Retrofit Strategies & Sequencing11 / 13
Window & Door Replacement
Payback for single to double/triple conversion; cost per m²; bundling with other work.
10 min read · Jacob Willis, Net Zero Lead · Last reviewed July 2026
Replacing windows is the most visible fabric upgrade and often the one occupants ask for first. On pure energy grounds, though, it usually has the longest payback of any fabric measure, because windows are a small fraction of the total fabric area. Knowing when replacement genuinely makes sense, and when the money is better spent elsewhere first, avoids both disappointment and wasted capital. This lesson works the energy case honestly, then sets it alongside the comfort, condensation and noise benefits that usually justify the decision.
In this lesson
- 01The energy case, honestly
- 02The wider case
- 03Whole-window and installation matter
- 04Sources and further reading