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The HVAC in a new house, stage by stage
A production builder installs a system that meets code and passes inspection. That is not the same as a system that was balanced, verified and set up for this altitude — and the window for asking about it closes quietly.
What this page is and is not
It is a list of questions worth asking and when to ask them. It is not a claim that your builder has done anything wrong — everything described here is legitimate to leave out, it is priced out of a production house on purpose, and the trades doing it are working to the contract they were given. It is also not legal or contractual advice. What your purchase agreement and your warranty actually cover is a question for you and your attorney.
Choosing options, about to sign
The best moment there isEverything below is cheaper now than it will ever be again, because it is a line on a contract rather than a change order or a retrofit. Two of the four cost nothing at all — they are questions, not upgrades.
Ask what sizing calculation was done
Equipment should be sized from a room-by-room heat loss and heat gain calculation for your plan, your elevation and your orientation — not from a square-footage rule of thumb applied across the whole community. A house with the sun on its west face is not the same house as the identical plan facing north.
Ask forA copy of the load calculation for your specific lot and elevation.Ask where the equipment and the ducts are going
Ducts in conditioned space perform far better than ducts in an unconditioned attic, and on a plan with a second floor this is decided long before anybody breaks ground. If there is an option to keep them inside the envelope, it is worth more than most of the finishes on the list.
Ask forWhether the trunk and branches run in conditioned space, and what the alternative is.Ask about zoning before the ductwork is designed
On a two-storey house, zoning designed in at this stage is a normal system. Zoning added afterwards is dampers cut into finished ductwork, a controller, a bypass and a compromise. If you already know the upstairs will need separate control, now is when it costs least.
Ask forWhat it costs as an option now, and what changes in the duct design if you take it.Ask whether commissioning is included
Balancing the airflow room by room, verifying the charge under real conditions, and setting gas pressure for the altitude. Usually it is not included, and asking makes it clear you intend to check.
Ask forWhether a balance report will be produced, and who gets a copy.Under construction
The one visit that matters is before drywallThe equipment selection and the duct routing are fixed by now, and zoning as a designed-in option has probably passed. Everything else below is still live, and the pre-drywall walkthrough is the single most valuable half hour of the whole build — after it, the ductwork is behind a wall for the life of the house.
Look at the flexible duct before it is covered
Flexible duct should be pulled taut and supported, with gentle bends. Sagging, kinked, compressed or excessively long runs are the commonest airflow problem in a new house, and they are visible and fixable right up until the drywall goes on.
Ask forA pre-drywall walkthrough where the mechanical work is specifically in scope.Count the returns
Look for a return in or near each bedroom, or a transfer path over the door. A house with one large central return and six bedroom doors that close is a house that will be uneven from the day it is handed over, and adding a return afterwards means opening ceilings.
Ask forWhere the return air comes from in each closed room.Check where the bathroom fans terminate
They should go outside, through a hood, not into the attic or the soffit. This is a recurring find in fast-built housing, it is invisible after handover, and in this climate it puts moisture straight into an attic every day.
Ask forConfirmation that every extract fan terminates outside the building envelope.Photograph everything
Ten minutes of photographs of open walls and ceilings is the most useful thing you will ever have. It settles arguments later, it tells any future contractor where things run, and it costs nothing.
Ask forNothing — just take the photographs yourself, room by room, before drywall.Moved in, first year
The warranty window is open — use itThe pre-drywall look is gone and the ductwork is now behind finished surfaces. That is genuinely a loss. But this is the stage where the most is still recoverable, because you are inside the builder’s warranty period and a documented complaint made now carries weight that the same complaint will not carry in eighteen months.
Live through one summer and one winter, and write it down
Which rooms are uncomfortable, in which season, at what time of day. A note per room over a year is worth more than any single visit, and it converts “the upstairs is hot” into something specific enough to act on.
Ask forNothing yet — but keep the list, dated, in writing.Get the airflow measured before the warranty runs out
Static pressure across the system and airflow at each register. If the numbers show the house was never balanced, that is a finding you can take to the builder while it still matters — and if it shows the system is fine, you have stopped worrying about it.
Ask forA balance report, from the builder if they will provide one, independently if they will not.Check the altitude set-up
At roughly 5,300 ft the input rating on the plate is a sea-level figure, and whether the appliance needed an orifice kit or a pressure change is in its own installation instructions. On a fast-built house this is worth verifying rather than assuming.
Ask forWhat was done for altitude on the model actually installed, and by whom.Raise anything mechanical in writing, before the anniversary
Phone calls are not a record. Anything you have noticed — a room, a noise, a smell when the heat first runs — goes in an email with a date on it, whether or not it has been fixed yet.
Ask forWritten acknowledgement of each item, with a reference.One to three years in
Now it is your house, and your decisionOn most builders’ terms the window for mechanical items has closed, and anything not raised in writing before it is now yours to fix. That changes the question rather than ending it — because the fixes are mostly cheap, they are permanent, and they are worth doing on a house you are keeping.
Measure first, buy nothing
Static pressure and register-by-register airflow. Almost every “this house has never been right” call we take in a newer house ends in a duct finding rather than an equipment finding, and equipment is the expensive answer to a cheap problem.
Ask forNumbers, on paper, before anybody quotes you a replacement.Add the return that was never there
The single most effective thing done to an uneven new house, and a fraction of the cost of any equipment. It fixes both seasons at once and it does not care how old the house is.
Ask forWhat it takes to add a return or a transfer path to the rooms that close.Seal the ducts you can reach
Accessible joints in a basement, a crawlspace or an attic. Cheap, undramatic, and it improves heating and cooling at the same time. In an attic in this climate it is the difference between a bedroom that copes in August and one that does not.
Ask forA price for sealing accessible ductwork, separately from anything else.Commission it now, late
Balance the airflow, verify the charge, confirm the altitude set-up, set the controls properly. It is exactly the work that was skipped at handover, it costs a fraction of replacement, and on a house you intend to keep it is the best money on this page.
Ask forA commissioning visit with the figures handed over afterwards.A bigger furnace is almost never the answer to an uneven house — it short-cycles, heats unevenly, and makes the cold room slightly worse. And nothing on this page requires you to open, adjust or inspect anything yourself beyond looking and photographing.
Five things worth having in writing
None of these is unusual to ask for and none of them costs anything to request. Having them is what separates a house you can argue about from one you cannot.
The load calculation
For your plan, your elevation and your orientation — not a community average.
The equipment model numbers
Outdoor unit, indoor coil and furnace or air handler, as a matched set. It is also how warranty registration works.
The balance report
Airflow measured room by room, with the figures. If none exists, that answer is itself worth having in writing.
What was done for altitude
On the model actually installed, according to its own installation instructions.
Your own pre-drywall photographs
The only item on this list that nobody can refuse you, and often the most useful.