Interesting exterior insulation retrofit using waterjets and wet vac for precise trenching

A homeowner in an online building forum flagged a foundation insulation method they'd never seen before: using waterjets and a wet vacuum to cut a narrow, precise trench along the outside of a house foundation, rather than digging it out with an excavator. The idea is to expose the foundation wall from outside so insulation can be added without the mess and disruption of a full excavation.

The method comes from a video produced through the Department of Energy's Building America program, done with the University of Minnesota's NorthernSTAR research group. The homeowner who posted about it wondered whether spray foam is the only insulation option that works with this waterjet-and-trench approach, since the tight, narrow cut seems suited to sprayed-on material rather than rigid boards.

For someone thinking about insulating their own foundation from the outside, this is worth watching as an emerging technique rather than something widely available yet. Exterior foundation insulation is normally a disruptive project involving heavy digging equipment around your house. A precision trenching method that limits digging to a narrow slot could mean less landscaping damage and a faster job, but there is no information here yet on cost, availability, or which contractors might offer it. If exterior foundation insulation is on your radar, it may be worth asking around to see whether this kind of low-disturbance trenching has reached installers in your area.