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
The City of Naperville is the local permitting authority for land-disturbing activity and requires property owners to maintain on-site stormwater control facilities; Naperville has adopted DuPage County's floodplain regulations for the portions of the city within DuPage County, and Naperville's own stormwater plan relies on storm sewers, detention basins, and overflow routes. DuPage County Stormwater Management enforces the countywide Stormwater & Floodplain Ordinance across five program areas -- Watershed Management, Floodplain Mapping, Water Quality, Regulatory Services, and Flood Operations -- and the county's building code requires soil testing in areas likely to have expansive clay soils.
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.