Every winky-dinky house consultant will try to impress you with a thermal camera.
Now that thermal cameras come with phones, we can all do it, and find that's it's useless. Nearly all heat loss trouble comes from air leakage inward. Then it goes out the chimney. Putting more insulation in the roof doesn't do much. I got the first big improvement from replacing the upper windows and the front door. Get casements only, no sliders. Casements and the magnetic door seal like a fridge.
Then the next big improvement, back door and basement windows hardly made any difference. The physics probably involves the cold air directly hitting the floor and going to the furnace. I also leave some ventilation for the furnace. If all is good, then you never need a humidifier, normal showers and dishwashing is enough.
Save your money, go directly for a window change. Physics rules!