Most economical in floor heating

cdjja

We built a 40 x 96 x16 pole barn/shop in Midwest Michigan. Now we have decided to put in floor radiant heat. I am looking for any recommendations for the least expensive, diy way to install and heat. I have read many articles, and it has only made me more confused. We will have the walls done with 2" closed cell spray foam (there is tyvek). No windows, 2 overhead insulated doors 16x14, 14x14, and 1 man door. We will attach a metal ceiling to the underside of the trusses, and install fiberglass insulation R-13, 2 layers deep. We are only wanting to have the shop temperature to be around 50°. The cement will be 6 inches deep. Any help would be greatly appreciated. Thanks

Hot_water_fan

Inexpensive and in-floor heat aren’t usually compatible - there’s not much to cut here. You will have a boiler, a manifold, a circulator or two, 13 loops, etc. You can try to heat less of the floor and put other types of radiation instead. Or lengthen the loops/increase the spacing and accept wider temperature fluctuations. A temptation will be to use something that’s not a boiler (like a tank or tankless domestic water heater) but resist this urge. I think you can greatly improve the insulation. R-26 for a ceiling is very low and the slab isn’t even insulated? 

Will the shop be heated 24/7 or just as needed? Heating 6 inches of concrete (192,000 lbs) will take a very long time, so it’d be more convenient to keep at a constant temp if you go the in-floor route. 

hot_rod

The concrete is your heat emitter, so the cost of the insulation, tube, heater and pump are the variables, they cost what they cost Not many places to cheapen that list of parts.

Cheapest heat is probably a suspended unit heater, maybe a tube type over-head next.

Floor or ceiling radiant brings the comfort component into play. If you just want warm air temperature, any furnace of blower unit will do that for cheap.

cdjja

I guess I didn't word my question correctly.  I didn't mean inexpensive as by being cheap. I just meant not fancy straight forward, no waste. I want to choose the best efficient, design, and product for the money. I have read about closed loop, open loop. The size of the pex 1/2 or 5/8. From what I read on this forum. I should use a boiler, not a hot water heater. It also seems like the number of zones makes a difference. The thickness of the foam board. I would like to install it myself. I understand that heating consistently makes the best use of the system. I can also bump up the ceiling insulation up to R-39. We initially were not going to install in floor heat, but it seems like it's a good way to make the shop more comfortable for the size of the building. 

HomerJSmith

1) The cheapest way to get the most value from your BTUs is insulation.
2) Do a building heat loss calculation. Then you can determine your BTU needs.
3) Once your BTUs are known, then you can choose your heating sys based upon material and labor costs, BTU delivery efficiencies, and operating time frame and operating costs.
4) Nothing compares to infloor heat in terms of comfort. What's the length of time you will be spending in there?

Note: Infloor is a slow to heat and a slow to cool down sys. It takes time. The sys that use is a value decision.

EdTheHeaterMan

Let's say you don't insulate the floor below the 6" slab. That will save you money today but will cost you dearly in operating cost over the life of the building. Use 1" foam on the perimeter only will reduce the operating cost some. Adding 2" foam perimeter insulation will save a little more. Placing 2" Foam on the entire floor before the 6 concrete floor is poured will cost more today but the operating cost savings will pay for the cost of that insulation just a few years or less.

Adding mesh to the slab and attaching the tubing to the mesh at about 2" below the slab surface is better than stapling the tubing to the insulation and having 6" of concrete above the tubing.

this picture snows the tubing attached to the insulation. This will make the tubing furthest from the surface of the slab.
This illustration shows both tubing locations. The tube in the center is a better location. This is achieved by fastening the tubing to 6" mesh reinforcement and suspended on spacers.


The last illustration shows a Best Practice design for radiant tubing in a 6" slab.



EDIT: Get the floor right the first time. If it is wrong, then it will wrong for a long, long time.

Hot_water_fan

I guess I didn't word my question correctly. I didn't mean inexpensive as by being cheap. I just meant not fancy straight forward, no waste. I want to choose the best efficient, design, and product for the money. I have read about closed loop, open loop. The size of the pex 1/2 or 5/8. From what I read on this forum. I should use a boiler, not a hot water heater. It also seems like the number of zones makes a difference. The thickness of the foam board. I would like to install it myself. I understand that heating consistently makes the best use of the system. I can also bump up the ceiling insulation up to R-39. We initially were not going to install in floor heat, but it seems like it's a good way to make the shop more comfortable for the size of the building.

Smaller tubing will use more pumping energy, but is cheaper upfront. Usually loops are 300', so you'll need 13 at 12" spacing. If it's all one temperature, then you can avoid using zone valves or zone circulators and could DIY a manifold if you wanted. You'll use a closed glycol loop with a boiler. You can use a condensing boiler for max efficiency or a non-condensing boiler. Both have pros and cons. The floor temp to maintain 50 degrees indoors will likely be 55-60 degrees at design temperature, so not exactly warm and it depends on the structure's final heat loss.

Jells

I'm confused. Didn't you already pour the floor if you "built" it already?

Big Ed_4

Best off designing for a higher temp , easier to turn it down then add later ....

cdjja

Thank you for your help

veteransteamhvac

Eric Aune (Instagram superstar )recently built himself a shop/warehouse in Minnesota with concrete slab radiant floor and his project sounds very similar to yours. You might peruse his feed there (and maybe he's on Facebook also - I don't know) to see how he handled it. He obviously did most of the work himself on his off days, but what he did made sense to me. If you're willing to act as your own general contractor and perform some of the work yourself his experience might be a good roadmap.

GroundUp

First thing, double the insulation in both the walls and ceiling. Blown-in will be far less expensive and labor intensive for the lid than the batts you mentioned. Minimum of 2" foam both under and around the slab perimeter, this is not negotiable with floor radiant. I do in-floor in 30-50 buildings like this per year here in MN (actually just finished a 50x90 yesterday and started a 50x80 today), and personally I would use 10 loops of 5/8" pex at 400ft each, 12" apart. The 5/8" costs a little more upfront than 1/2" would, but allows longer loops and therefore fewer loops which cuts back on labor and ultimately allows a smaller pump and manifolds- meaning you recoup the cost of the more expensive tubing in the long run anyway. As others have said, a condensing boiler is probably going to be the best route here and with an open space like this, they can be made pretty simple and straightforward. If you would be interested in a prefabricated DIY system, I do custom build those in-house and ship to clients for site connection to gas, power, intake/exhaust, pex, etc which saves quite a bit of money for the homeowner willing to put in some sweat equity. Gas should be inspected and startup performed by a professional with a manometer and combustion analyzer, but the actual install of my DIY systems can be done by just about anybody who owns a screwdriver. I've got about 20 of them across Michigan and many more throughout the rest of the country. Please feel free to look me up if you would entertain such a thing- I would also set you up with the pex and materials for that DIY installation if desired.

cdjja

Jells, they will be done today with the building, but we're not pouring the floor until spring.I

neilc

make sure the walls air seal to the roof, and floor

pecmsg

Most economical

pot belly stove!

almost no install cost

wood is cheap

hot_rod

A bottom treated wood 2X between all the posts, insulate against that with 2" foam for the edge detail. However that foam edge will be seen inside, so metal L flash it or an insulation detail on the outside.
With siding already on the outside foam detail would be a bit trickier. We had the metal supplier bend a deep Z flashing to cover the edge of exterior foam, and hide the 2" edge.

Or better yet, spray foam that bottom 12" the thickness of the posts for a really good edge E value. Rigid board foam would work..You will pour against that so batts are not an option.

Most metal building erectors have details for radiant slab insulation, it is a common heat in metal buildings.

leonz

In my opinion,

A steam boiler feeding dry steam to forced air garage heaters will be the least costly way to do this.

You intend to heat an area that has a total volume of 61,440 cubic feet to 50 degrees. This is a very large area to heat to fifty degrees.

A steam boiler with 170,000+ BTU with the correct size twin riser pipes, properly sized drop header pipe with the double drop header pipe being one size larger than the twin riser pipes, properly sized air vents and take offs for the steam to air garage heaters can do this.

Things to know about steam:

A larger heating area requires less steam pressure for the same heat transfer rate, and because of this the steam pressure is less and the heat exchanger LMTD (Logarthmic Mean Temperature Difference) will also be less.

To learn more about this go here;

www.heatinghelp.com/systems-help-center/steam-velocity

Consider this fact in your thinking, the entire Empire State Building is heated using less than 2 pounds steam pressure.

Paul Pollets

Like HR said, there are cheap ways to do this, but RFH is the most comfortable. You're looking at a condensing gas boiler around 80K btus, if the insulation values are R21 walls and R30 roof and an insulated OH door(s). The slab temps psf may be signicantly less then 20 btus/SF with proper loop design and insulation.