With all of the vacant office space — 14.7 percent in Phoenix in Q3 — it’s tempting to want to convert it to housing. But it’s easier said than done. Case in point: One Camelback, where the owners defaulted on the loan this year when the project was 85 percent finished. Experts say the building has to be ripe for renovation in certain ways and situated in the right place. It’s also more difficult than it seems to adapt all the building systems from office to residential. However, re-using a building rather than razing it is more eco-friendly.