Deciding whether or not to add that second (or third or fourth) system to a home can be tricky. There is no cut-and-dried rule that states exactly how many systems an application should have.

Of course you run load calculations, but what do you do when that doesn’t give you a clear-cut answer?

Usually, the decision is influenced by the contractor’s experience, as well as the configuration of the structure, how it’s used, how many windows it has, which way it’s facing, etc.

In some cases, contractors are using zoning rather than adding an extra system. Zoning manufacturers say that this is beneficial, because it can cut down on the cost of the installation.

That’s especially true if humidification, dehumidification, or electronic air cleaners are involved, as multiple sets of each type of equipment would then be required, resulting in higher initial costs as well as higher maintenance costs.

Others believe that using zoning rather than adding another system may sacrifice customer comfort, especially during peak periods and in larger residences — particularly if zones are not similar in size and location, as one zone may be calling for heating or cooling continually during peak periods. There’s also the potential problem of duct noise.

But multiple systems and zoning need not be mutually exclusive terms. Many believe that when used together, the customer will experience supreme comfort.

Zoning can save money

Ray Jetton, Jetton’s Hvac, Springfield, MO, is one contractor who believes that in certain situations, it makes more sense to install a zoning system than two units. “When we’re doing the insulation, we can cut down to one unit almost every time over two,” he says.

Proper insulation is an extremely important issue, says Jetton. He notes that some people think that plumbing, heating, and air conditioning go together, but he firmly believes that insulation and heating and air conditioning are better suited for one another.

“If you know the house is insulated well, you can do a better job on heating and air,” he notes. Jetton’s specializes in energy-efficient homes, and it always insulates the houses in which it places hvac equipment.

When his company insulates a house, Jetton is convinced that zoning can be used in place of multiple systems. “I want my customers to have premium comfort. People see that they can have the same comfort with one unit as opposed to two, and they have less potential for more mechanical equipment to break down, and it saves money by using less equipment.

“You do put more money back into the zone system and extra ductwork, but the occupants are much more comfortable,” says Jetton.

He cites as an example a custom home he’s currently working on. The 5,200-sq-ft home is distributed evenly on two levels, 2,600 sq ft on each level. Some of the main rooms upstairs have cathedral ceilings that stretch upwards of 14 ft, while the rest of the house has 10-ft ceilings.

“Because of my insulation and the computerized load calculation I did, I discovered I could put a 5-ton unit in that house. Since I would be pushing it with a heat pump, it was either go with two systems or zone it.”

He decided to zone it, reasoning that peak conditions in the Springfield area would only be reached about two or three weeks out of every year. With zoning, Jetton says he can direct all the cooling or heating upstairs or downstairs, or distribute it between both floors.

“That allows me a lot more play with the equipment that I’m able to use, and it sure gives the customer a lot better comfort, because they can control it in two different areas.”

Jetton adds that before zoning any application, contractors should be sure to put a lot of thought into it, as it’s not as simple as “slapping in two systems and leaving.”

With zoning, it’s necessary to make sure the ductwork is sized properly and that it’s insulated and sealed. Otherwise, there could be potential problems such as tripping the limit switches on the furnace or freezing up the coil.

Zoning complements multiple systems

Scott Droegkamp, general manager and president, Dave Droegkamp Heating, Hartland, WI, agrees that there are some applications in which zoning can work better than multiple systems. However, his company has adopted the philosophy that, generally speaking, any house between 3,000 and 3,500 sq ft will receive more than one system.

“We made a decision that as the homes got larger, we’d go with multiple equipment rather than zoning everything,” says Droegkamp. “When zoning first came out, people could keep the costs down and it was a great thing to get a job and put it in. But over the long haul, once people were living with that system, they just weren’t happy with the contractors.”

The challenging part of zoning multiple level homes, notes Droegkamp, is that it’s possible to end up with a small zone on the top floor, which will continually call for cooling during the warm summer months. In those cases, Droegkamp finds that it’s better to have multiple systems and then zone off of each system.

“I have found that zoning works well in a two-story saltbox house where the same square footage is directly above another one. It’s cost effective and it’ll work just fine for the customer over the years.”

But zoning everything isn’t feasible, says Droegkamp, simply because houses just aren’t built the way they used to be. For example, he’s run into homes where the second floor is larger than the first floor.

In those situations, he believes multiple systems leave the customer more satisfied. And to Droegkamp, satisfaction is everything. “You have to work hard for the customer’s trust these days. It’s so important to keep your name credible, to keep your company strong. You’ve got to bend over backwards for the customer today.”

For that reason, Droegkamp won’t work with just any builder. Sometimes he’ll lose a job because he won’t put in a system the cheapest way possible. He notes that builders often want contractors to put in larger equipment and zone it, in order to keep costs down.

He won’t deal with just any customer either. Through the school of hard knocks, Droegkamp has learned to walk away from those with unrealistic expectations about their hvac systems.

He cites several examples of people who didn’t want to make room for ductwork in their aesthetically pleasing homes. In those cases, he says you’re bound to lose money, because the customer will never be satisfied.

“As a contractor, you’re not going to keep everybody happy, but you’re going to try to recognize the ones you’re going to have problems with. It’s OK to say no.”