I've been using CoreTemp for over 10 years now, I think. Owner Richard and his trusty partner Erik have taken good care of my older furnace. A few years ago, they installed a Rinnai tankless water heater for me. They also just replaced my old furnace with a new high-efficiency model, as well as installing a new humidifier and air conditioner. (It was my request that they do all that work at the same time, since it would be more efficient. Richard does *not* push to up-sell people.) They work quickly, carefully, and they clean up after themselves beautifully. And, it being COVID-19 times, they used their masks and kept distance at all times. Richard also sterilized the bathroom, the staircase banister, and all door handles they touched on his way out - excellent attention to detail.
Over the years, and as others have said, Richard has always been there when you need him. In my case, over the years, he has helped with heating failures after hours by FaceTime, he has followed up on the furnace situation when he was on holiday, and he has even arranged for substitute service people when he was out of the country. Richard is honest, he clearly cares about and takes pride in what he does, he makes sure you are educated about your choices, and he does not waste your money. You can't ask for more in a tradesperson. I recommend CoreTemp without reservation.