Document the condition
Note location, timing, weather relationship, changes over time, and any previous work. Photos and simple measurements can improve the first conversation.
Read the local context
Window openings in Naperville-area homes reflect the era they were framed in: older homes near the historic district and early-20th-century additions often carry smaller, non-standard rough openings, while postwar ranch and split-level subdivisions standardized around wood double-hung sash that has since been replaced piecemeal over decades. DuPage County's building requirements and, for homes inside recognized historic areas, added review can affect what can be swapped in versus what needs a custom unit. Illinois' summer humidity and winter cold both put real demands on seal and frame performance regardless of a home's age.
Ask what will be hidden
Installation method, flashing, sill condition, frame material, glass package, trim restoration, and solar exposure matter as much as the unit itself. The written scope should explain the preparation and verification that will no longer be visible at completion.
Compare complete scopes
Look for protection, access, materials, permits, testing, cleanup, restoration, exclusions, warranties, and change-order rules.
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.