Find out how to maintain your cooling and heating systems to ensure they will run properly when you need them most. Get tips on cleaning the furnace, sealing your ducts, replacing the filter and other maintenance tasks.
TOM: Well, why does it always seem like your heat conks out in the middle of winter or your A/C quits on the hottest day of the year? If you don’t take care of your system, that’s exactly what can happen. Staying on top of heating and cooling maintenance will also help your systems run more efficiently and last longer.
RICHARD: Nice to be in The Money Pit again.
TOM: It’s a pleasure to have you, my friend.
And we usually ignore the HVAC system until something goes wrong. But that’s the worst thing you can do. This is a system that truly needs regular care and feeding, right?
RICHARD: Absolutely. Problem maintenance is not difficult or costly and it can really save you a lot of trouble in the long run. It has to run all winter and if you don’t maintain it, it’s not going to take care of you.
TOM: So let’s talk about the reason that it needs maintenance. Burning fossil fuel just like running a car. If you don’t tune it up, everything gets dirty, gunked up and it can actually be unsafe.
RICHARD: That’s right. Every time that burner fires, it’s a little bit of incomplete combustion and so, sooner or later, for any fuel – gas or oil – it does have to be serviced and cleaned.
TOM: So if we hire a service pro, I’m sure that there are as many variations of what they actually do as pros out there. What are the core steps that a pro is going to take to make sure our system is efficient for the season and safe?
RICHARD: Well, one is to make sure that you’re burning the fuel the most efficiently. So that would be the cleaning of the furnace, checking the burner to make sure it’s firing correctly.
The next is to be sure it’s being delivered to the building correctly.
RICHARD: Now, you’ve got ducts all through the building; those ducts should be sealed . It’s amazing to me how many ducts are put together without any duct sealer and maybe use a little bit of duct tape. So a fair amount of the heat or air conditioning, in cooling mode, that you’re making is not being delivered up to the living space. It’s going into the basement, it’s going into the walls, it’s going to the attic: the places where you don’t need it.
TOM: Now, let’s – let me stop you right there because that’s a really important point. I think one of the core differences between the way we used to put ducts together and the way we do it today is that issue of duct sealing . And we’re talking, of course, about the sealing of the joints of the ducts. If you don’t seal them properly, as you say, all that conditioned air is going to escape. What are a couple of the options if you have an older house and you want to seal those ducts? Most people are going to grab a roll of duct tape but duct tape isn’t the best thing to use on ducts.
RICHARD: Biggest misnomer in the entire industry. The last place you would want to use duct tape is on a duct.
TOM: The adhesive just dries out and falls off.
RICHARD: That’s right. So my preferred method is a duct mastic. It comes in a tub, like paint; it’s sort of like a putty, almost. It’s not quite a paint; it’s a little thicker than putty. It’s a pain in the neck to work with; it gets all over you. But you take a brush and you paint all the seams, both the seams where the ducts come together and on the sides of them. And you make sure that all of the air stays in there and that’s an elastic – elastomer sort of …
TOM: So it expands and contracts with the duct itself.
RICHARD: That’s right. And so it won’t crack.
And the other is these foil tapes. Many of them have a rubberized backing on it that has got a great adhesion to it. You put that onto the ducts and the air stays in the duct.
TOM: Now, that’s something you only have to do once, thankfully.
RICHARD: Absolutely. Absolutely.
TOM: But back to the steps of the service. What about filters? That’s another thing that people seem to ignore. I remember in the years I was a home inspector, I would see these incredibly dirty blower compartments on furnaces and then a brand-new filter, obviously just stuck in for the inspection itself.
RICHARD: That’s right.
TOM: This is something that truly has to be replaced on a very regular basis.
RICHARD: You can’t change the filter enough, in my opinion. And it becomes mostly a function, though, of the amount of contaminants in the house. If you have pets, with pet hair and dander, they should be changed regularly. At the least case, they should be changed before the start of each season, before heating season and again before cooling season.
TOM: Now, speaking of cooling season, what additionally do you have to do to service your cooling system?
RICHARD: Well, you want to make sure that the cooling coils – the place where the air goes across, if you ever looked inside any of these, it would be like aluminum fins. And you want to be sure those are clean as a whistle. And so, if there’s algae or any sort of mold buildup, a good service tech would be sure to do a coil cleaning to be sure that the air going across that coil is picking up all that cooling power or the heating power in heating mode.
You also want to make sure the refrigerant level is correct on your air conditioner. You know, nowadays, any good service tech knows how to read his refrigeration gauges. The proper amount of refrigeration is critical. Too much refrigerant doesn’t help you and too little doesn’t help you. So you need somebody that knows what they’re doing.
TOM: Now, what about the blower? Anything to adjust with the blower itself?
RICHARD: You can. Most of these blowers are designed to be matched to the furnace that they’re actually coming in.
RICHARD: There’s not a lot of changes. There’s one thing that’s very interesting in the furnace industry, though, and that’s a thing called an ECM blower motor: electronically commutated motor.
TOM: And how does that work?
RICHARD: And with that, that blower fan, instead of just being at one speed, can actually change in according to how much resistance is out there. So, as zones or dampers are opened or closed, the fan will reflect that and sort of cruise control up or down to match. And it saves a lot of electricity.
TOM: So that’s something that you might want to consider if you’re doing a retrofit.
RICHARD: That’s right.
TOM: Speaking of retrofits, when does it make time to change out an old furnace or an old air conditioner  with one that’s newer and far more efficient? Do you wait until it fails? Do you wait until it becomes unsafe? I mean many times, I remember folks only replacing furnaces when the heat exchanger cracked.
RICHARD: Well, I think you – some of the things that affect that decision is the cost of fuel. And if you have a furnace that’s been in there for a long time and if it, on its best day, was 75-percent efficient – and now you have a furnace you can put in that would be 95-percent efficient.
Well, that’s an important number because as fuel goes up, if I can save 25 and 30 and 40 percent on my fuel bill, there’s really no better place to put money nowadays. If you had $10,000 to put into a bank, what would you – you can’t get any return on that, right?
TOM: That’s true.
RICHARD: So if I could do something that could avoid a major cost each winter and every winter it gets better and better as fuel goes up, then it’s a great investment. Most people don’t do it, though, until it breaks. They say it’s not the romantic part of the house. They just say, “Well, I’ll wait for it to break.”
TOM: Now, there is one thing that you can do, even if you have a small budget, that is guaranteed to save you a lot of energy and that is to replace your standard thermostat with one that’s a setback thermostat, correct?
RICHARD: Yeah, a clock thermostat. Let’s not heat the building or cool the building when people are not there.
TOM: Makes a lot of sense.
RICHARD: That’s right.
TOM: Richard Trethewey, the plumbing and heating contractor on TV’s This Old House, great advice. Thanks so much for stopping by The Money Pit.
RICHARD: Thanks for having me.
LESLIE: And remember, you can watch Richard and the entire This Old House team on This Old House and Ask This Old House on your local PBS station.
TOM: And This Old House and Ask This Old House are brought to you by Lumber Liquidators. Lumber Liquidators, hardwood floors for less.