There’s a lot of misinformation about attic ventilation, so we wanted to take a moment to clear up any confusion about how you should be venting an attic and what you need to do it right.
1. If I have roof vents, I have ventilation.
If only it were that simple! Attic ventilation should have a balanced amount of both air coming in to the attic and air exiting the attic. (It’s ok if you have a little more air coming in than you do going out. For example, lots of soffit venting.) The main way air enters attics is via soffit venting. These vents allow cool, dry air to enter the attic at its lowest point and as air travels up and out the higher points (ridge, turbine, gables) so that the airflow removes warm, moist air from inside the attic. For exhaust you can have a ridge vent, a static roof vent, a turbine (whirly bird) vent or gable vents. Some people have powered attic fans or solar fans, and those are ok too. Just beware of mixing passive and active venting in an attic – that’s a bad idea!
2. More ventilation is always better.
Too much of a good thing can be a bad thing. I recommend you choose one type of exhaust vent and go with it. Ventilation is simple because air always travels the path of least resistance. When you mix exhaust vents on a roofline, the strongest vent will overpower any passive venting and then pull air in from any nearby exhaust vents! This disrupts the normal path of of air coming in the bottom and out the top and defeats the whole purpose of having low/high vents.
So while it’s generally a great idea to have plenty of soffit vents for intake, having too many exhaust vents or mixing exhaust vents can counteract your goal of cooling the attic air temperature.
3. The best way to get air moving in an attic is by using powered vents.
This idea flows from the one above and I’d just like to reiterate that a passive ventilation system will work just as well (and for free) as a powered (active) ventilation system. You’ve heard me say that I don’t typically recommend the use of any sort of powered fans and the top reasons why I feel that way, besides that they work just as well as passive vents, is because of 1) cost, 2) noise, and 3) some only work on sunny days!
Many people may not realize that it’s usually fairly breezy at the top of a roof. Standing down on ground level, you’re blocked by fencing, homes, etc but up top without obstructions, there’s a good amount of air flow. Just a little breeze moving can turn wind turbines and allow them to effortlessly pull out as much air as an electric fan can.
What if you already have fans? Not to worry! Again, fans work and won’t be a problem as long as you feed the fans with plenty of intake air. So take some time and check on your soffit vents. If they’re not cut out, get them cut out. If they’re blocked, clear the path and maybe install some baffle vents. If they’re dirty, clean them! Dirty soffit vents are actually the leading cause of attic ventilation problems and so much so that I made a video to help show you how you can clean them yourself and get things back on track with airflow in the attic.
Don’t neglect giving the fans a source of intake because without it, the air in your attic will depressurize and it’s likely going to result in air from inside your home getting pulled into the attic space via light fixtures or other ceiling penetrations. The net result is that your home feels warmer faster, and your air conditioner has work harder than ever just to try to keep things comfortable (ie. huge energy waster!).