If you heat with open fireplaces, then you can't seal the house unless you have really really good artificial ventilation (which you don't because it's 1840 still when you're building this house), regardless of how the house is built. A sealed house with a fire burning in it is a suicide machine.

> A sealed house with a fire burning in it is a suicide machine.

Modern designs use direct vent systems, where instead of using inside air for combustion, they bring in outside air (and then exhaust externally as usual):

* https://www.efireplacestore.com/five-things-about-direct-ven...

The warming of the house occurs via radiant heat and through any conduction of heat via the actual material of fireplace or stove.

That's not an open fireplace, though?