the ventilation and cooling system for your whole house | Improper installation makes them ineffective |
| Inconspicuous ventilation system that blends with your roofing system | Ridge vents rely entirely on passive airflow |
| Small enough that you won’t have to deal with animals getting in | |
| No vent stacks or hood are needed |
Pros of Ridge Vents
Roof Ventilation is Required by Code
Section R806 of the International Residential Code (IRC) requires roof ventilation:
“Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow.”
These openings must be between 1/16” and 1/4” in dimension (bigger than that requires a screen).
While ridge vents are not required by code, they are a good way to achieve roof ventilation, which is required by code.
It is important to check your local code on ventilation before you install ridge vents (or any ventilation system) to ensure that you comply with regulations that may be different from those in the IRC.
Ridge vents make use of the natural airflow in a house. They are designed to allow hot air to filter to the outdoors as it rises. This results in a vacuum-like ventilation system, creating movement in the air by pulling cooler air along with warm air in a continuous upward flow.
Keep Your Attic Cool
As the highest point, your attic is likely to be the hottest area in the house, even in the presence of an air conditioning system. This is because hot or warm air rises and because sunlight beats down onto it.
The potential for holding heat is part of the reason you need to ventilate your roof (aside from airflow); heat can cause structural damage.
If you install ridge vents that utilize the natural airflow of your house, you are going to be providing a way for that hot air to escape the attic and be replaced by cooler air.
Not only do ridge vents help with hot air in attics, but they also allow humidity to escape through them. This will help to keep your attic mold and mildew free and therefore should demote it from your worst nightmare in terms of cleaning and potential health threats.
Overall, your attic should be less homey for any interested animals and you are going to find that it suddenly has a lot more functionality without the risk of ruining anything you put up there.
Now, if you consider the regular heat and humidity issues associated with an attic, imagine how these issues would be compounded if your bathroom fan was improperly vented and terminated in your attic! If you can’t quite imagine it, I have put together a vivid list of the Reasons Why A Bathroom Fan Should Not Be Vented Into the Attic.
Even Venting Along Entire Roofline
Ridge vents are placed at the tip of your roof peak and are simple enough to install along the full length of your roofline. This makes it easy to achieve good ventilation for your house in a way that complies with building code requirements.
Using ridge vents is also a good way to ventilation multiple sections within the attic or rafter space, without trouble, even if those sections are divided by walls. You don’t need to stress about how you will get sufficient airflow through all the individual spaces.
Air circulation is also more even and efficient when you use ridge vents as there will be more access to openings in the vent system for air to move around.
Ridge vents look more uniform (which will please the asymmetry-disliking members of your family!) and just adds to the overall cohesion of your house design.
Placement of your vents will not be an issue as you will not have to consider vent placement based on any trees or chimneys that might block airflow around a vent stack or hood.
Improves Whole House Ventilation and Cooling
The ventilation and cooling benefits of ridge vents are not limited to the attic. The system works in the same way for the entire house.
Ridge vents help to balance out the temperature of your house by moving air around and in and out. It helps to keep your whole house cooler in the warmer months.
Don’t worry though, this doesn’t mean that your house will be freezing during the winter!
By design, ridge vents help to trap the warmer air in your house when the air is freezing outside. Which helps to keep your house warm and should help keep your heating bills down.
Inconspicuous
Ridge vents are designed to be inconspicuous and to blend into your roof in comparison to the bulky turbine and stack vents.
They sit at the peak of a sloped roof and can be color-matched to the roof as they are covered with your roofing tiles.
They are small and unobtrusive while providing maximum ventilation for your house. So, ridge vents won’t interfere with your décor and stylistic endeavors.
Personally, I prefer the ridge vent style as they don’t make your roof look like it belongs on a factory the way that protruding vents do.
Small Enough to Prevent Animals Entering
No one wants to deal with raccoons, rats, mice, birds, and a variety of other animals in their attic and rafter space. They can cause a lot of trouble and it’s not always easy to get rid of them.
Thankfully, ridge vents are comprised of slim openings that prevent any freeloaders from getting in. Saving you from costs related to chewed wires, damaged ducts and insulation, the “thrifting” of nesting materials, and a whole lot of poop.
There are also health risks to having animals living in your roof or attic:
- Chewed wires are a fire hazard and lead to further damage to your electrical system. And let’s face it, the wires that are found in the roof are generally the kind that connect to large and important appliances and the lighting circuit.
- Ducts serve a purpose such as directing plumbing line gases and exhausted air out of the house. If these are damaged, then they might start pumping those things back into the house.
- Animal feces and urine in your roof are not hygienic. This is a great way for you to pick up germs and parasites. You also risk having your ventilation system circulating the particles throughout your house. No one wants to be exposing themselves or their families to that!
With ridge vents, you won’t have to worry about these factors or about animals creating blockages in your ventilation system. Although it is still worth checking and cleaning these vent openings annually.
Additionally, and most importantly I think, you circumvent the scurrying sounds that no one wants to hear on scary movie night.
No Vent Stacks or Hoods Needed
When it comes to vent stacks and hoods, there is a higher chance of leaking. Even with the flashing that is installed with this type of equipment, there is still a pretty large opening in your roof that should not really be there.
Ridge vents fit more seamlessly into the shape of your roof and so do not share the same problem as vent stacks and hoods.
Ridge vents are also less exposed to the elements due to the more integrated installation and so suffer less weathering. This means you are not going to have to replace or repair them as often and less damage to the vents means less risk of damage to your house.
As mentioned, another bonus is that ridge vents have a lot less impact on your roof aesthetic than these alternatives.
Cons of Ridge Vents
Risk of Water Leaking Inside From Heavy Rains
According to the IRC Section 806, the ventilation openings must be installed in such a way so as to protect them from rain.
Weather protection for ventilation systems in roofs is defined in IRC Section 903.1, which says that your roof system must be installed according to the IRC (or to the adaptations in your local code) and the instructions of manufacturers in a way that protects your structure.
Your roof has a roof assembly. This is a system that is specifically designed to protect your house from weather conditions all year around.
This means that if you have installed the ridge vents according to the manufacturer’s instructions and so as to meet building and residential code requirements in your area, then there should not be issues with leaking because of ridge vents.
However, if you stay somewhere that commonly experiences bad weather conditions and storms you may need to keep an eye on your attic and rafter spaces for water damage as strong winds may be able to blow water inside.
Not Appropriate for Flat Roofs
Ridge vents are made to be installed at the apex of sloped roofs. The placement of the vent opening and the mechanics of how they are designed to move air means that ridge vents are not appropriate if you have a flat roof.
This is because ridge vents require a level of elevation and an angle that cannot be achieved on flat or flatter roofs.
If your roof is flat, you will need to consider other ventilation systems that are suitable for your structural needs as ventilation is still important. It will still be required by code and can still cause structural damage the way it does with sloped roofs.
Box vents and soffit vents may be viable alternatives, but it depends on your local coding and the structural design of your house.
If you are unsure of anything when it comes to ventilation, it is always best to contact a professional.
Works Best in Conjunction With Lower Vents
Ridge vents work with natural airflow and lack an exhaust or fan component to mechanically create air movement. While this is a great ventilation method, there is a problem in terms of structural design.
Older houses aren’t necessarily designed with the same energy-efficient structure that you tend to find in newer buildings. This means that you might need lower vents in order to achieve optimal ventilation.
Lower vents, such as soffit vents, are put in at lower points on the house. Soffit vents are installed under the overhang of your roof which allows air to enter the house and helps to create a more effective ventilation system.
While I say that ridge vents can be used in conjunction with lower vents to improve ventilation, this does not mean that they are ineffective on their own if the house is suitably designed.
I want to note here that the building codes also specify that if you have vents in the upper section of your attic, you also need some in the lower portions. You can read more in my article on ridge vents and their fulfillment of code ventilation requirements.
Improper Instalment Can Make Them Ineffective
The effectiveness of ridge vents depends entirely on whether or not they are installed properly.
- If ridge vents are installed on a roof shape that is not appropriate, then they will not provide effective ventilation.
- Improper installation will also compromise the weather resistance of your roof system, which means you will have problems with rain and snow and this will impact the temperature balancing capabilities of the ventilation system.
- Any blockages in the vents will prevent airflow and will decrease the ventilation quality in your house.
Due to the importance of ventilation for roofs and the coding requirements for this, it is advisable to seek professional help and installment to ensure that ridge vents are the best option for the house and are installed properly.
Rely Entirely on Passive Airflow
Ridge vents rely entirely on passive airflow to provide ventilation for your roof and house. Unlike turbine or mushroom vents that also have a degree of mechanical venting because air currents drive the fan, which can help pull air up through the vents more effectively.
Vents that rely on passive airflow use the chimney effect, using air buoyancy. Without the use of a fan, exhaust, or motor that active airflow vents use to circulate and move air and moisture the passive air vents are a lot slower.
Active airflow is more continuous in comparison to passive, although ridge vents are considered to give continuous airflow in ventilation.
But when it comes to passive airflow, factors such as the temperature of your attic and the air outside, the moisture levels in the air, the height and angle of your roof, and wind velocity can impact how effective your ventilation is that day.
When it comes to deciding which option is better for your home you might need to consult a professional.
Sources
https://www.greenbuildingadvisor.com/article/all-about-climate-zones
https://www.energy.gov/eere/buildings/climate-zones
https://benjaminobdyke.com/insights/how-does-ridge-vent-work/
https://www.improvenet.com/a/roof-box-vents-vs-continuous-ridge-vents
https://greengarageblog.org/12-roof-ridge-vent-pros-and-cons