The standard intake vent for attics is a soffit vent (also sometimes referred to as an “eave vent”) and it allows for air to enter the attic down low, near the eaves. Intake air is critical to maintaining a proper flow of air throughout the attic space. Air enters low and then escapes out of the attic higher up near the peak of the roof, usually via a ridge vent, an attic fan (which we do not recommend), static roof vents, or a high-mounted gable vent/fan. Remember, it’s a bad idea to mix exhaust vent types (passive vents with active fans). More info that here: Proper Attic Ventilation
Even without soffit venting, it is important to provide an air gap at the soffit level to help keep the roof deck dry. For more information on ventilation and moisture control, read this article I wrote on Proper Attic Ventilation. It’s my position that you should have a proper ventilation system in your attic and that you should always take the time to air seal the floor of the attic (sealing off the living space from the non-conditioned attic space), but in cases where you don’t (or aren’t able to), I want to offer some information and direction.
What do you do if your attic doesn’t have soffit vents and you are unable to add them?
First, let me reiterate that I think you should use soffit vents as your intake source for attic ventilation. If your house has minimal (or non-existent) overhangs that won’t accomodate soffit vents, or you simply aren’t able to install them for some reason, then you have a couple of options to provide intake air inlets low near the roof perimeter.
The two most common options are to:
- Install low gable vents located above the top level of the attic ceiling insulation
- Use “eye-brow” vents that are on the top of the sloping roof surface near the soffit/eave area.
- Focus on the other ventilation you have in the attic.
If you are installing a new roof, consider a drip edge vent. This will allow air to come in under the edge of the shingles, and then enter the attic via a small slot/cut that is about 8” from the edge. Learn more here.
Various exhaust vents can be used in conjunction with low gable vents and “eye-brow” inlets. For example, you can use ridge vents, mushroom cap vents, upper gable end vents/fans, high mounted attic fans, etc. Remember, your main goal is to get air moving through the attic by entering the attic space down low near the overhang/eave level and leaving the attic near the peak of the roof.
Using Gable Vents
For an attic without soffit vents, you may have the option to use gable vents instead. Typically you would have a gable vent on each end of the attic. Normal vented air likes to enter the attic lower down (near the bottom third of the attic ) and as it passes through, it will exit higher up near the top third of the attic space. If you have an attic with no soffit vents but 2 unobstructed gable vents, then you will probably be ok on ventilation. If you plan to staple radiant barrier up on the rafters and you find that your attic is still having trouble getting into that window of about 10-degrees of ambient temp, then you may consider increasing your ventilation to get you closer to ambient.
Using Low/Eyebrow Vents
If a gable vent seems like too big of a commitment or undertaking, consider smaller eyebrow vents that are mounted low on the roof slow so they can act as intake vents. Remember, you want more entry points at the perimeter (bottom) edge of the roof than you want at the exit points at the top of the roof. Most people have plenty of exhaust vents but not nearly enough *intake* vents.
Should You Add a Ridge Vent?
Maybe you’ve considered adding a ridge vent because you’ve heard they’re a good choice but you’re not sure since you don’t have soffits. Let me spare you the headache, if you don’t have soffits, don’t install a ridge vent. A ridge vents works by drawing air upward and out of the attic space. But if you have no intake, where is the ridge vent going to draw the air from? 9 times out of 10 it’s gonna come from your leaky attic floor. This is a huge energy waster that I discuss more in this article: Comfort and Energy Efficiency Tips.
Another option for homes that have no place for intake vents would be to use a modified solar fan. You will reverse the wires to make the fan blow INTO the attic as your intake. If you go this route, you will need additional vents to allow the air to get OUT (I recommend you use static vents for this purpose). This method is called “positive pressure ventilation” and should only be used as a last resort.
Do you need ventilation in order for radiant barrier to work? No. Radiant barrier does require and air gap to work to reflect heat, just an air space/gap. You can learn more about how that works here: Why An Airspace is Required for a Radiant Barrier.
Ventilation is important and can help keep an attic dry and lower air temperatures, but not having any ventilation isn’t the worst case scenario. If you don’t have soffit vents, we recommend you add some other vents in the lower part of the attic that can function like soffits. For some homes, you could try adding vents to a porch ceiling that could act like a soffit and feed the attic. If none of these options are possible, then we suggest you focus your attention to making sure the floor of the attic space is air-tight by checking ductwork (if applicable), lights/fans/vents protruding wires or hardware into the attic, and any other area of the attic floor where there are openings/holes/seams. A couple of cans of spray foam can go a long way toward helping keep things sealed up air tight.
Remember, what really matters is doing everything you can to make sure that the ceiling under the insulation has no air leaks into the attic, and this is a good practice whether or not you have attic ventilation!