Net-zero energy homes hold a lot of appeal, but they're often too costly for the average homeowner.

Now, a team in The Netherlands is working to change that through an innovative project aimed at turning old low-income housing into net-zero houses, thanks to a retrofit kit that installs in less than a week, reports Adele Peters for Fast Company.

Prefab parts include a roof solar panel array, new exterior facades, interior refurbishments, and an energy module installed in the backyard. The best part? The rehab comes at no cost to tenants or building owners:

A government team called Energiesprong realized that renters in the social housing projects were already paying a yearly energy bill of around $2,200. The retrofits eliminate that bill—and by asking tenants to pay the social housing corporations the same amount they would have paid a utility, it completely funds the construction process. Tenants don't pay any extra, but they end up with a fully renovated house.

While the system is particularly effective in The Netherlands due to its large stock of similar houses, developers state that the basic concept could work virtually anywhere and are planning to start exporting the system to the U.K. At the very least, the model presents an interesting challenge to builders' conceptions of what it takes to build net-zero homes.