Are you wanting to do a complete tear out of the existing windows and replace with wood frame double insulated? If not a sash replacement using the existing frames will be a lot cheaper and a reasonable substitution. I've used the Marvin brand for wood sashes and an Anderson vinyl line called "Silver" that also works well. I can install about 3 a day which comes out to about $80/window labor.
I'm looking for vinyl mostly double hung but a few sliding windows. . I am looking to replace existing windows that were put in 15 years ago when the house was built. They are wood with some getting fairly rotted.
Marvin is very well reviewed on consumer reports. Anderson is the window I have seen the most especially growing up in NJ where it seemed that's all was ever put in.
