How to Vet a Window Installer
AAMA InstallationMasters certification, references, and the questions to ask.
Window installation is roughly 50% of long-term performance. A premium window installed poorly leaks; a midrange window installed correctly performs beautifully for decades. Vetting the installer matters more than vetting the product brand.
Credentials to verify
AAMA InstallationMasters certification: industry-standard training program for window installers. Few national chain installers have it; many local pros do.
State contractor's license, general liability ($1M+), and workers comp.
Manufacturer authorized installer status for the brand you're buying. Andersen, Marvin, and Pella all run authorized installer programs that extend warranty coverage when used.
Questions that filter out the wrong vendors
'Do you use sill pan flashing?' (Should be yes, always — critical leak prevention.) 'Insert install or full-frame?' (Should have a recommendation based on your existing condition, not a default for all jobs.) 'What insulation do you use around the window?' (Should be low-expansion spray foam — high-expansion warps frames.)
Avoid same-day signing pressure from national chains. The real best installers expect you to compare and sleep on the decision.