Many utilities offer incentives to homeowners who make improvements that save energy. Contact your utility company to determine if you're eligible for a low-interest loan or discount for replacing your windows and doors. Ask about energy-efficient insulating features such as argon gas between the panes of glass and a Low-E coating.
If your home renovation requires new walls, you may want to consider using metal studs. They have many advantages in a basement area, where moisture and insects can be a problem. Metal studs are easy to assemble, and you can pre-cut several at once with a carborundum blade on a power saw. Then, they quickly fasten together with self tapping-screws. Metal studs are lightweight, fireproof, and recyclable.