There are plenty of benefits to investing in replacement windows, including:

When is wind power right for you?
Five tips for an eco-friendlier yard
A home energy audit checklist
The Benefits of LEED-Certifying Your Home
An Introduction to Energy-Efficient Appliances
IECC Compliance Guide For Homes in the District of Columbia
NEW HOMES: Selecting Energy Efficient Windows in Delaware
Winter Energy Saving Tips
IECC Compliance Guide For Homes Missouri
The Tax Credit for Installing Energy Efficient Windows, Doors and Skylights
Green Building Ideas
Energy Conservation and Indoor Air Quality: Lessons From the Past Have Relevance for the Future
IAQ and Children's Health - Protecting Children's Health
Mold
Indoor Air Quality (IAQ)
Federal Solar Tax Credits: Residential FAQs
Green Building Program: Many Incentives for Building Green in Anaheim
The Benefits of Residential Solar Power
Planning for PV: The Value and Cost of Solar Electricity
Solar Leasing for Residential Photovoltaic Systems