My brother rents houses and recently purchased a home with a fireplace insert, He described to me a copper coil that ran through the fireplace insert and then ran along the baseboards throughout the house. The copper line was hooked to a water source, passed through the coil, and distributed radiant heat thoughout the home with the heated water. I didn't get a chance to look at the system and, accordingly, my brother's discription was limited to "It was cool," I like this idea better then cutting into my existing ventilation trying to force heat through the stock furnace. Is this something you've seen? Will this heat sufficiently in a typical midwest winter? And just how would this be done without it looking like a Flux Capacitor from Back to the Future movie? Thank you! Note: I do have an InstaHot installed that heats all water throughout the home. Considered the same ideal but taping into the hot water line to heat the copper baseboard line. Drawback - Cost. The lights already dim when i turn the hot water on, can't imagine the cost of runing it continuously to heat the home. Thoughts? Thanks again!!

You never want to mix potable water and hydronic heat. As a stand-alone system it would not be a good idea. There would be no way to control the water temperature, and keep it from flashing to steam. Unless you had a way to marry the control for the pellet stove with the water temp. But how much do you want to spend jury-rigging?

i have no idea how many BTU the stove puts out but you need anywhere fron 80,000 to 140,000 to heat a home on a cold day.
most of the heat made by your stove heats the house by radiation.
if you can get an idea of how many BTU your stove produces you will have somewhere to start guessing.

Your lights dim when your electric hot water heater "kicks in" is a issue you want to resolve before considering a hot water heating system.

Best Wishes