Simon & Jessica Miller on Instagram: "A lot of people come to us thinking dual-fuel is the simpler, more flexible upgrade. And it can be... in the right home. But here’s the part almost no one knows: there are multiple layout and venting scenarios that can make dual-fuel more complicated than it looks. The chimney-share issue is just one of them. If your furnace and hot water tank share a chimney, switching to a high-efficiency furnace means that chimney can’t be used anymore. It needs its own v