If you are looking at a prewar house in Collingswood or Haddonfield, the answer to the duct question comes before the home inspection, not after. Check four things: how the ducts get to the second floor, whether there is a return up there or just one hallway grille, how the attic runs are hung and sealed, and what vents into the chimney. A normal walkthrough almost never shows any of it, because all four live above a dropped ceiling, inside a closet chase, or behind a hatch nobody opens during a showing.
Why the second floor is the part that changed
Local housing plans for Haddonfield and Collingswood date roughly half of Haddonfield's homes and nearly half of Collingswood's to before 1940, which means the heating system you are looking at today is almost never the one the house was built with. These houses started with gravity warm air, hot water radiators, or steam, none of which needed a duct system running to the second floor the way central air does now. When a later owner added central air or converted to forced warm air, the second-floor supply had to go somewhere the original framing never planned for: up through a closet, across an attic, or down inside an exterior wall that was never built as a chase. That retrofit is the part worth understanding before you buy, because its age and quality vary far more than the original structure does.
Trace the supply to the second floor
Ask how the upstairs rooms get their air and go look, even if it means opening a closet door or asking the listing agent for access to the attic hatch. A duct that runs through a proper chase, boxed in and insulated, is a different situation from flexible duct laid loose across attic joists or snaked through a stud bay with no chase at all. The second one works, but it is exposed to attic heat in summer and attic cold in winter, and it is the kind of run that gets crushed by whoever last stored boxes up there. If the supply to the second floor disappears into a wall with no visible chase and the plans show no obvious duct route, ask directly when that work was done and by whom, because that answer tells you more about what is behind the drywall than the seller's disclosure usually will.
Look for a return upstairs, not just a supply
Retrofits often add supply registers to every bedroom and stop there, leaving one return grille in the downstairs hallway to serve the whole house. Close the bedroom doors at night and that single return has nowhere to pull air from upstairs, so the system starts short-cycling and the second floor runs warmer in summer and colder in winter than the rest of the house. A return upstairs, even a small one, is worth asking about specifically, since its absence is common enough in these retrofits that it should not surprise anyone, but it is also a reasonable thing to plan a fix for as part of the purchase rather than discover after moving in.
What the attic run looks like up close
An attic hatch and a flashlight tell you more than most of the rest of the inspection combined. Look at how the flexible duct is hung: proper straps every few feet holding it level, or duct resting directly on insulation with dips where condensation and dust collect. Check the boots where each branch meets its register, since a loose boot in an attic run leaks conditioned air into the attic every time the system runs. If the runs look tired, crushed, disconnected, or undersized for the rooms they feed, that is Air Duct Repair territory, and it is worth getting a number on that work before the offer goes firm rather than after.
What vents into the chimney matters as much as the ducts
A prewar house in this area was often built with a masonry chimney serving more than one purpose: a fireplace flue and a furnace or water heater flue sharing the same stack, sometimes with the second flue added years after the first. When a furnace gets replaced with a newer, higher-efficiency model, its exhaust characteristics change, and an old flue sized for the original equipment does not always suit what is venting into it now. Ask what the furnace and water heater vent into, and if either one shares a chimney with a fireplace that gets used, have the flue looked at along with the ducts. The National Fire Protection Association's guidance on heating equipment points to venting and flue condition as a recurring factor in heating-related incidents, which is reason enough to have a chimney inspected rather than assumed sound because the house has stood for decades. Chimney Cleaning covers the inspection and clearing of the flue itself, and separate flue issues get flagged for repair rather than folded into a cleaning quote.
The attic air handler and the drain pan below it
Where central air was added to a prewar house with no basement space for an air handler, the unit sometimes ends up in the attic instead, sitting over a bedroom or hallway ceiling. That placement makes the condensate drain pan and its overflow switch worth checking directly, since a clogged primary drain with no working secondary protection is how a slow leak becomes a stained ceiling. Ask when that pan was last serviced and look at the ceiling below it for old water marks, even faint ones that were painted over.
What to ask the seller, and what to have checked before closing
A seller may not know the answers to all of this, and that is fine, it just means the questions move to the inspection. Ask when the duct system was added or last worked on, whether the second floor has ever run noticeably warmer or colder than downstairs, and whether the chimney has a liner or has been inspected recently. Then have someone trace the supply and return paths, open the attic hatch, and check what vents into the chimney before the deal is final. A walkthrough of the ductwork and flue produces a written estimate that separates what is cosmetic from what calls for Air Duct Repair or chimney work, and that document is worth more at the negotiating table than a guess made from the driveway.