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Pole building heat configuration

EricL Member Posts: 1
All – I would like to spend 2 cents here to get opinions on setting up my pole building heat configuration.

Requirements: Heat building to 60 degrees in the Iowa winters.

Building information: Building to be started in April here in northern Iowa. Size 60x72x18 insulated(R-38/R-50) with 8 3x3 windows and 2 doors. Also included two 12x14 insulated overhead doors and one 8x9 insulated overhead door. 2” rigid insulation will be installed with a combination of 6” and 5” thick concrete flooring. This will be an open building to start. Then down the road I plan to install a bathroom and mezzanine. Primary functions for this building is 1) storage of cars, rv and other toys. 2) working on said items. 3) family events.

Current plan:
If I put in the correct inputs I should have around a total heating load of around 100,000 Btu/Hr – Does that make sense?

One zone with 9 circuits using 5/8 Pex averaging 400 ft per circuit. Does this make sense?

Circuit # Length (ft) Tube Type Flow Rate (USGPM) Head Loss (ft water) Req. Water Temp (°F) ΔT (°F) Total Load (Btu/hr) Zone Name Room Served Reynolds #

Water Temperature (107.0) 8.28 11.2 107 89,936
Manifold 1 9 Circuits 8.28 11.2 110 89,936
Circuit A-1 423 hePEX 5/8" 0.96 9.1 110 25 10,469 Zone 101 Room 1 2633
Circuit A-2 398 hePEX 5/8" 0.91 7.8 110 25 9,916 Zone 101 Room 1 2496
Circuit A-3 377 hePEX 5/8" 0.87 6.9 110 25 9,466 Zone 101 Room 1 2384
Circuit A-4 394 hePEX 5/8" 0.91 7.7 110 25 9,913 Zone 101 Room 1 2496
Circuit A-5 395 hePEX 5/8" 0.91 7.8 110 25 9,901 Zone 101 Room 1 2496
Circuit A-6 401 hePEX 5/8" 0.92 8.0 110 25 9,970 Zone 101 Room 1 2510
Circuit A-7 402 hePEX 5/8" 0.92 7.9 110 25 9,943 Zone 101 Room 1 2502
Circuit A-8 402 hePEX 5/8" 0.91 7.9 110 25 9,904 Zone 101 Room 1 2496
Circuit A-9 427 hePEX 5/8" 0.96 9.2 110 25 10,454 Zone 101 Room 1 2633

Boiler: I have not looked into yet, until I understand the above is correct.

I have time to make this right. I want to balance my spend vs the best system. Comments are welcome and requested.

Best regards, Eric


  • WMno57
    WMno57 Member Posts: 1,228
    More insulation under, and along the sides of the slab. At least 4 inches. Plan a spot in the slab for a car lift. The slab may need to be thicker in this area. Keep the pex away from where the anchor bolts for the lift will go. Take pictures after the pex is installed, but before the crete is poured.

    You may want to keep the bathroom warmer than the rest of the building. Separate zone?
    I DIY.
  • GroundUp
    GroundUp Member Posts: 1,865
    96k seems about right, maybe a little steep given the R38 walls but in a single zone it won't affect much of anything to oversize a bit. I'm not liking the 15" spacing or the 40% PG though, if it were mine I'd add more tubing and drop the PG to 30-35% unless you plan on letting the building get -25F inside. Keep each loop under 400ft and add 2 extras would be my recommendation, for a total of 11. More emitter = lower water temp = higher efficiency.
  • EricL
    EricL Member Posts: 1
    @WMno57 - Thanks for the advice. I will look at adding more insulation, if only around the sides. Monies well spent.
    As for the lift I am currently leaning to 4 point lifts that are mobile and do not require thicker concrete. I read somewhere to put most items in your new shop on wheels and wait to build interior items, until your sure on your actual needs.
    I will be documenting the build with many pictures.
    For the future bathroom I will be roughing in the plumbing and thought the zone would be to small. Am I incorrect?
  • EricL
    EricL Member Posts: 1
    @GroundUp - I made changes per your comments. 30% PG, lengths <400 feet and 12” on center. Now I have 12 circuits. Here is the updated view.

    Circuit # Length (ft) Tube Type Flow Rate (USGPM) Head Loss (ft water) Req. Water Temp (°F) ΔT (°F) Total Load (Btu/hr) Zone Name Room Served

    Water Temperature (107.0) 8.04 7.8 107 95,363
    Manifold 1
    Circuit A-1 366 hePEX 5/8" 0.66 3.8 107 25 7,833 Zone 101 Room 1 2360
    Circuit A-2 400 hePEX 5/8" 0.79 6.1 107 25 9,405 Zone 101 Room 1 2834
    Circuit A-3 379 hePEX 5/8" 0.68 4.1 107 25 8,124 Zone 101 Room 1 2448
    Circuit A-4 359 hePEX 5/8" 0.66 3.7 107 25 7,817 Zone 101 Room 1 2355
    Circuit A-5 377 hePEX 5/8" 0.68 4.0 107 25 8,040 Zone 101 Room 1 2422
    Circuit A-6 350 hePEX 5/8" 0.65 3.5 107 25 7,657 Zone 101 Room 1 2307
    Circuit A-7 359 hePEX 5/8" 0.66 3.7 107 25 7,811 Zone 101 Room 1 2353
    Circuit A-8 363 hePEX 5/8" 0.66 3.8 107 25 7,880 Zone 101 Room 1 2374
    Circuit A-9 381 hePEX 5/8" 0.68 4.0 107 25 8,015 Zone 101 Room 1 2415
    Circuit A-10 356 hePEX 5/8" 0.64 3.5 107 25 7,602 Zone 101 Room 1 2290
    Circuit A-11 367 hePEX 5/8" 0.66 3.8 107 25 7,825 Zone 101 Room 1 2357
    Circuit A-12 348 hePEX 5/8" 0.62 3.3 107 25 7,354 Zone 101 Room 1 2216
  • leonz
    leonz Member Posts: 1,051
    edited February 2021
    If it were me;

    It depends on what type of concrete pour you intend to use; being a "Neat Pour" filled completely with concrete to the elevation you need for cinder blocks with a thick plastic sheet vapor barrier laid down before you lay the reinforcing rod/mesh down using wire to connect it together and blocks to elevate it above the vapor barrier after the foil backed styrene insulation is laid down and before the slab is poured.

    If you use hollow cinder block laid up to the sill plate elevation or a formed foundation slab that can easily be insulated with the foil backed polystyrene and then the block can be laid and filled with vermiculite after the final block layer is laid and the mortar is cured.

    You also have to plan on installing felt expansion joints between each pour to prevent cracking of the concrete and using a concrete vibrator to eliminate air bubbles in the concrete. If you use a strong sand mix concrete you will have many fewer air bubbles and the concrete will not wear so quickly.

    If you are going to have the slab and aprons properly insulated with the maximum amount of foil backed polystyrene for the building I would use single pipe steam heat and I will tell you why;

    I candidly think using steam heat would be better suited for this as it is brand new construction and the piping routes would be easy to install using black iron pipe for the low pressure steam header and drop pipes in my opinion.

    Installing the header pipe with capped Tees and couplings in short pipe joints to each eventual room circuit would let you plan first and then install the smaller steam drop pipes to each circuit as you grow with it.

    You would need the correct number of vents and the proper size vent for the header pipe installed and you would be able to employ a very large 3 inch+ drop header to make dry steam that will travel to the smaller radiators in seconds to push the air out of the radiators and heat them quickly.

    Your current plant is to use in floor pex using 400 feet per room/circuit? and you need either a circulator for each circuit or a zone valve and a single circulator to push the hot water through the slab in each zone at 4 gallons per minute from one header pipe then connect to the return header pipe.

    With steam you would be able to employ cast panel radiators in each zone hang them on the walls and use TRV's to control the heat emitted to each zone. What ever zone that is occupied can be heated and the rest of the zones kept at 50 degrees using TRV's

    WITH more planning and more capped tees in the header pipe when you install it you would be able to add panel radiators to increase the amount of heat provided in each zone.

    Gravity hot water heat would be easy to do as long as the return pipe to the boiler sump is in a perimeter trench along the sill and it could be covered using 2 by 12s and leaving the form boards in place to hold up the 2 by 12's at floor level.

    Each room or potential room could have one or more hot water radiators to heat it and the cooler return water would simply flow through the pipes in the trench slab from each room to the header pipe at the boiler sump.

    It would simply take a little more planning on where you intend to put things and what you intend to put where to route the return pipes under the painted 2 by 12 which is is all any one will see in the floor.

    Gravity hot water heat will give you huge amounts of thermal mass in the water that will radiate into the slab and each rooms radiator.. You would need to have an open to air expansion tank installed near the ceiling in the boiler room for the system to work correctly and to allow the cooler return water to flow to the boiler sump. The overflow pipe could be piped to a laundry sink in the boiler room and the system could be refilled as needed at the laundry sink as the over flow pipe coming from the open to air expansion tank would always tell you when it is full when you have water coming out of the overflow pipe. .

    If you add more capped nipples, tees and ball valves in the header pipe you can always add more hot water radiators in the future. As long as you have extra tees and capped pipe in the return line to the boiler sump.

    The water in the header pipe will be 170 degrees Fahrenheit as it leaves the boiler and goes to each room or radiator location.

    SO if you have in floor pex you have 3600+ feet of pex not including the return water pex connections to a header at the boiler sump and all the controls for each room or circuit. you may need the pex pipe sheets that lock the pex in place while the concrete is being poured.

    Are you going to heat the slab aprons to prevent ice buildup????

    If you use gravity hot water you have a single central header pipe with Tees and capped nipples and ball valves to each circuit and its radiator(s) with 170 degree water that is rising in the header pipe as the cooler water is returning and moving by gravity to the boiler sump header pipe from the return pipes in the floor that will also emit heat into the slab and room.
    Each circuit will have a TRV in each panel radiator or reclaimed hot water radiator to control the temperature in each room or area. You could heat the apron slabs with pex and a single small circulator fed from the hot water boiler to the aprons in one circuit.

    If you use steam you will employ a 3+ inch drop header to feed a single large header with branch header pipes and vents to feed dry steam at very high speed to purge the air from the radiators in each zone and fill them with dry steam with out water hammer and they will cool slowly. Each radiator will have a TRV so you can keep the temperature lower in each unoccupied zone or room.
    You could heat the overhead door approach aprons using the hot water in the steam boilers sump using a mixing valve to keep the water temperature at 140 degrees and return the cooler water to the boiler sump using a pex line hung in the ceiling and routed back to the steam boiler sump connection.

    You would need a steam boiler large enough with enough water capacity to warm all the approach slabs at once with a single circulator and still create enough dry steam with its 3"+ drop header to heat the building with low pressure steam of 1 to 1.5 PSIG.

    New construction lends itself to steam heat or gravity hot water heat with less work and less plumbing.

    There are a bunch of videos on you tube where a gentleman is using refrigerant grade coiled copper pipe to connect to his radiators from the header pipe in the basement and the steam flows to them with no issues or leaks so that may be an option to think about.

    The tees coming off the steam header pipe would have to be 30+ degrees below horizontal or more to allow the dry steam to travel down the refrigerant grade copper coil pipe to the radiator from the ceiling. The size of the main header pipe and vent or vents would depend in the length of the header pipe and the branch pipes to the heating zones in any case.

    Using a one pipe dry steam system eliminates the need to have a return line to the boiler and it will quickly heat the radiators and they will cool down slowly and the steam boiler will cycle on an off less often with a heat call. I think I have that right I hope.

    Its fun to think about anyway.
    JUGHNE Member Posts: 11,021
    Bathroom floor usually too small to get enough heat supplied because of fixtures etc.
    I heated all the floor possible and also wall heat installed.
    Extruded aluminum plates installed on the face of studs, well insulated wall behind them.
    Just don't hang pictures.
    If you know where the walls will be you could stick a loop up between studs on a couple walls. Leave it a single piece for each wall back to the manifold for pressure testing.
    Then when time for walls, cut the loop and complete it thru the wall.
    You could also set bolt anchors in the concrete where the walls would be, don't want to be drilling into your slab later and finding some tubing.
  • mattmia2
    mattmia2 Member Posts: 9,412
    edited February 2021
    If you will be opening the doors frequently you might want to add some fast responding emitters and some extra capacity to heat the cold air the doors let in.

    Also remember that radiant, especially in a slab, does not recover quickly, it could take days to heat it up if you use a setback when it is unoccupied for extended periods or you don't heat it at all. radiant wants to keep the building at a constant temp.
  • WMno57
    WMno57 Member Posts: 1,228
    Eric, if you tell us more about the mezzanine and family events, you will get some good advice on the heat setup.

    Will the mezzanine be finished space for social gatherings or storage for car parts?

    My thought about keeping the bathroom warmer is because I think once you start paying the heat bills, you might decide to keep the slab at 50 instead of 60. Also in the event of a outage, you want the bathroom to freeze last. Electric baseboard? Will there be an office or entertainment room that would be kept warmer than the vehicle storage space?

    I would make the rv door 14 feet tall (13' 6" max rv height). I would make all car doors at least 9 feet wide and 8 feet high (size for full size pickup truck).

    Four post lifts are for stacking cars for storage. Two post lifts are for working on cars (think taking off wheels). You, or a future owner will eventually get a two post lift.

    You may want AC in the entertainment room.

    There will be humid Summer days when the temp inside is below the dew point. Having too many doors open for too long will bring in humid outdoor air which will condense on everything inside your building. First time this happened to me it looked like it rained inside my building. Not suggesting you AC the entire space, but you may want to wall off an area, or limit open doors on humid days.
    I DIY.
  • WMno57
    WMno57 Member Posts: 1,228
    Almost forgot. You really should have 4 inches of foam under the slab. Two layers of two inch is fine. The thickness of the foam on the side of the slab will be constrained by how it is trimmed to the siding. 1 inch is far better than nothing.
    I DIY.
  • EricL
    EricL Member Posts: 1
    @Leonz - Thanks for the different approach. I will watch a couple videos on it.
    @JUGHNE - I think if needed an electric heat supplement heater will be the most cost efficient.
    @mattmia2 - I only will setback if I know it will be a week or two away from the building.
  • EricL
    EricL Member Posts: 1
    @WMno57 - The overhead doors have setup are two 14 foot high by 12 foot wide. One for the RV and other for cars, trucks, tractors and such. I have a smaller one (8Hx9W) mainly for UTV, garden tractor and maybe will put a screen on it for air flow in the summer. We will see.
    A few times a year (no COVID) I have larger groups over at the farm. I have a small 2 acre pond. We fish, BBQ, play with UTV, 4x4s. Also I have a small shooting range. This building will move most people from going into the house. Then I will have the family events like birthdays, holidays and other get togethers over the year for 30-60 people.
    For the mezzanine no clue yet. I have designed it a couple of times, but stopped. I think its a next year project....
    The lifts will be for storage and some work on my cars. At first I want everything mobile.
    For the very humid days I know exactly what you are talking about. I plan to be floating on a tube drinking cold beers on those days.