So overwhelmed! Guidance needed :(

[ToddWebb]

Hi Hearth Board,

Newbie here, about to move to farm country. I'm stumped on the myriad heating options.

Lil' backstory: I bought an empty lot near Gettysburg PA. I'm about to build a pole barn (professional builder doing that). We can expect 3 months of freezing weather each winter. I will live in this barn for two years while saving/planning my future home. This barn will be my primary place of work, and my brother's, even after I move into my future home, so the barn will be climate controlled, always. The barn will have a small office (ie: bedroom) and full bath, other than that it's 16' walls, 4,000 sq ft fully open space.

We're going with radiant floor heating - that's settled. We're heating the pipes from outside the barn - that is also settled, I think.

I think we want a combo log/waste oil burner. We'll keep it fueled with oil for those days we don't get around to stoking the fire - that could honestly end up being 3/4 of the time. We have 12 acres of woods, but will also buy firewood (because we're lazy city folk).

That's what I know. Here's what I don't know:

• Is a log-burner (over wood burner) advisable? So that we can use larger logs, and spend less time chopping wood? I see a lot of online info about wood burning, of course, but the word "log" rarely comes up.
  
• Is a dual-unit ideal? Or two separate units better?
  
• I assume the boiler(s) must be set onto a concrete pad?
• Do these boilers just sit outside? Or must I build a shed for them?
• How large a boiler do I need? How do I determine if a particular model is big enough for my needs?
• What type of thermostats should I use? Measure the room temp? Measure the floor temp? This barn will have no air ducts.
• Brand suggestions?
• How far away must the boilers be from the steel pole barn?

Ack! I'm overwhelmed and out of my comfort zone. This is a huge investment. I'd really like to get it right.
Thank you.

 

[JP11]

Logs= unsplit WET wood. Read, inefficient wood burning.
Quite a combination.. waste oil and wood. Waste oil furnaces usually require a compressor. Do you have a source of waste oil?
You're talking about a lot of weight.. for sure on a pad. I'd recommend it's own small shed with SPLIT dried wood inside.
You need a heat loss calculation on the building to size the boiler
If you're living there, you'll care about the air temp, not the floor temp.
Brand doesn't matter near as much as TYPE of boiler and sizing of pumps, spacing of in floor pipes and length of runs in manifolds. This stuff is SCIENCE.. you can't hope to have good results without doing the math!
Not sure about your codes for distance away from barn.

My recommendation.. keep reading here.. A BUNCH!

JP

 

[ToddWebb]

JP11 thanks.

I was under the impression that heating the floor also heats the air. No? Some locals I've spoken to (mostly mechanics) said this is the case. They also say that every time a client's car drives into the shop it lets all the hot air out which takes forever to replenish but those with radiant floor re-heat much faster. Am I putting too much faith in empirical info?

No source for waste oil yet, as I don't live there yet. I was also under the impression that a waste oil burner could accept new, clean oil as well. No?

Build a shed on a pad - cool, no problem, I can do that!

Floor will be 5" thick 4,000 psi concrete (brother's UPS truck will park in there frequently). Floor pipes will be 1/4" looped no more than 300' lengths, and run every 12". Floorspace is 46'x88'.

 

[Floydian]

Hi Todd,

Radiant floors will heat the air as well as the the objects that the floor can see. The convective currents are minimal so you wont really feel them. High mass radiant floors are great in situations with lots of opening and closing of large doors. Heated objects wont lose their heat very quickly which will keep you more comfortable.

As far as 1/4" tubing, I hope you meant 1/2", up to 300' loops, which is standard. Spacing, flow rates, supply temps, boiler sizing, pipe sizing etc. are all determined from the heat load calculation that JP mentioned. Very important-the foundation of any properly designed heating system.

Various online heat loss calculator out there, just remember, garbage in, garbage out. So you need to be as accurate as possible. And air seal that barn as well as you can and consider your mechanical ventilation system as well.

Also, slab edge and under slab insulation details are also very important to get right. A few ways to do it right and lots of ways to mess it up.

Lots of great info on various low energy details here: http://www.greenbuildingadvisor.com/ . Use the search bar there and right here.

Good luck,

Noah

 

[711mhw]

What he ^^^^^ said!! And I'll add that I would seek out a radiant designer. I'm not one to "hire out" much work, but I did spend the money on a professional design and have never regretted it. They provided me with drawings complete enough for this carpenter to install the whole system. He'll ask you for your wall construction (insulation value's) and should also ask about your heat source. Along with a bunch of other things about what type of controls (automatic switching over from your wood to backup) as well as making suggestions. They don't need to be local. I used to live nearby (MD) and they don't do much radiant there, and those that do charge a lot. Don't let anyone talk you out of under slab insulation & frost walls!
Reading your first post make's me ask, have you checked into geo thermal? Wood burning requires a big comitment, all year long!
I heat my shop with a wood boiler & radiant and love it, but I am mostly retired and have the time and equipment to make my own fuel.
You're on the right track, keep asking questions and keep on with your "homework".

 

[BoilerBob]

You can't heat 4000 sq ft with 16' ceiling with wood or logs if you are "lazy".
.
I suggest PELLET boiler.

 

[Boil&Toil]

1/4" definitely does not fly. There's good arguments for going with 3/4 rather than 1/2 - heck of a lot less head, which means more pumping for less power. Since your pumps typically run 24/7 in heating season, energy saved on pumping is smart savings. You'll notice EW didn't even calculate for 1/2" https://www.hearth.com/talk/threads/pex-pump-tables.142352/ And yes, if you are "lazy" burn pellets, not logs or waste oil, especially if you don't have a self-generated stream of waste oil (waste oil burners are not a particularly efficient way to burn non-waste oil - and pellets are lot cheaper than oil.) 12 acres won't keep you in wood for long...

Most "pole barn people" may not really grasp insulating well - a radiant slab needs good insulation underneath and all around the edges to work well, and your walls and ceiling also need a good deal of insulation to let you save any money towards an eventual house, especially when you have that much area to lose heat from. 46x88x16 = 3,552 square feet of wall, 4048 square feet of ceiling. 5350 heating degree days. 19,516,800 BTU/year if insulated to R50. 39,033,600 if insulated to R25. 3 tons of pellets might do it at R25, or not depending on how the slab is done, air leakage/ventilation rate, doors and windows, etc.

 

[JP11]

I usually tell people.. no woodlot you own??? go pellet boiler.

 

[711mhw]

air leakage/ventilation rate, doors and windows, etc.

O.H. (garage) door's, I've never seen a "seal" worth a chit. My 3 doors have 156' of "air leakage". Kinda makes the 3" of foam in the walls…….

 

[Boil&Toil]

^^ I got an actual Overhead Door (brand) Commercial insulated (R-17) 10x10 door. It seems to seal pretty decent (they installed it, too - best $1100 I spent on the building - kinda made me wonder if I should have got a 3x7 from them instead of the wonderful R-4 man door I did get (forget the brand, but a well-known one.) Certainly could suck rocks if done and/or adjusted poorly, though. I know I spent some time getting the opening up to their spec before they showed up.

 

[ewdudley]

You'll notice EW didn't even calculate for 1/2"

Those charts are aimed calculating flow for the boiler-shack-to-house loop.

In-floor 1/2" PEX will have multiple 300 foot loops in parallel. I think the 300 ft number comes from the fact that 300 ft is about a long as you can get with 1/2" PEX and still easily meet the RPA rule of thumb of 0.6 gpm for 1/2 PEX.

Here's a table for 15 300 ft loops in parallel, which should be about right for 4000 sq ft. With that many loops I assume there would be a circulator pump and a separate injection pump. Once you feel you understand the issues involved you should probably get a pro to do your design, I would assume there's a lot of opportunities to make improvements that would come much more easily to those more familiar with the ins and outs.

Again, there is a fair amount of guesswork in my wattage numbers, but the ECM pumps appear to be twice as efficient as the venerable PSC pumps. (Efficiency here is given as gpwh, gallons per watt hour). But with multiple zone valves or TRVs you'll be going with a deltaP ECM pump anyway.

pipe: PEX_0.500 x 300 x 15; diameter: 0.475 in
  fps  psi    head  gpm  watt gpwh %gpm pump
1.32  2.76    6.37 10.91    86  7.6  76 Taco_008
1.36  2.91    6.70 11.24    44 15.3  73 Taco_VR1816-V
1.36  2.93    6.75 11.28    86  7.9  49 Taco_007
1.37  2.96    6.82 11.35    60 11.4  81 B&G_Vario-VII
1.38  3.01    6.95 11.47    86  8.0  68 Grundfos_15-58-III
1.39  3.03    6.99 11.51    59 11.7  72 Wilo_ECO_16_Stratos-V
1.44  3.21    7.41 11.90    45 15.9  50 Grundfos_15-55-Alpha-III
1.44  3.22    7.43 11.92    58 12.3  66 Taco_VT2218-IV

 

[woodsmaster]

Insurance companies around me want solid fuel appliances 30' from any other building.