Last year on my tax form, I tried to enter and energy efficient window, as a repair for a rental property. It said that I had already used my lifetime credit (or something like that?) Is there a limit on what you can claim as an energy efficient home imp

[AmyC]

Yes, there are several rules.  Here are two sources of information:

The IRS: Energy Incentives for Individuals: Residential Property 

Turbo Tax plain English: Energy Tax Credit: Which Home Improvements Qualify