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Your house is four years old and it does not cool properly
This is the commonest call we get in Williamson County, and the equipment is usually the part that is working. Pick the symptom and how old the house is.
Start with what a builder-grade system actually is. It is not bad equipment. It is ordinary equipment, sized from a calculation that may or may not have been done properly, connected to ductwork installed by a crew working to a schedule in a house with no ceilings in it yet. The equipment is inspected before it leaves a factory. The ductwork is assembled on site, in an attic, at speed, and nobody measures it afterwards.
That is why the answer to “this house has never cooled properly” is so rarely the machine outside. A crushed flexible duct, a return that is one size down from the drawing, a supply run that was never connected at the boot, a bonus room with no return path — each of these produces symptoms that look exactly like an undersized system, and each is far cheaper to put right.
Everything below is written out in full. If you would rather read the whole thing, nothing is hidden from you.
A house under a year old is almost certainly inside its workmanship warranty, and a duct problem in a new house is workmanship. Put it in writing to the builder’s warranty department rather than ringing the trade — an email creates a date, and the date is what matters if this drags on. Describe what the house does, not what you think is wrong: which room, what time of day, what the thermostat says and what a separate thermometer says in that room. We are glad to measure it for you and give you the figures to attach, and we will say plainly if we think the builder should be doing the work rather than us.
One room is always hotter
Four causes, and they are cheap to tell apart.
- A crushed or kinked flexible duct. The single commonest one. Flex is easy to pull tight around a truss or to lay over a joist with a sag in it, and both cost you most of the airflow to that room.
- A supply that was never properly connected. The boot at the ceiling looks fine; the duct behind it has come off the collar or was never taped. You are cooling the attic through that register.
- No return path. If the door is shut and there is no return or undercut, air cannot leave the room, so it will not come in either. Bedrooms and bonus rooms, almost always.
- A damper somebody set in 2019. Worth checking first because it costs nothing.
What settles it is a measurement at the register and a look in the attic. Half an hour, and it usually ends with a length of duct being reworked rather than anything being bought.
The house loses ground on hot afternoons
This is the one that gets diagnosed as “undersized” and it usually is not. A system that holds the house all morning and slips two or three degrees between two and six in the afternoon is running at its limit, and the question is why the limit is where it is.
Leakage on the return side in a 130-degree attic will do it on its own: the system is spending part of its capacity cooling attic air it should never have been given. Low airflow from restricted ductwork will do it. So will a coil that is dirty on the inside face, which is invisible from the service panel and is common in houses finished with construction dust still in the air.
It genuinely can be sizing — but that is a finding you reach after measuring, not a starting assumption. It is also worth saying that no system holds a house on the worst two days of a Texas August without running continuously, and continuous running at design conditions is correct behaviour rather than a fault.
Cold, but it still feels damp
This is the signature of an oversized system, which in a new house is a great deal more likely than an undersized one. Cooling and drying are two separate jobs and the drying only happens while the machine is actually running. A system that satisfies the thermostat in eight minutes never runs long enough to pull moisture out, so the air is cold and heavy at the same time.
The other source is return-side leakage, which drags humid attic air into the system continuously. In a house with a slab and few openings, that can be most of the moisture load.
The fix is rarely a new system. Sealing the return side, correcting airflow so the coil runs at the right temperature, and in some cases a control change that lengthens run times will do more than replacing equipment, and cost a fraction of it.
The vents whistle or roar
Noise at the registers is static pressure, and static pressure is the most informative number nobody measures. It means the blower is pushing against more resistance than it was designed for — ductwork that is undersized, a filter grille that is too small for the airflow, a filter far denser than the system can carry, or flex runs with too many bends.
It matters beyond the noise. High static pressure reduces the air delivered, which reduces capacity, which makes the house uncomfortable and makes the system run longer for the same result. It also shortens the life of the blower motor and, over time, the compressor.
A static pressure reading takes ten minutes and tells you immediately whether the problem is the duct system or something else. It is the first thing we do in a noisy house and it is the measurement most often missing from any previous visit.
Comfortable, but the bills are high
The most interesting version of the problem, because the house feels fine and so nobody investigates. The system is achieving comfort by running far more than it should.
Duct leakage is the usual reason — air you paid to cool going into an attic, and hot attic air coming back in to replace it. It is invisible, it does not make a noise, and it is measurable to a number. A duct leakage test gives you a figure you can act on and compare against after any work.
If the house has electric auxiliary heat with a heat pump, the winter half of the bill is worth a separate look: a thermostat set to recover quickly each morning will bring the strip heaters on every mild day of the winter, which is an expensive way to save four minutes.
And before any of that, check the obvious: a filter nobody has changed, a register somebody closed, and whether the thermostat is doing what you think it is doing.
Under a year old
You are in the strongest position you will ever be in, and the thing to protect is the paperwork. Most Texas builder warranties follow the familiar one-two-ten pattern — roughly a year on workmanship, two years on the delivery systems including ductwork and distribution, ten years structural — but the pattern is not the rule; your own warranty document is, and it is worth twenty minutes of reading.
One thing worth knowing: there is no state body in Texas that enforces a builder warranty on your behalf. It is a contract between you and the builder, which makes written, dated, specific requests much more valuable than phone calls.
One to two years old
Workmanship cover has usually run out, but the delivery-systems period often has not, and ductwork is typically part of that. This is the window in which a great many people give up and ring a contractor without checking — read the document before you spend anything.
It is also the point at which a measurement becomes genuinely useful to you rather than just to us. A static pressure figure and a duct leakage result are evidence. “The back bedroom is hot” is a complaint; “the return is at 0.9 inches of water column and the bedroom register is delivering a third of the design airflow” is something a warranty department has to answer.
Two to ten years old
Any warranty route on the mechanical side has almost certainly closed, so this is now a question of what is worth spending. The good news is that the likely causes are still the cheap ones. Duct repair, sealing, adding a return, correcting airflow and cleaning a coil properly together cost a fraction of a system, and in houses of this age they are usually the whole answer.
Equipment this age is nowhere near the end of its life in this climate, so anybody proposing replacement should be able to show you why the existing system cannot be made to work. Ask for that in writing before you agree to anything.
You bought it from the first owner
Two things to check, and they are both worth a phone call before anything else. Some builder warranties transfer to a subsequent owner and some do not; it depends on the document and on how the sale was handled. Separately, manufacturer warranties on the equipment itself often run five or ten years on parts and frequently do transfer, sometimes only if the transfer was registered within a short window after the sale.
Neither is likely to cover a duct problem, but the compressor and the coil are exactly the parts where it would matter, and we have seen people pay for a part that was covered. Find the model and serial numbers on the outdoor unit and the air handler and start there.
The other thing a second owner is entitled to be suspicious about: whether anything was ever put right. If the first owner reported a hot bedroom and was told it was normal, you have inherited both the room and the story.
What to do next
Get an airflow measurement at the register and a look in the attic above that room. Do not let anybody talk about equipment until both have been done. If it turns out to be duct, the repair is usually an hour or two of work.
What to do next
Ask for three numbers: static pressure, duct leakage and the delivered airflow. Together they say whether the system is being starved or is genuinely at its limit. A replacement quote without those three numbers is a guess, however confident it sounds.
What to do next
Ask for the return side to be tested and sealed before anybody discusses equipment. And be sceptical of any proposal to go up a size — oversizing is the usual cause of this complaint and more of it will make the house worse, not better.
What to do next
Get a static pressure reading, and get the number. Not “it’s a bit high” — the figure, and what the manufacturer allows for that unit. If somebody has sold you a dense filter for a system that cannot carry it, that is a five-minute fix.
What to do next
Get a duct leakage test with a number attached, so you have a before and an after. Then check the filter, the registers and what the thermostat is actually doing, because in perhaps a third of these calls the answer is on that list and costs nothing.
What this page will not do
It will not tell you that your builder did something wrong. We have not seen your house, most of the causes above are ordinary consequences of building quickly, and a page on the internet is not a position to accuse anybody from. What it will do is tell you which measurements turn a complaint into a claim.
It will not give you a figure for anything. No price, no leakage percentage, no savings estimate. The whole argument here is that the numbers have to come from your house, and inventing them would undo it.
And we will tell you when the work is not ours. If the honest answer is that your builder should be doing this under warranty, we will say so, give you the measurements to attach, and let you go and use them.