Document the condition
Write down where it happens, when it started, how weather seems to affect it, and what has already been tried—a couple of photos make the first call more productive.
Read the local context
Naperville's housing stock spans a wide range of eras, from the brick core near the original 1831 settlement through the ranch and split-level subdivisions of the postwar decades to large newer-construction homes on the city's edges, and each era carries different duct routing, insulation levels, and electrical capacity. Illinois' climate swings from humid summer heat to sustained winter cold, so equipment sized for one era's envelope often struggles in either direction. DuPage County's permitting process for mechanical work adds another planning step that varies with a home's age and prior renovation history.
Ask what will be hidden
The equipment is only part of it—duct leakage, insulation, and available electrical capacity all belong in the conversation, and the scope should explain how that hidden work gets checked once it is closed up.
Compare complete scopes
Compare every quote against the same checklist: protection, access, materials, permits, testing, and what counts as a change order.
What official local sources add
Climate is the real subject here rather than the stormwater ordinance. Northern Illinois asks a system to cover a genuinely wide range — deep winter design temperatures at one end and humid summers at the other — which makes the heat-pump balance point a real engineering question rather than a marketing one, and makes latent capacity matter as much as sensible capacity in July. The one place the city's framework touches this trade is condensate: a cooling system produces water, and a line discharging beside the foundation creates exactly the moisture problem the on-site stormwater control requirement exists to prevent.
Sources were reviewed 2026-07-26. Confirm parcel-specific flood zones, historic-district status, permits, and current requirements with the relevant authority before authorizing work.