Window Replace vs Repair ROI

First, it combines window age with your draftiness and condensation ratings to estimate an overall “condition severity” score. Then it estimates (1) annual energy-loss impact from those symptoms and (2) how much repairing is likely to buy you based on the remaining lifespan you expect after repairs. Finally, it checks whether replacement payback looks realistic and whether you’re close enough to end-of-life to justify replacing now.

Draftiness and condensation are treated as proxies for performance issues, but they don’t tell the full story—installation quality, frame condition, and glazing type can change outcomes. If draftiness is high but the windows are young, the calculator will effectively push you toward checking for sealing/installation problems rather than assuming replacement is inevitable. If condensation is severe, it also increases the chance that replacement (or more than a simple repair) will be economically sensible—especially with high energy costs.

If you enter a very low window age but high draftiness/condensation, expect a recommendation leaning toward repair/reassess rather than full replacement—because the underlying issue may be fixable at the installation level. If your “expected remaining lifespan if repaired” is very short (under 5 years), the tool biases toward replacing now. If the inputs imply an unrealistic lifespan (for example, age that doesn’t align with remaining useful life), it triggers a warning so you can sanity-check your assumptions.

This is an indicator-based model, not a measured energy audit. It doesn’t use actual U-values, air-leak testing results, or local climate/orientation, and it treats replacement cost as a generalized average unless you provide a project estimate elsewhere in your workflow. It also doesn’t fully monetize comfort, noise reduction, or resale value—so if those are major priorities, use the recommendation as a starting point.