A few years back I saw a photo blog of a home build where they installed what looked to be a huge polyethylene water tank, something like this. A guy climbed in the manhole and installed a big coil of copper tube, I think it was anchored with string.

The tank was placed in a small room not much bigger than the tank, just off the garage. After plumbing the connections, including a drain line out to the garage, they filled the entire room with blown cellulose.

I love the idea of growing my own heat in my back yard

Great when you are young and have kids at home, not so much when older<G> .

We heated over 5000 sq ft with wood for over 30 years. When DW hit 55 (closer to 2 decades ago than one!) she said she was tired of hauling wood when I was gone on business trips. This was after the kids were grown, we use to pay them 50 cents to start the fire when they got home from high school.

Anyway, GSHP and air-air now, but actually have a big fire today as it is supposed to get to the teens tonight.

Have never paid for wood, used to burn close to 10 cords per year. Water wall fireplace with circulating water.

Anyway, just keeping the fire going yesterday seemed like a chore, hard to recall we did it as a matter of course for so many years.

However, say 35 years, average of abut $1000 utility cost not spent, say about $60K-$70K not spent and grown made it worth it.

Thinking that way, having our own well and septic ($80 mo here for water and sewer) was another $50K saved/invested!!!

5000 sq ft... isn't that about the size of a bowling ally?

-AC