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Posts: 2
Reply with quote  #1 
Hi, new member here. First post. 

Here is my plan. I have put much thought and a fair amount of research into this. That means that I know enough to get started but am dumb enough to not know how much I don't know. I would appreciate any input.

I am building a barn 36' x 64' with 16' tall walls. Under the floor there will be a block cistern, insulated and sealed 12' x 5-6 x 4' deep, about 1800 gal.

I would like to heat the barn with in floor radiant heat as well as heat the house (2400 sq ft) utilizing the heat pump blower. The heat pump does not work, only the electric backup heat strips. I plan to have installed a heat exchanger in the plenum to distribute the heat.

I have a 16' x 64' south facing wall on which to build solar thermal panels so surely that would be enough to heat the water. I will utilize hot air collectors in the barn. I plan to also have a wood stove to heat the air in the barn as well as the water after a stretch of cloudy days, but hope to use mostly solar heating.

I am thinking to fill the cistern with water. Use a close loop system filled with RV antifreeze in the collectors, and a separate closed loop system to transfer heat into the house and barn floor; mostly because if I were to ever get an outdoor wood boiler, that requires a closed system.

For heat exchangers in the cistern I plan to use large truck radiators hooked in series. For the collector (heat in)side i would mount them lower in the water. For the heat out side I would mount them higher in the water to take advantage of stratification. For the wood stove I would take the water from the bottom on one side and empty it into the opposite corner on the bottom other side.

Now for the summer. I think I would like to run pipes underground to cool the water in the cistern to try to cool the air in the house. I have to move dirt anyway. We have a window AC unit that works to a certain degree, at least the Wife is happy with it. If we can use the central blower to cool the air at least some, surely that would help. I could also install radiators with fans in the barn to help cool the shop.Sort of like a poor mans geothermal.  I realize that I can't cool the concrete floor. 

I have looked at the Chiltrix system but it seems expensive to purchase. I may eventually install a new heat pump in the house.

Now for my questions:

1. does this sound like it will work?

2. Should I double the size of the cistern? easy to do before the floor is poured.

3. What do I do with the solar collectors in the summer? I don't want heat. Take the glazing off? cover them?

4. Are truck radiators a decent choice for exchangers? or are commercial one that much better? I live 1 mile from a junkyard.

5. Has anyone ever tried to cool the air in this manner? I saw a news story on you tube about a guy in Nebraska that raises citrus fruit in his solar and geothermal greenhouse. He pipes air underground to heat to 52 degrees at night in the winter with solar to heat in the daytime.

I know I have much to learn and would appreciate any advice that I can get.
Thank you,


Posts: 1
Reply with quote  #2 
Hi PAWood,

I'm also a new member, but I have 30 years of construction / design experience.

All of your ideas have great ingenuity. I would recommend separating the systems for the house and barn. The requirements for a typical house and an open barn are completely different and it would be difficult to balance the system. The water temperature required is completely different. Both sides would be compromised.

The ideas in the barn should work well, especially the radiant heat for such a tall space. You wouldn't need the radiators as heat exchangers or a larger cistern if the barn is the only area being tempered. I would be concerned about using a block cistern under a concrete slab though. I realized that you're looking for DYI solutions, but a plastic tank isn't too expensive and would eliminate any risk of leaks for decades. As a money saving idea, sand is a great insulator.

The radiators are engineered as liquid to air heat transfer and would not work as liquid to liquid, but they would work well for your cooling idea. Basically it would be a typical fan coil system as used in commercial high rises. However, depending on the size of the cistern, you could lose cooling capacity.

I hesitate to throw a new idea at you, but it sounds like you might have enough land (?) to consider geothermal for the house. You talked about running pipes underground. That would give you heating and cooling using the existing ducts. A horizontal field will work fine although a vertical well is better. If there is a pond nearby, that's the best and will eliminate most of the digging.

A little wordy here, but good luck and let us know how everything turns out.


Posts: 2
Reply with quote  #3 
Thank you for the response!

I did wonder about the water temp for both systems. The temp for the house via a water to air exchanger in the plenum can be 185 degrees F but the radiant floor would have to be balanced I guess with return water to maybe 100 degrees?  I don't think  the floor should be overly hot. 

The block cistern is already in place, but can be made larger. The block cores are filled with concrete and will be coated with a waterproofing masonry coating.  I plan to either insulate it with 2-3" foam board and seal it with rubber OR have it sprayed with closed cell foam. 

I suppose that instead of radiators I would just use copper of PEX coils.

My main concern is heating a small portion of the barn, then the house and whatever is left over can heat the majority of the barn. when I am working in the barn the wood stove can be used which will heat the air and the water. 

A geothermal system is expensive to install. I would love to have a pond, have the perfect location for one and have dreamed of it for decades. For my ground to hold water would take a miracle and a lot of money. My ground does not hold water and any pond would have to be lined with rubber or bring in bentonite clay from somewhere else.

I have to move dirt anyway, hence the idea of burying pipes to cool the water for the cistern for cooling. I wonder if water from those pipes could be used to balance the temperature in the radiant floor heat when the cistern temp is much higher?

Still thinking.

Rick H Parker

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Posts: 809
Reply with quote  #4 
How far down is your summer water table?  A buddy of mine bought some land with a old 30 ft hand dug well on it. The water was not potable but there was enough flow that it could be used as a heat sink.
Rick H Parker
Kansas, USA
Electronics Engineering Technologist
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