Answers

The glass package and the insulation of the window are the most important. The best window would be quadriple or triple pane window with foamfilled sashes and krypton or argon gas inbetween the glass. The dense gas keeps the cold air out in the winter and the hot air out in the summer. The foam filled sashes keep the insulation like your walls. Also choose vinyl over wood for better insulation, 

Fiberglass windows would be a great option for energy efficency. We sell the Infinity by Marvin windows which are amazing!

Hi Pamela,

There are many great door & window product lines to choose from.  The most important consideration is the glass package and style.  I recommend consulting with a few glass companies and door/window contractors to help with the decision.  You need to choose your doors and windows based on location - cliamate zone.  Marvin is top of the line, but it is extremely expensive, just like Renewal by Andersen.  I recommend looking at Milgard, Jeld-Win and Andersen (not Renewal).  Good Luck! 

Gregg

Murray Lampert Design, Build, Remodel

www.murraylampert.com

Windows that have a .28 u factor or. Slightly lower, if installed correctly sealing the perimeter with foam are generally adequate for most homes. They will have low -e and argon normally in the csvity between the insulated glass. Now if you want to go for triple glazed glass and low e and Krypton glass, you can get down to .17 u. Generally the additional cost and added weight do not pay for the added expense. You may do well to also add insulation in the attic and make sure you ventilate the soffit and fascia. Heat tends to travel up. Make sure you get a good installer that know s how to insulate and do a quality install. 

the most important thing you need to make sure you have is a highly rated low-e window. low -e will reflect the solar rays away from the inside of your home so it doesn't heat up during the summer or direct sun etc and during the winter it works in the opposite manor. winter it will keep the heat inside your home keeping your house comfortable. there are many good brands of windows like Andersen, Western, Hurd, Marvin, Eagle (andersen), just to make a few. be sure and do plenty of research and get estimates from. 4-5 companies and compare dont just get estimates from 1 or 2 companies. good luck. 

Like Jim said before, a proper attic insulation will help with lowering your electric bill as well as heat reflective roof shingles and exterior paint, ex. tex-cote. For windows we use Anlin, 100% american made using the newest heat reflective technology. GreenLiving specializes in exterior energy efficient home improvements!

Pamela, there are a lot of window replacement options on the market. It's important to have a window which is designed for your region in the U.S. here is a chart by energy star which contains this info: https://www.energystar.gov/products/building_products/residential_windows_doors_and_skylights/key_product_criteria

If one is in your area, see if a local business manufactures windows tailored for your portion of the U.S. Avoid builder grade replacements, and try to work with companies which have been in business for 30+ years who can stand behind the warranties they provide. Always read the fine print, and make sure a remodeler will warranty the installation.