How a Home Energy Audit Works: Finding Your Heat Leaks

LESLIE: Don in Pennsylvania has got a question about his heating system. What can we help you with?

DON: Yes. I was wondering about a cold-air return – the fresh air return from the – bringing air in from outside …

TOM: OK.

DON: … the duct work.

TOM: Mm-hmm. You mean, from the exterior. You’re not talking about the return inside the house. You’re talking about venting some fresh air into the house, correct?

DON: Yes. Into the cold-air return ventilation system.

TOM: OK. So, I think what you’re talking about is called an air-to-air heat exchanger and …

DON: OK.

TOM: … basically it takes fresh air into the house but allows some of the heated air, as it’s being exhausted – sort of the stale air – to transfer some of its heat to the chilly air coming in and dramatically improves the efficiency of that operation. That’s added typically in a home – a residential home that’s really, really well-insulated [1]; that does not have a lot of air changes per hour, because it maintains the healthy environment. It’s also a fairly standard thing done in a commercial installation, where you have to make sure that you’re always introducing fresh air into the building. So it’s a good idea if the home is very, very tight. If it’s not really tight, then you don’t need to worry about it.

DON: OK. It is a little bit tight.

TOM: Well, how do you know how tight it is? Have you ever tested it?

DON: When I was up in the attic up there, we had the insulation running through the – through the wrappers and across.

TOM: You know, that may seem like it’s an energy-efficient house but we’re talking about how well-sealed the house is. There’s one way for you to tell; it’s called a blower door test [2]. It’s done by an energy auditor [3] and they can actually measure how tight your house is. And I’ve got to tell you, of all the times I’ve seen these tests done – basically, what they do is they stick a big fan in the front door and they blow the house up with air just like you’re inflating a balloon and then they measure how much of it is leaking out and they can actually do it in the reverse, too; they can depressurize the house and measure how much air is leaking in.

Generally, you will find that it’s very, very inefficient; far more inefficient than what you thought it was. So unless you’ve done that type of test, Don, I wouldn’t recommend that you install the air-to-air heat exchanger; just speculating that you may need it. I would get the data first and, frankly, if the house is leaky, you may be better off putting your money into how – in trying to figure out how to make it tighter and that’s something that will also be identified by that blower door test because it will show you exactly what’s leaking; whether it’s the windows, the doors, the walls, the outlets and you’ll know exactly how to attack it and make that house nice and energy-efficient [4]. You can probably get it done, by the way, by your local utility company. They very often offer those services.

LESLIE: Mm-hmm, and sometimes they even do it for free.

TOM: That’s true; sometimes they do do it for free. Don, I hope that helps you out. Thanks so much for calling us at 888-MONEY-PIT.