Solar radiant heat project begins

[jim_wilson]

Well, if you are correct and rooms need "zones" and there "own loops" it was all for nothing because I didn't do that.
I heated the entire basement and was hoping that the basement transfers the warmth to the entire home.
The basement has separate zones but those separate zones on the floor below won't transmit to "zones" on the main floor. I can always add tubing under the main floor in the floor joists but I'm gonna give it a year with just a hot basement first. I sure hope this was not all for nothing.

Keep in mind also that my outdoor wood boiler is 500,000 btu's designed to heat 10,000 sq ft. The indoor backup boiler is 300,000 BTU's.

Hope it works this way!

The basement in my (old) house is unheated - uninsulated - and only stays some semblance of warm because the boiler is down there - and the washer and dryer are down there and because it's underground, and under the house. But it can get very cold down there. This means the floors in my house get very cold - and since I have what amounts to radiant heat in the house (cast iron "Baseray" baseboards) - the heat in the house works overtime I'm sure to warm all of that up.

Heat rises.

So.... theoretically speaking - heating the basement floor , which will be a large heat mass - will help to heat the rest of the house. I think the real question is in what the technical details are.

Did you insulate the floor between the basement and the first floor ? THAT would be mistake if you're looking for heating effect from that basement floor slab in the house. Are the foundation walls insulated *to the ground* - so that you don't get heat loss out to the earth. Was there insulation put in between the basement floor and the foundation walls to try and isolate the floor somewhat from those walls? Are you planning on insulating the inside of the basement walls - maybe with something to reflect the heat from the basement floor?

Depending on how you plumb up the rest of the house for heating - and how tall your basement ceiling is..... you always have an "out". If it turns out that the just heating the basement floor idea is not transferring enough heat to the rest of the house - you could always put down another layer of tubes over the existing floor - pour another 4-6 inches of concrete over the existing floor - and have that upper layer of tubes run thru to collect the heat from the floor and pipe it into the house itself - while the lower layer of tubes act as a way to transfer heat from the wood boiler into the slab and the ground. The whole floor would turn into your heat storage. You could probably also do the same thing with some creative plumbing and without the extra concrete pour. I'm just rattling off ideas. It's always good to know something can be "fixed" if the initial plan doesn't work out.

 

[lt190b]

To all interested. Lots of information on these subjects at EcoRenovator. lt190b

 

[Zick]

With current rebates through our coop and 30% tax credits, geothermal is really not much more expensive than a good high efficiency gas system around here. If you don't mind me asking, do you know what the additional was for the radiant heat in your house? 3k? 5k?

Your house is going to be beautiful by the way!

Radiant in the home was about 4k. Geothermal was about 17k. The rebates were not enough to make a difference. Look closely at geothermal before you shell out the cash.

When we built our house in 09', we compared a high eff boiler vs GSHP. As it turned out, the Geo was only slightly over 30% more than the boiler and w/ the 30% rebate it was an easy decision.

 

[IXLR8]

John,
I am starting to design a radiant heat system in my new house, I am going to steal some of your ideas but I have 2 questions;
What are you using for storage tanks and where are they located?
Did you consider using Solar PV panels and heating the water with an electric heater in the winter, then selling the excess electricity back to the grid in the summer? This is the direction solar companies here are starting to go with the price reduction of the panels and the converters.

 

[rmorey]

Well, if you are correct and rooms need "zones" and there "own loops" it was all for nothing because I didn't do that.
I heated the entire basement and was hoping that the basement transfers the warmth to the entire home.
The basement has separate zones but those separate zones on the floor below won't transmit to "zones" on the main floor. I can always add tubing under the main floor in the floor joists but I'm gonna give it a year with just a hot basement first. I sure hope this was not all for nothing.

Keep in mind also that my outdoor wood boiler is 500,000 btu's designed to heat 10,000 sq ft. The indoor backup boiler is 300,000 BTU's.

Hope it works this way!

It wont be for nothing. We put three loops in our basement and three loops in my workshop, run off seperate manifolds. The heatloss calculations suggested we had a 18,500 btu/hr loss in the house and a 22,000 btu/hr loss in the workshop.

We installed a 120,000 indoor wood boiler with a main loop connecting both manifolds to the boiler. The run to the house from the workshop is 80 ft. We only put heat in our basement, not on the main floor. The basement floor has a mixing valve feeding it, set to 130 degrees. Our upstairs maintains a constant 62 degrees, even at -15 degrees outside. We put in a small woodstove which we fire in the evening while watching tv. You will be fine.

 

[cartod]

It wont be for nothing. We put three loops in our basement and three loops in my workshop, run off seperate manifolds. The heatloss calculations suggested we had a 18,500 btu/hr loss in the house and a 22,000 btu/hr loss in the workshop.

We installed a 120,000 indoor wood boiler with a main loop connecting both manifolds to the boiler. The run to the house from the workshop is 80 ft. We only put heat in our basement, not on the main floor. The basement floor has a mixing valve feeding it, set to 130 degrees. Our upstairs maintains a constant 62 degrees, even at -15 degrees outside. We put in a small woodstove which we fire in the evening while watching tv. You will be fine.

great to know! You said to maintain 62 in home you have 130 degrees set at the valve. Is that maxed out? What temp does the basement stay at?

 

[muddstopper]

John,
I am starting to design a radiant heat system in my new house, I am going to steal some of your ideas but I have 2 questions;
What are you using for storage tanks and where are they located?
Did you consider using Solar PV panels and heating the water with an electric heater in the winter, then selling the excess electricity back to the grid in the summer? This is the direction solar companies here are starting to go with the price reduction of the panels and the converters.

I have been following this thread with considerable interest since I plan on building my retirement home in the next few years. As for selling excess electricity back to the power company, this isnt as easy as it sounds. The last few years, a company has been leasing land and building solar farms to sell power back to the power companies. At first, it was a pretty good business, plus the power company was giving all kinds of rebates so more people would get into the whole solar party. I recently checked on doing something similar, just not on such a large scale. I only want to produce for my needs. It seems now since so many solar farms popped up, the TVA, Our main source of electricity, has now stopped the rebate/credits and put in place a lot of restrictions to the type of system you can install, as well as to how much electricity you are allowed to produce. Of course, I can see the need to make sure your personal install meets the required safety concerns as well as capablity of matching the power they produce. I can not see how or why they think it necessary to limit the amount of power you can produce. Now it seems, if your intentions are to produce your own power, whether solar, hydro, wind or other means, and connect to the grid, then TVA has to be involved in the design of your home as well as the design of your power system. They will buy any excess power you generate, but they dont pay cash for it. Instead they just give you credit on your power bill and any excess power is banked in the event somewhere down the road, you dont happen to generate as much power as you used that month. Their explanation to me for these changes is that all those solar farms are causing a loss of revenue for the TVA and they can no longer subsidise any new solar installs. Personally, I dont think anybody has a right to tell me what i can do on my own property, so my intentions are to proceed as planned with my electrical production facility. I will connect to the grid, but i wont be selling any power to the local power company. I will just use a disconnect to seperate my house from the grid and only flip the switch in the event my power production doesnt happen to mean my immediant needs.

 

[IXLR8]

.... I will connect to the grid, but i wont be selling any power to the local power company. I will just use a disconnect to separate my house from the grid and only flip the switch in the event my power production doesn't happen to mean my immediate needs.

The power company in my area also credits one for power and doesn't pay $$ for it, but so far there are no restrictions. This is good to know as I am thinking of retiring to central NC and it will factor into my planning. Will your inverters work if they are not tied to the grid? Most grid tied systems will not work without the gird to sync the AC to, no grid to sync to... no output.

 

[rmorey]

great to know! You said to maintain 62 in home you have 130 degrees set at the valve. Is that maxed out? What temp does the basement stay at?

I should explain, the mixing valve comes preset to 130 (changeable if required). The boiler output is 170 degrees which is too hot for the floor. The pump is controlled by a thermostat on the wall, set to 70F/20C. When the air temp drops below 20C, the pump starts pushing 130 degree water through the floor until the air temp increases, causing the thermostat to shut off the pump. Remember, 130 is just a little hotter than your body temp (98.6) so it feels warm but not hot. Seems to run about an hour then shut down for about 6 hours. Hope that helps.

Sorry John, didnt mean to hijack your thread.

 

[Raspy]

John,
I am starting to design a radiant heat system in my new house, I am going to steal some of your ideas but I have 2 questions;
What are you using for storage tanks and where are they located?
Did you consider using Solar PV panels and heating the water with an electric heater in the winter, then selling the excess electricity back to the grid in the summer? This is the direction solar companies here are starting to go with the price reduction of the panels and the converters.

Jim,

I currently don't have storage tanks and am putting all the energy directly into the slab with a heat exchanger in the solar loop. I have a 30 gallon water heater that is the solar holding tank to allow the collectors to drain down. It's a closed loop. The water heater was poured full from a hose and capped, with the panels full of air. A pump is connected to the water heater drain and pushes water through the heat exchanger and up to the collectors, feeding from the bottom up. During that process the air in the collectors comes down the return line and into the tank. As the pump runs the warmed water from the collectors pushes the air ahead of it and enters the tank at the "hot" port. Water pours down through the air in the tank and goes out the drain line to repeat the cycle. The air is trapped in the tank. It cannot go back up the return pipe and it cannot go out the bottom because there is just enough water in the tank to prevent it. Then, when the pump shuts off, the water rushes backward down the supply line through the pump and into the tank through the drain line, refilling the tank. The air rushes up the collector return line and fills the collectors. This is the freeze protection system. No water in the collectors unless the pump is running and all done in a closed loop with no venting to the outside.

The feed to the collectors goes through a heat exchanger on the way to the collectors. The other path through the heat exchanger is in the floor circulation loop. It is always running (for now), so any solar energy is exchanged to the floor loop and heats the house.

Eventually I will have a bank of 120 gallon storage tanks. I'm planning four of those. They will always be assisting the domestic hot water by some percentage, and when no radiant is needed in the summer, will supply all the hot water. When the radiant is working, the floor will be brought up to a threshold temperature and then the balance of the energy will be stored in the tanks for the morning blast of heat before my feet hit the floor.

There are three categories of floor temperature. These are "cold", "invisible", and "warm". Cold is cold and is not desirable, but good for energy conservation in unused rooms. Invisible is between the shock of cold and the greeting of warm. The room is comfortable and stepping on the floor does not attract your attention. The floor is probably about 70 degrees. This temp is not noticed and can be used as a storage goal or threshold temp. Warm is the greeting your feet receive that brings the smile. This is what we'd like to have happen in the morning and must come mostly from stored energy or backup. I try for that mostly in the Master Bath and Kitchen. It's a temp around 75 or maybe 80. By the time the floor gets to 85, you cannot comfortably stay in the room for too long. Bathrooms floors are nice at that temp for showers, but impractical. This is why delivery temperatures can be as low as 90 and still heat the house, but 120 or so, is much better for recovery. Temps above that bring potential problems, but very fast recovery.

As far as photovoltaic collectors go, no, I never considered using them for resistive heating. A few years ago I helped design and install a ground heat source radiant system for my neighbor. That would be a nice application for electric panels. But for me, I'm not ready for that setup yet. I've seen very poor systems, good systems and systems where it could not be determined if they were working or not. When I start factoring in the initial cost, the warrantee and roof situation, maintenance, inverter reliability, permit costs and the actual proven savings, I just decide to wait a bit longer and work on the proven and simple thermal systems I know and love.