Six things get checked when one part of a house will not behave. They are the same six every time — but the order changes completely depending on what is actually wrong, and so does where zoning belongs in it.
Upstairs too hot in summer
This is the most common complaint in Huntington and it is almost never a zoning problem. A second floor that bakes in August is usually being beaten by two things at once: ducts running through a roasting attic, losing air and gaining heat on the way to the bedrooms, and a roof and an attic that are not holding the sun out.
Zoning divides the cold air you already have. If half of it is being lost into the attic before it arrives, dividing what is left changes very little — and you will have paid for dampers, a controller and a second thermostat to find that out.
Upstairs too cold in winter
This one is worth stopping over, because heat rises — a second floor that is colder than the first in January is behaving oddly, and that means something specific is wrong rather than something general.
In our experience it is a damper, a closed branch or a genuine airflow restriction far more often than it is a capacity problem. It is also the case where the cheapest checks have the best hit rate, which is why they are at the top of the list.
One room that is always wrong
A single room out of step with the rest of the house is a delivery problem, not a system problem. The system is evidently capable — every other room proves it — so the question is what is happening between the plant and that register.
Very often the room was added or converted: a garage, a porch, an attic, an extension. Those are exactly the places where a branch was taken off a trunk that had nothing spare, or where a run was squashed to get it through a joist bay.
Two people, two different temperatures
This is the case where zoning genuinely goes first, because nothing else solves it. Every other item on the list makes a house more even — and an even house is exactly what you do not want when one person wants the bedrooms at 65 and the other wants the living room at 72.
The checks below still matter, because a zoned system inherits every fault the unzoned one had. But here they are things to do alongside zoning rather than instead of it, and a contractor who tries to talk you out of zoning on this complaint is not listening.
The six checks, in the order that suits it
With JavaScript off, the list shows the summer order and all four verdicts above are visible.
-
1
What the ducts are losing
Ductwork running through an attic or crawlspace leaks air out through every joint, and the joints were taped by somebody kneeling on insulation thirty years ago. In summer it is worse than a loss: the air that does arrive has been sitting in a 130°F attic on the way.
Sealing is cheap next to equipment and it works in both seasons at once. It is also the only item here that improves the house whatever else you decide to do. -
2
Insulation, air sealing and the attic
Not a heating question, strictly, which is why it gets skipped. But a bedroom under an uninsulated roof with a gappy hatch and recessed lights venting into the attic is losing a fight that no amount of equipment wins.
Where this is the real cause we will say so, and it is not work we do — an insulation contractor is the right call, and it is usually the cheapest thing on the whole list. -
3
The return, not the supply
Almost every uneven house we measure has more supply than return. Everybody looks at where the air comes out; hardly anybody looks at where it gets back. Air that cannot leave a room cannot keep arriving in it, which is why a closed bedroom door can undo a system that works fine with the door open.
Adding a return, or a transfer path over a door, is frequently the single most effective thing done to an uneven house — and it costs a fraction of zoning. -
4
Measure what you actually have
Total static pressure across the system, then airflow at the register that is wrong and at one that is fine. Two instruments, half an hour, and the argument is over.
Without this everything else is guesswork, including ours. High static pressure means the system is fighting the ductwork, and adding zone dampers to a system already fighting its ducts makes it worse, not better. -
5
The dampers you already have
Most ducted houses have balancing dampers in the branches near the plant, and in most houses nobody has touched them since the day they went in — or somebody closed one for a reason that no longer exists and forgot.
Free, if they are accessible. It will not fix a house that is genuinely short of air, but it costs nothing to find out and it occasionally ends the whole conversation. -
6
Zoning
Motorised dampers in the trunks, a thermostat per zone, a controller, and usually a bypass or a variable-speed blower so the system can cope when only one zone is calling. Done properly on a suitable system it works well and it lasts.
It divides the air you have. It does not create more, it does not seal a duct, and it does not insulate a roof. On a system with high static pressure or heavy duct leakage it will underperform, and the parts of it that fail — actuators, a controller — are parts a future contractor has to know about.
Three things people are told that are not quite right
“Close the vents in the rooms you are not using”
Closing supply registers raises static pressure across the whole system, which pushes more air out through the leaks and makes the blower work harder. On a modern high-efficiency furnace it can trip the limit. It rarely helps and it sometimes hurts.
“You need a bigger unit”
An oversized system runs in short bursts, never long enough to move air round the house or to pull moisture out of it. The usual result of oversizing a house with an uneven-temperature problem is a house with an uneven-temperature problem and a bigger bill.
“A smart thermostat will sort it out”
A thermostat measures the room it is in and switches the system on and off. A second thermostat without dampers controls nothing extra. Good thermostats are worth having; they do not move air to a room that is not getting any.