Still, the perennial chart toppers for ROI are the cheapest to pull off. This year (as last), the No.1 finisher was installing loose-fill fiberglass insulation in the attic. Not exactly sexy, but boy, is it cost-effective! In fact, this is the only project that regularly pays back more than you invest, with an average 107.7% ROI.

https://www.realtor.com/news/trends/best-and-worst-renovations-to-make-in-2017/