“This study compares the life-cycle costs of two residential window systems in a pre-1940 house in Boston, Massachusetts. One is an original double-hung window with a new triple-track storm unit. The other is a new, vinyl, double-hung replacement window. Our results are obtained from an algorithm that yields the total present value of all costs associated with a window system over its entire life, including acquisition, installation, maintenance, and energy.
Our study provided 2 notable findings:
the thermal performances of the two-window systems are similar; and
taking all costs into account, it is more cost effective to add a storm window to a historical window, and it remains so at all times for the full 100-year life we considered.”