The house comes before the product
How the unit gets installed, the flashing detail, the condition of the existing sill, the frame material, the glass package, trim rework, and how much sun that wall takes on all carry as much weight as the window itself.
Build a complete scope
- What is installed now, and whether original sash is worth repairing
- Whether paint layers on older openings change how the work may proceed
- Openings measured one at a time rather than assumed standard
- Frame material and thermal break, plus how the opening is air sealed
- Interior and exterior trim restoration, disposal, and warranty
Birmingham context
Birmingham's two dominant housing eras want different things. The long postwar run through the 1950s, 60s and 70s that built out Vestavia Hills, Mountain Brook, Homewood and the rest produced streets whose original windows were installed within a few years of each other and are now aging out together -- typically single-glazed aluminum, where the frame rather than the glass is the thermal weak point because aluminum conducts heat straight through the wall. The dense in-town neighborhoods and mill villages are the older case, where original wood sash is frequently repairable and openings are rarely standard sizes, and paint layers in housing of that age may be lead-bearing. Alabama's climate should drive the specification, and it inverts northern advice: controlling solar heat gain and air-sealing the installation matter more than insulating value alone.