Great lakes Window

http://www.greatlakeswindow.com

United window and door

http://www.unitedwindowmfg.com/

National Vinyl

http://www.nvpwindows.com/

NFRC – National Fenestration rating council

http://www.nfrc.org/

NARI – National Association of Remodeling Industry

http://www.nari.org/

BBB – better business bureau accredited

http://www.bbb.org/central-western-massachusetts/business-reviews/windows-installation-and-service/omai-in-pittsfield-ma-201275

Angies List reviewable

http://www.angieslist.com/