3 years with Accoya siding in coastal Maine. Hard data on how it's actually performing.

Installed Accoya siding on our house in midcoast Maine in 2022. 1,800 sf, horizontal lap profile, Teknos paint system (2 coat). House is 400 ft from the ocean, full northeast exposure. Here's my 3-year report: Dimensional movement: Measured 6 sample boards seasonally with calipers. Maximum width change across all seasons: 0.8mm on a 140mm board. That's 0.57%, compared to cedar which typically moves 3-4% seasonally. This is why the paint is still perfectly bonded, the substrate isn't moving underneath it. Rot/decay: Zero. Anywhere. Including bottom course which is 8 inches above grade. Checked with a moisture meter and a pick test, rock solid. Paint adhesion: Still at 100% after 3 Maine winters. Zero peeling, zero cracking, zero chalking. The Accoya manufacturer claims 2x paint life and so far that checks out. Issues: One board developed a small split at a nail hole, I think this was a fastener issue (ring shank nail, should have pre-drilled). Fixed with epoxy and touch-up paint. That's literally the only maintenance in 3 years. Cost: Paid for the material. Expensive, yes. But my neighbor's cedar siding (installed same year) already needs full repaint at year 3. Mine won't need it until year 8-10 minimum based on current trajectory. One limitation: Max length available is about 15'9" (4.8m) due to the acetylation reactor size. If you need 20' boards, you're looking at tropical hardwoods, sapele or ipe from someone like my supplier who stocks long lengths. But for most residential, 16' max is fine.