Renovating your home can increase its resale value. But don't expect a dollar-for-dollar return. Some upgrades (an extra bathroom, for example) pay off; some (like swimming pools) don't pay off at all. If you want fine marble in the foyer, spend away. But don't count on buyers being willing to pay as much for it as you did.
Attic doors are a major source of heat loss in many homes. To stop airflow, weatherstrip the edges and insulate the back side of the attic door. Fold-down stairs can be covered with a lightweight box made of rigid insulation.