If you’re wondering “how do I know if my home is ventilated?” Let Republic Roofing help you out. We can construct a beautiful roof with quality shingles, neat detailing, and straight, clean lines that match your home’s color. It’s just as important to pay attention to what’s happening underneath your roof, in your attic space.
A roof’s lifespan can be affected by air movement and temperature, and your heating and cooling bills can be dramatically affected as well. Let’s examine the unique features and challenges that come with having an attic space.
What is the attic?
Every home has an area for ventilation under its roof decking. This area may not have a walkable space, but every home has some type of ventilated space.
How does my attic temperature affect my home?
Throughout your home, hot air rises, creating a stuffy, stifling pocket of air underneath your roof. The signs of this trapped warm air vary, but perhaps you noticed it last time you went searching for those old baseball cards in your attic.
How to do roof and attic ventilation work?
Airflow in the attic
There are two types of vents in the attic that allow air to flow: intake vents and exhaust vents. In addition to pulling in the fresh air, this constant air exchange vents stale air, keeping your attic space cool.
There are two principles to remember when dealing with attic ventilation.
- Warm air rises
The warm air from the dwelling below the attic rises into the attic space as the dwelling below cools. In cases of inadequate ventilation, this can result in dangerously high attic temperatures due to the heat from the sun (conductive heat from the roof). It is not uncommon for temperatures in an attic to reach 130 degrees Fahrenheit during the summer months.
- Warm air absorbs more moisture than cold air.
In cooler months, warm air rises from the dwelling into the attic space. The moist warm air carries a significant amount of moisture from the dwelling. In the attic, as the warm air cools, condensation occurs. Without proper ventilation, this condensation can cause serious damage to the roof structure, leading to costly repairs in the long run.
Intake Vents vs. Exhaust Vents
Your attic is ventilated by intake vents at the eaves or at the lower part of your roof. The vents allow fresh air to enter the attic. Intake vents are most commonly part of soffits. Cooler air enters the attic through these vents since they are located below the exhaust vents.
At the end of the attic or at the peak, the exhaust vent directs the hot, moist air outside after being circulated through the attic.
How much ventilation does an attic need?
Official attic ventilation recommendations still exist. As a rule of thumb, there should be a minimum of 1 square foot of venting per 300 square feet of attic space (evenly split between intake and exhaust). Using GAF’s attic ventilation calculator, you can determine the amount of ventilation you need for your attic.
What are the different types of attic ventilation?
Six main types of attic exhausts
- Ridge Vents
Ridge vents are the best exhaust vents for steep roof applications where the attic is open and the soffits are adequately ventilated. Despite the availability of many types of ridge vents, many need to be more robust or even counter-productive. An enough designed ridge vent will allow air to circulate evenly throughout your attic, unlike a fan or louver, which exhausts air only where it’s installed, leaving pockets of uncirculated air.
- Power Fans (solar or electric)
Many houses with hip-style roofs have short ridge lengths, so power fans are helpful in areas where ridge vents are not available. Power fans should have a humidistat included if they are needed to reduce humidity in the attic. A humidistat will operate the fan if it detects a high humidity level in the attic. This can help protect the interior of your home while also saving you from potential health hazards.
- Wind Turbines (aka Whirlybird Ventilation)
For optimal attic ventilation, however, other forms of ventilation are much more effective than wind turbines or roof louvers.
- Gable Louvers
Additionally, gable louvers don’t provide any real airflow, as they are only capable of passively allowing air to enter the attic rather than actively pushing the air out. This means that the warm, moist air that accumulates in the uppermost areas of the attic will not be vented away and can lead to condensation, mold, and other damage to the roof.
- Roof Louvers (aka Box Vents)
- Cupola Vents
Four types of intake systems
- Soffit Vents
- Gable Vents
- Over Fascia Vents
- Drip Edge Vents
What type of attic ventilation is best?
The best-case scenario is to install ridge vents and soffit vents. The type of roof on your home can have a prominent effect on the type of attic exhaust that would work best for you. The use of other ventilation systems is recommended if your home is not complete with a long enough ridge, such as a hipped roof.
An attic fan is the best form of ventilation if your roof is flat or low-sloped and you have an attic below it. Wall louvers or pop vents can remedy problems with air intake.
There is a common misconception that attic fans vent an entire roof instead of a section of the attic. As a result, some sections of the attic may still have heat and moisture, causing problems with heating and cooling and mold if the problem is severe. In addition, electric attic fans can fail due to mechanical failures, whereas ridge vents are able to remove heat and moisture from enclosed attics without requiring electricity.
Attic ventilation systems to avoid
If the ridge length is sufficient, a ridge vent should be installed. Mixing different types of the attic exhaust is never a good idea. The installation of a roof fan and a ridge vent is often done by contractors who are unaware of ventilation practices.
This is because the fan is creating a negative pressure in the attic, which pulls air in through any available openings, such as the ridge vent. The fan then exhausts this air, creating a cycle of air being drawn in and exhausted. The ridge vent is not designed to be airtight, and when it’s not sealed properly, air from outside can get in. This can lead to airflow issues that can cause moisture buildup, mold, and mildew, as well as other topics.
Is Attic Ventilation Required?
Attic ventilation has been required in all building codes since 1948. The IRC’s requirements are revamped every three years, so the 2018 edition is the most updated. Despite this, attic ventilation regulations have remained relatively unchanged. Here are some highlights from Chapter 8, Roof-Ceiling Construction, Section 806, Roof Ventilation.
The following is taken from the IRC:
R806.1 ventilation is required.
For enclosed attics and enclosed rafter spaces, ventilating openings protected against the entry of rain or snow should be installed in each compartment by applying ceilings directly to the underside of roof rafters. The minimum dimension of ventilation openings shall be 1/16 inch (1.6 mm), and the maximum dimension shall be 1/4 inch (6.4 mm).
With a minimum extent of 1/16 inch (1.6 mm) and a maximum dimension of 1/4 inch (6.4 mm), ventilation openings with a minimum dimension of 1/16 inch (1.6 mm) and a maximum dimension of 1/4 inch (6.4 mm) must be covered with corrosion-resistant wire cloth screening, hardware cloth, or perforated vinyl. The roof framing members shall have openings that comply with Section R802.7. Openings for ventilation shall be able to be opened directly to the outside air and must be sealed off to prevent birds, rodents, snakes, or other creatures from entering.
R806.2 Minimum vent area
The minimum net-free ventilating area shall be 1/150 of the vented space area.
Exception: In the event that both of the following conditions are met, the minimum net free ventilation area should be 1/300 of the vented space:
- The warm side of the ceiling is installed with a Class I or II vapor retarder in Climate Zones 6, 7, and 8.
- The upper portion of the attic or rafter space should provide at least 40% and not more than 50% of the required ventilation area. There should not be more than 3 feet (914 mm) between the top of the upper ventilators and the top of the space, measured vertically. Attic ventilation shall be provided for the remainder of the space in the bottom one-third. Upper ventilators shall not be installed more than 3 feet (914 mm) below the ridge or highest point of the space if the location of wall framing or roof framing interferes with their installation.
The article only discusses the 2018 IRC, as previously mentioned. This is especially important since codes are constantly changing, and municipalities may have adopted amendments that are specific to their area. It is essential to understand the building code in the specific location in order to ensure compliance.
Attic ventilation affects your roof warranty and integrity.
All roofing shingles manufacturers stipulate attic ventilation. The attic ventilation helps keep the attic cool and dry, which will help extend the life of the shingles. Without it, the shingles may become damaged from prolonged exposure to heat and moisture, which could cause them to warp and become brittle. This is why it is important for roofers to install adequate attic ventilation when installing a new roof.
Results of Improper Attic Ventilation
Effects of heat buildup in the attic
Hot air rises, so the heat in the attic space rises as well, creating a convection current that transports the heat from the lower floors to the attic. Additionally, the insulation in the attic helps trap the heat and keeps it from escaping, further exacerbating the problem.
Heat rises and gets trapped in the attic, causing the air temperature to be much higher than the air temperature in the rest of the house. This heated air then works like a blanket, heating up the rooms below. The heat buildup in the attic also damages the roofing materials, causing them to weaken and become less effective at protecting the house.
Effects of Moisture in the Attic
In cool months, moisture can cause trouble. As a result of everyday household activities, such as cooking, showering, and breathing, humidity rises. This moist air then enters the cool attic space. As soon as it hits the cold underside of the roof, it releases moisture in the form of condensation. The condensation can also lead to structural damage to the roof, as the water can seep into the wood and cause it to rot and weaken. It can also create an environment that is conducive to the growth of mold, which can cause respiratory issues. Additionally, condensation can reduce the effectiveness of the attic insulation, leading to higher heating costs.
How proper attic ventilation works to keep your home healthy
An attic with proper ventilation helps to keep the temperature and humidity levels in the attic balanced with the outside environment. This helps to prevent moisture buildup and keeps the roof cooler, which reduces the amount of heat that radiates into the space below. The intake and exhaust of air help to decrease the amount of energy required to heat and cool the space below because it allows the heated or cooled air to circulate throughout the space.
Fixing Attic Ventilation
Most building codes require at least some sort of roof venting since hot air cannot escape unless there is a way for it to escape. Hot air can escape from an attic space with a ridge vent installed.
We recommend ridge venting for almost all homes instead of box vents or wind vents. Air can escape the roof’s peak through the ridge vent, keeping the roof watertight while allowing air to escape.
Talk to a Roofing Professional
The ventilation needs of your roof must be discussed with a professional roofer before installing or improving one. It is imperative that your roof installer carries high-quality venting materials and that they are prepared to provide your roof with excellent ventilation.
There is more to roofing than what meets the eye!