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Ventilation is one of those things that homeowners rarely think about, and many are even surprised when their roofing professional brings it up while discussing roof replacement or repairs. But proper ventilation plays a critical role in protecting your roof, extending its lifespan, and ensuring your home remains comfortable.
To help better familiarize you with roof ventilation, we’ll outline the types of roof ventilation components, explain some of the benefits they provide, and discuss basic roofing ventilation requirements below.
The Importance of Roof Ventilation: Why Is Roof Ventilation Necessary?
The notion of roof ventilation may seem a little counterintuitive at first. After all, shouldn’t your roof be designed to protect your home from the elements? Doesn’t ventilation stand at odds with this goal?
Not really. In fact, ventilation provides a number of important benefits for your roof and overall home. A few of the most important reasons that your roof needs some air exchange include:
Reduce Heat in Your Attic
In most places, a roof will be blasted by the sun all summer long. And here in the Charleston area, your roof even gets a ton of sunshine in the spring and fall too.
All of this sunlight can cause the temperature in your attic to soar, which can lead to the premature aging of your roof components (including the shingles, underlayment, and decking). It can also decrease the effectiveness of your insulation. And while rare, excessive attic temperatures may even present fire risks.
However, with proper ventilation components installed, the hot air in your attic will be allowed to escape, thereby keeping your attic temperatures lower.
Prevent Moisture from Accumulating
Cooking, showering, doing laundry, and even breathing all release moisture into the air in your home. And because your attic will tend to warm up more than the rest of your home, it will draw this moisture up into the attic via small cracks. And the hotter your attic is, the more moisture will be drawn up into it.
Once this moist air is in the attic, it will remain trapped there — unless you have ventilation components installed that will allow the damp air to escape and fresh, drier air to replace it.
The damp air itself is a problem, but it becomes even more problematic at night, when the temperatures drop. This causes the moisture to condense out of the air and form water droplets on your attic walls and other interior surfaces.
Stop Mold and Mildew Growth
The moisture that accumulates in your attic will cause a variety of problems, from increased heating and cooling costs to damaging anything you store up there. However, the biggest problem it may cause is that damp air encourages the development of mold and mildew.
Mold and mildew are not minor issues — they can actually represent serious health risks to your entire family. And unfortunately, mold and mildew problems can be very difficult and expensive to repair. You may even need to have your entire attic (and potentially your home’s ceilings) replaced.
But ventilation fixtures allow the damp air inside your attic to escape, which helps to prevent the growth of mold and mildew.
Maintain More Comfortable Temperatures
As you may have already realized, the warm, damp air in your attic will tend to make the rest of your home feel hot and muggy. This can obviously make your home uncomfortable, but it may even represent a safety hazard in places like Charleston, given our region’s incredibly high summer temperatures.
However, when roof vents are installed, this hot and humid air can escape outside. This helps to reduce the temperature and humidity level of your attic and keep the rest of your home cooler, drier, and safer.
Reduce Your Energy Bills
Comfort and cooling bills go hand in hand; if your home’s attic is excessively warm, your home won’t be very comfortable. This means you’ll likely turn down your air conditioning even further, which will cause your energy bills to go up.
Even if you don’t try to make your home more comfortable by lowering your AC temperature, your HVAC unit will have to work harder to keep your home at any temperature you set when your attic isn’t properly vented. But proper ventilation will help to keep your attic cooler (and drier), which will help keep your energy bills manageable.
It’s also worth pointing out that non-vented attics will force your home’s HVAC unit to work harder. This will shorten its lifespan and force you to have it replaced more quickly — something that’s certainly not inexpensive to do.
Prevent Ice Dams from Forming
Though we don’t get a lot of snow and ice in Charleston, we get winter precipitation every once in a while. And when this happens, it can cause something called an ice dam to form on improperly vented roofs.
Ice dams form when ice or snow on your roof melts and drips down toward the edges. But because the eaves of the roof are typically cooler, the water may refreeze when it reaches the eaves. This will cause the melting water above it to become trapped and ultimately lead to the formation of large ice blocks, called ice dams.
But properly ventilated roofs help ensure the various components of your attic and roof remain roughly the same temperature. This helps prevent the ice from forming along the eaves and edges.
Understanding How Roof Ventilation Works
The principles behind roof ventilation are pretty simple. Essentially, roof ventilation components allow warm and damp air to escape from your attic, which in turn allows fresh, cooler, and drier air to replace it. This is accomplished using two types of vents: intake vents and exhaust vents.
To maximize the efficiency of the ventilation system and take advantage of the natural way air flows (hot, warm air tends to rise), these vents are generally placed in specific places. Intake vents are usually installed at eaves or soffits, where the air is coolest. By contrast, the exhaust vents are usually located near roof ridges, where the temperatures are highest.
General Ventilation Requirements
While the specific building codes enforced in various municipalities vary a bit, most areas have similar ventilation requirements.
Typically, you’ll need 1 square foot of ventilation for every 150 square feet of attic space. In other words, if you have a 400-square-foot attic, you’d need 2.67 feet (or 384 square inches) of ventilation space. And because most building codes require the intake and exhaust ventilation to be equal, you’d need 192 square inches of intake and 192 square inches of exhaust.
However, in some cases, with a balanced intake-exhaust system in place and a vapor barrier installed on the warm side of the ceiling, you can use less ventilation than this. It is sometimes acceptable to reduce the ventilation requirement to 1 square foot of ventilation space for every 300 square feet of attic space.
In all cases, you’ll want to discuss the issue carefully with your roofing professional to ensure your roof features a ventilation system that’s capable of keeping your attic cool and dry. It’s also important to check the warranty information for the roofing system you’re installing; some roofing systems have minimum ventilation requirements you must follow to avoid voiding the warranty.
Common Types of Roof Vents
No two roofs are exactly the same, so every home’s roof ventilation system should be custom designed to offer the best possible air exchange. But while your roof’s design, the type of shingles you have, and your attic’s layout will all play a part in determining the ideal roof ventilation system, most homes will use some of the following types of vent components:
Intake Vents
- Soffit Vents: Soffit vents are the most commonly used intake vent style, and they are typically installed under the eaves (the part of the roof that overhangs the wall). They draw in cool outside air and allow it to flow upward into the attic.
- Edge Vents: Edge vents are installed at the lower edge of the roof, right above the gutter line, and under the shingles. They’re typically the choice for houses without soffits or those with very narrow eaves that don’t offer enough space for soffit vents.
- Over-Fascia Vents: Over-fascia vents are installed on top of the fascia board, underneath the starter course of shingles, and behind a home’s gutter system. They too, are often used in homes that lack enough soffit space for traditional soffit vents.
Exhaust Vents
- Ridge Vents: Ridge vents are placed along the peak (ridge) of a roof and allow warm air to escape from the highest point of the attic. They’re most effective when used in conjunction with soffit vents.
- Box Vents: Box vents or roof louvers are simple vents installed near the ridge. Because they don’t feature moving parts and rely on the natural rising action of warm air, they are also called static vents.
- Roof Turbines: Sometimes called whirlybirds, Roof turbines are semi-mechanical vents that spin with the wind. This creates a vacuum effect, which helps to pull hot air out of the attic.
- Powered Attic Fans: Powered attic fans are like room fans in a way, as they actively pull hot air out of the attic using a motor. These kinds of vents are often mounted on the roof or gable wall.
Signs of Poor Ventilation
If you’re having a roof repaired or replaced, your roofing contractor will likely discuss your home’s ventilation needs and ensure that you end up with enough air exchange in your attic. But what if you’re not considering repairs or replacements right now? How can you tell if your roof features sufficient ventilation?
You can consider the general guidelines described previously (1 square foot of ventilation for every 150 to 300 square feet of attic space), but you can also simply look for signs that indicate poor ventilation. A few of the most important include:
- Hot, stuffy attic air (particularly in the summer)
- Noticing mold or mildew odors while inside the attic
- The appearance of condensation or ice on rafters in winter (rare in Charleston)
- Seeing signs of shingle curling
- Finding that your shingles are prematurely aging
- Excessive energy bills
- Experiencing frequent HVAC system problems
If you notice any of these signs or symptoms, you’ll want to discuss your roof’s ventilation system with a professional roofing contractor.
Ventilation and Roof Replacement
If you’re having your roof replaced, it’s the perfect time to review your ventilation setup. Roofing contractors should evaluate whether your current system meets code — and your home’s needs. Adding or adjusting vents during a re-roof is easier and more cost-effective than doing it later.
Some manufacturers even require proper ventilation to honor their roof warranties. Skipping this step could leave you on the hook for repairs down the line.
FAQ: Home Roof Ventilation
Still have questions about your home’s roof ventilation needs? We’ve rounded up a few of the most common questions we hear from customers and answered them below!
What is the best roof ventilation method?
The best type of roof ventilation for your specific home will vary based on a variety of factors. However, a combination of soffit vents for intake and ridge vents for exhaust is usually a winning combination. However, powered attic fans can provide even more ventilation when space, circumstances, and budgets allow.
Do you really need roof ventilation?
Absolutely. Without adequate roof ventilation, your roof will age faster, your cooling bills will skyrocket, and you may start having mold or mildew develop in your attic. Proper roof ventilation is also required by local building codes in most areas.
What ventilation is required for a roof?
The exact ventilation requirements vary from one place to the next, but 1 square foot of ventilation for every 150 to 300 square feet of attic space is usually a good guideline. You’ll simply want to speak with your roofing contractor to determine the precise ventilation needs for your home.
How can you ventilate an existing roof?
If your home lacks sufficient ventilation or you’d simply like to enjoy the benefits of adding more attic airflow, contact the professionals at Willow Ash Roofing. We can install a variety of roof ventilation systems, which will help protect your roof and keep your home more comfortable.
Ensure Proper Ventilation with Willow Ash Roofing
Whether you’re in need of only minor roofing repairs, you need a completely new roof installed, or you’re simply concerned that your roof doesn’t have enough ventilation as is, you can trust the professionals at Willow Ash Roofing to provide the guidance and unbeatable roofing and ventilation services you need. Contact us now to arrange for a free estimate and on-site ventilation inspection. We’ll discuss the ventilation requirements for your roof with you and provide recommendations if you would benefit from having more ventilation installed on your roof.
