Hydronic Radiant Heating for Pole Barn - What is best heating source option

tjlively1

I am looking for some options for heating my 36 x 56 x 14 pole barn which will have a hydronic radiant heat tubing installed in the next couple of weeks. I will have a vapor barrier, 3" of foamular 250 insulation, wire mesh with 5/8" pex raised on risers to 2" and a 6" concrete pad. I plan on installing 1 to 2" of insulation on the edge of the pad before backfilling. Pex will be installed at 12" spacing. Ceiling and walls will be insulated, but not sure what R value yet - likely up to 30 on ceiling and 15 on walls. Climate is St. Louis, MO and the shop will only be needed to be heated to 60 degrees or so. Not a daily use shop, but I understand once you heat your mass you should maintain the heat. Also plan on having a finished loft 16x36 that I would like to heat and cool (could use mini split or window AC/heat unit or add radiant to the floor with a window AC). Currently electric rates for electric heating from my coop is at 6.2592 cents/Kwh.
We only have electric onsite and would rather stay away from adding a propane tank unless I am forced...

Some of the ideas I am floating right now:
1.) tankless electric water heater - Not sure longevity of this install as I have heard some people replacing fairly frequently.
2.) Geothermal - thinking water to water or a combination unit. I can install loop myself with help from friends and a backhoe, but would need to buy the unit and have a professional hookup. Also if installing a combination unit I could heat and cool the loft as well...Problem with this option is tax credits expired as of 12/31/2016...
3.) hybrid water heater or standard electric water heater - not sure if these units would keep up with the heat demand - experience anyone?
4.) Electric boiler - Cost for size needed and energy usage? Propane boiler if I have to for cost and efficiency.
5.) Would consider solar water, but not sure how it performs and the overall costs...
6.) Compost hydronic heating - install large compost pile and cycle water/glycol through manifold and pex tubing in floor...Jean Paine method - It's free (except mine and friend's time and labor) and usually lasts 12-18 months for heating... I only need about 4-5 months of heating...

Any help would be greatly appreciated. I would love to hear some of the costs associated to installing and operating some of the options above and whether you are satisfied with its performance.
Thanks.

Rich_L

Geo water to water; that's what I installed in my home 11 years ago and have been reasonably satisfied. I have in-floor radiant through out and forced air AC with a water coil in my air handler. Not sure I'd do it again even with the rebates. I've had just a couple of minor issues but if you have to hire that work done, it can undo your geo savings pretty quickly. I've also heard of quite a few that aren't living up to the originally quoted savings or life expectancy.
If I were building right now I would go with a Navien NHB wall hung boiler. It's gas fired though. I've had great experience with those and have a good friend that uses one in his shop, laid out similar to the description of yours.
Your electric rates are very reasonable so a very simple and cost effective installation could be to go with a wall hung multi stage electric boiler. Something like a Stiebel Eltron Tempra 36 B. Given your desire to stay electric and avoid gas, that would be my recommendation. Note, this unit is just an example and NOT sized to your building's needs.
I would definitely not recommend a domestic water heater. They simply are not designed for space heating, even though there are some out there being used for that. That said an electric may fare better than gas, with the needed water temps of radiant. Flue gas condensation would not be an issue in an electric domestic tank type of water heater.
I would go with a mini split in your loft to provide both heat and cooling. You could also make that another zone and put a loop up there too.
As far as costs of installation, GEO is usually the highest up front, the gas and electric would likely be similar. Running a gas line or extra conduit and wires...

kcopp

Have you done a heatloss on the system...? Cant just throw the tubing down and hope it will work.
You need to figure that out first before you figure out what type on boiler you need to do.

hot_rod

Air to water offerings are increasing. I'm near Springfield MO and get a good portion from passive and active solar

Load calculator, best insulation methods are critical details

tjlively1

Ok so I did a quick heat loss calculation found on usboiler.net and came up with the following. However, I am not sure what the H.M. is for the floor as it asks for no insulation, overhang 3", 6" and 9". Not sure what overhang is referring to. I assumed it was the amount of insulation under the concrete so I went with 3". You will also notice that my window and door area is quite large as I have two 14'x18' doors, seven 3'x3' windows, a 1'x6' transom window and a mandoor... As I mentioned above I am hoping to have 15 R value insulation in walls and hopefully 30 total in ceiling.

hot_rod

Single pane windows? I think the selection you chose is for single pane? Try it with double. Looks like you have more like 70 square feet of glass?

Hopefully the large doors are insulated, that would be closer to 2" wall value, not the glass value.

tjlively1

I recalculated it with what you suggested hot rod.

hot_rod

Does the program allow for slab on grade, looks like a framed floor with overhang in your example? Your window and door load seems way high.

Without all the building data I tried

R15 walls, R 30 ceiling,
546sq' 2 large and man doors, at R 3.6,
70sq' window R3.6
2" foam under and around slab,
.7 ACH
and come up with 53,000 BTU/hr load.

Which is around 26 BTU/ sq foot, reasonable for that size building and doable with radiant.

I doubt the load is 87,000 and it would not be possible to heat with radiant floor if it was?

Harvey Ramer

You really should be using a program designed for radiant. This one is very good and free. http://www.uponorpro.com/Technical-Support/Downloads.aspx

Uponor Advanced Design Suite

Mark Eatherton

If I were you, I'd idle the place at 40 degrees when not using it then turn it up 2 days before you need it. As for source, I'd go cast iron electric boiler. Simple, sweet and relative inexpensive.

As for solar thermal, absolutely. If you can do a lean to ground mount, just tie the collectors in and let them do the day time maintenance. I had a student once who had a 36 X 36 garage with this style of system, and he raised earth worms in there and claims he never lost any worms due to freezing. It can't go much below 40 or the worms die from the cold..

As for loads, if you size the boiler at around 30 btus per sq. ft. You will have a little excess recovery capacity in case you forgot to turn it up... We refer to it as acceleration factor.

As for the loft, I'd go with a min split and be done with it. Radiant cooling is great, but controlling the relative humidity is required and tough to do in that kind of environment. You could base load the garage floors with it by keeping them at 70 degrees F.

ME