We installed new windows in 2008 ($7100) and did not take a deduction (I don't remember it being an option). Can we take a deduction for them in 2019
You can't claim a deduction or credit in 2019 for something you purchased in 2018.
However, you can amend your 2018 return to claim residential energy credits if your windows qualify.
Please see this TurboTax website: How do I amend my 2018 taxes to claim energy credits?