You probably heard about my noisy furnace (Rheem Criterion II, 100K BTU, 4 burner, with a 3 ton Carrier AC) that vent through the wall between 2 bedrooms. It was throttling for about 1 min every 15 mins because it is over powered, waking people up at night, and drying the air when it is on. I've replaced the exhaust draft fan and it helped the noise problem a lot (probably at least 10-20 dB), but it is still a bit noisy and it is still very dry. So, I'm thinking about replacing it to quiet down and make it more comfortable. I'll never make the money back in terms of efficiency, but at least I can sleep better. Here are the 2 approaches I can think of: 1) A new 90%+ that vent to the side of the house, the new exhaust would be the expensive part, the furnace is probably going to be just a cheap 40k BTU 1200CFM dual stage Goodman. I won't be able to do anything and will like hire a pro. I'm guessing it would be a $4k-5k job consider how expensive labor is here. 2) A new 80% 40K BTU 1200CFM dual stage Goodman. I might be able to swap it out myself but I do need to make an adapter (i.e. cabinet width going from 19" to 14") between the furnace and the existing inlet and outlet. I should be able to just dip switch my way to hard wire it to 32K BTU and max airflow. The exhaust draft motor is still blowing through between the wall, so there'll still be noise, but the 66% reduction in heat will likely make it more comfortable and throttle a lot less. If exhaust vent muffler exist, I'd like to install one before it reaches the bedroom. So far I see a lot of these thing on pot growing hobby site but I'm wondering if there are furnace specific muffler instead. The furnace, adapter, and exhaust will likely cost $1k for parts, and I might be able to install them myself. Suggestion?