Powered Attic Ventilation

When I first started in the trade, I used to advise customers with hot attics to install powered attic ventilators (PAVs) to “suck” that hot air out of the attic. It just made sense to me at the time; if the attic is hot, get the hot out!

When I started learning more about design, someone enlightened me that when you blow air into a space, the same amount has to go out, and when you suck air out of a space (like an attic), it has to come from somewhere. Ideally, the air would come from soffit or gable vents, but in most houses, there are also many gaps from the attic into the home, and a lot of that air will come from the inside and waste energy.

Nowadays, I'm a “fan” (pun intended) of either encapsulating and conditioning the attic or using large, well-vented soffits (will often require baffles to keep the insulation out) and ridge vents.

My friend Neil Comparetto just made a video on this topic that illustrates it nicely:

Comments

Related Tech Tips

Balanced Port TXV
  I walked into a supply house the other day and looked at a “universal” expansion valve on the shelf. The friendly guy behind the counter saw me and walked over. After saying hello, he said: “That's a great valve; it's even balanced port.” Now, I am a bit of a troublemaker. I should have […]
Read more
EcoBee Thermostats and Dehumidification
  Dehumidification features have been common on residential systems ever since the introduction of variable speed blower motors. The system is set up so that the blower can produce less CFM per ton when the latent load (humidity) in the space is higher than the setpoint relative humidity. Slowing the blower increases moisture removal by […]
Read more
5% vs. 15% Silver Solder (Brazing Rod)
First, let's get something straight: BRAZING is when you use a filler rod that isn't the same material as the base metal but melts ABOVE 840°F. Soldering is the same but at temperatures BELOW 840°F. With HVAC rods melting at around 1200°F, it confuses me why we usually call it “silver solder” but also often call it […]
Read more
loading

To continue you need to agree to our terms.

The HVAC School site, podcast and daily tech tips
Made possible by Generous support from