Ventilating an Attic

Learn why adding an air conditioning duct in the attic is not recommended. Find out the best method of cooling your house without venting into the attic, and which vents to install to cool your home.

LESLIE: We’re on our way to Nevada where Rod listens to The Money Pit on KBZZ and you’ve got a swamp cooler. I didn’t know there were swamps in Nevada.

ROD: (chuckling) Thank you.

TOM: (chuckling) How can we help?

ROD: Actually, I do have air conditioning but I was thinking to lower my utility bill, I might put in a evaporator cooler …

TOM: OK.

ROD: … and duct to the bedrooms. My question for you today is what about if I also duct it to the attic? Would that help to keep the house cooler if I get the attic cooler?

TOM: Oh, you want to air condition the attic?

ROD: Well, I want to get it cooler. If that would help keep the house cooler.

TOM: Yeah, it’s going to cost you a ton to do that, too. No, that’s kind of a silly way to do it. I was stretching – I was trying not to offend you but Rod, not a good idea. Here’s what you want to do.

First of all, your attic needs to be as ventilated as possible. So, in your house, you want to make sure you have a continuous ridge vent that goes all the way down the peak of the roof and then a continuous soffit vent so that all of the soffits are open and the ridge is open so that the attic is continually flushed with ambient air. Once you have the attic as cool as possible, you’re done in the attic. The attic is an unconditioned space. Air conditioning is for conditioned space, which basically means it has to be …

LESLIE: Insulated, drywalled; you know, finished.

TOM: I would not recommend adding an air conditioning duct in the attic. That’s not going to help you. I would recommend ventilating the attic and then make sure you have adequate insulation to keep the hot side hot and the cold side cold. Does that make sense?

ROD: Oh yeah, it does. If I put an attic fan in there, does it blow air in or blow air out?

LESLIE: It sucks air out.

TOM: And it won’t stop there. It’ll reach down into your house that you’re paying to air condition and it will suck cool air out of that, too. That’s why we don’t recommend attic fans; just passive ventilation.

ROD: OK, I appreciate it.

TOM: Alright, Rod. Thanks so much for calling us at 1-888-MONEY-PIT.

LESLIE: You know, I think it’s so funny, Tom, that we took a call from Rod in Nevada about an attic fan. Because normally we refer to your attic as the Las Vegas of your house. (laughing)