Getting Fresh Air Into an Air Tight House

  • How an air exchanger works. (Diagram courtesy of Matt Grocoff)

For the past couple of years, we’ve been visiting Matt Grocoff’s house in Ann Arbor. He’s been working to make it the oldest net-zero home in America. That means when he’s finished, the house should produce as much energy as it uses. Lester Graham has an update:


Matt Grocoff’s home is 110-years-old. It was originally heated by coal… and had no insulation. Coal was cheap… so you could stoke that furnace all day long without much worry about heat escaping. These days energy is more expensive… and there are concerns about using fossil fuels that emit greenhouse gases that cause global warming.

So, Matt is heating and cooling his house using a geo-thermal system. It uses a fraction of the energy that a gas or electric furnace would use. And… I’ve watched as Matt as worked to seal up every nook and cranny of the house. From attic, to walls, to windows to basement he’s insulated, caulked, used spray foam or found some other way to seal up his home. But… with everything so tight… he’s now got a bit of a problem. If it’s closed up, as during the winter, not enough fresh air can get in like it used to through drafty areas. That can cause the air to get stale.

MG: “A phrase I heard was ‘Insulate tight and ventilate right.’ If you’re sealing up your house so tight you’re no longer getting good quality fresh air in there, you’ve got to provide some mechanical ventilation when you’re running your air conditioner or heating system.”

LG: That would seem to defeat the purpose to me because now you’re going to be using electricity to ventilate a house because you’ve gotten it so tight.

MG: “Ahhh, that’s exactly where the energy recovery ventilator comes in. In a normal house what you’ll have is like a little bath vent that’s going to be sucking the stale air out of your house. But, with that stale air, you’re also blowing right out through your roof vents really warm, conditioned, expensive-to-heat air during the winter time. With the energy recovery ventilator, you can actually recover some of that lost energy and pay for the energy that it’s costing to run those fans.”

The energy recovery ventilator is not that big. It fits in a small space in his attic. It works kind of like a heat pump. As the contractor, Doug Selby explained it to me… it draws air out, but before it goes outside, the unit recovers much of the heat… and it’s the heat that costs you.

DS “With an energy recovery ventilator or a heat recovery ventilator, you can recapture up to 95-percent of the energy that you’ve already paid for once. And you can do that infinitely. The fact of the matter is, yes, these homes do need to breathe. But, the worst way you can do it is just by having an uninsulated, loose house that loses most of its energy out the attic and out the basement. And, you still end up with poor interior air quality and you’re not getting any benefit from that from an energy standpoint.”

So, you get fresh air… but you recycle almost all the heat.

Matt Grocoff says he’s spent quite a bit of money during the past couple of years reducing his energy consumption… but he looks at it as an investment. He says he’ll save money at a rate that’ll out-perform the stock market. In other words… the money he’ll save on energy costs will pay back the cost of the equipment and then some.

Now,he’s about to change gears. All this time he’s been working to reduce his energy usage. The next step… he’s going to produce energy.

MG: “Yes, we are now ready for solar panels because we will be efficient enough to produce more energy than we consume.”

LG: That’s Matt Grocoff with Greenovation-dot-TV. I’m Lester Graham with The Environment Report.

HOST TAG: The next time we visit Matt… we’ll bring you the story of putting up those solar panels… the final chapter of his work to become net-zero.
That’s the Environment Report for today. I’m Rebecca Williams.