Radiant Floor or Big Radiator

If it were just a shop.....I'd go radiator. Will the shop be occupied daily? That in-floor setup would take a long time to come up to temp. So if the shop is what I would think of as a "shop" I'd say go with a heat setup that allows for more flexibility and a little quicker "on" time.

But if the shop is getting regular use you can probably save some BTU's going with in-floor since it's quite efficient.....

Ditto on the slow response of a radiant floor. Unless you want to keep the building warm 24/7, radiant floor has a real slow response time (most folks dont use a setback thermometer for radiants). There is also a continuous pump load whenever the system is on. The trade off with a radiator vs radiant is that you can typically run a lower temp in the building with radiant as the heat is coming off the floor. It also works better to melt off any snow that accumulates under vehicles if you are working on them. If you ever plan to put in hot water storage or try your hand at Solar heating, go with radiant as you can get away with a far lower temperature. You will want antifreeze in the system.

With either system, its going to be interessting how you get a good insulation system in on the edges and of the new floor with the exisitng building in place.

Ditto on the comfort at lower temp point. Especially in a shop, I'd MUCH rather have a 70 degree floor and 50 degree air than a 50 degree floor and 70 degree air. Many shops suffer from thermal stratification where there's a blanket of hot air near the ceiling so that your head is sweating, and a cold layer at the floor so that your feet are freezing. Radiant solves that.

From the personal comfort perspective I think nofossil is correct about hot face/cold feet, especially with that tall ceiling height. You might need to be 12' tall to get your face to sweat. So that would argue for radiant floor.

I don't know that you're in an either/or situation. Why not both? Use the floor for primary heat and yank the batts off the propane tank to warm the space more quickly if you have let it cool off for a while. It's worked for you so far; and you're already trained.
With the larger, taller space the propane radiator may not be as quick to warm you as you're accustomed to. More radiator at the other end of the building? Definitely 3-speed reversible ceiling fan or two.

Unless the building is very well insulated (ceiling, walls and under the floor and its edges) and you tighten up the air infiltration losses (poly vapor barrier all around) stee has a good argument for radiator heat. The time lag of heating up all that concrete will frost your toes if you don't have it running all the time, and therefore losing heat all the time you're not in there. But by the time you put in enough radiator (or fan coil, the standard Modine arrangement) to efficiently use lower temp water from storage you might have matched the cost of the tubing in the floor.

If you go radiant floor, the long term efficiency/cost benefits would probably argue for a temperature mixing valve run by a control with outdoor reset. Just keep changing the temperature of the circulating water to match the heat load. The circulator in a system like that can run almost constantly for months. That argues for more loops/shorter loops for lower head loss and therefore less circulator energy. Same amount of PEX but more money for manifolds and valves.
It just keeps adding up to more money up front to be more efficient.
How much money can you afford to save?

The worst part of your dilemma is that the tubes can't be put in after you start wishing you had put them in when you had the chance. Ask me how I know.

if im working in a garage...id MUCH rather lay on a warm floor than cold. just make it a closed separate system and use antifreeze.

I would definately go with the radiant floor option. So many benifits as mentioned above.

The only thing I disagree on is that it always mentioned that the heat recovery takes so long blah blah I have not found that to be any differant than trying to heat the air with an forced air furnace when you open the door at -40.

I have two shops the one with radiant floor heat is by far the nicer to work in wether I am there all the time or not, it is easier to maintain tempeture when away with floor set on low.

Depends on how you use the shop, how often, what you plan on doing in there. I rarely keep my shop above 65F. Easy to do and maintain with radiant floor. If you plan on standing and working in there in the winter, no question radiant is the way to go.

A mix of radiant and fast recovery emitters is nice. In shoulder seasons a hydronic fan coil warms quickly, and can dry out the shop in humid conditions, turn the air after painting, etc..

Consider a wide spacing, maybe 18" on center, glycol in the loops, and a large hydronic unit heater. Tighten up tube spacing in front of the work bench.

If it is wood fired, maintaining the space at 60- 65F with radiant is not hard or expensive.

IfI had a dollar for every shop owner that regret-ed no tubing their slabs....

hr

Jim:

I have worked in both kinds of shops and like was said before, heated floor is much better. It's amazing how warm a 50* floor is compared to 50* at 5' above the cold concrete floor. I am finishing my 40 x 100' building this winter. Shell is up and floor is poured. I put pex in the floor of the shop and the "Recreation" area and left the cold storage cold. I haven't aquired a heat source as of yet, but considering a combination solar/owb or possibly geothermal. I plan to keep the place around 50* and if I want it warmer fast, I'll have a hydronic radiator to take the chill off.
I would recommend the in floor if you can afford the extra initial expense.

Stay warm.

JB

Everything I've seen on the subject says to put the PEX in the floor even if you aren't sure you'll use it - as you can't put it in later, and it doesn't add a huge amount to the upfront costs...

If you are using it for a wood shop, I'd especially be inclined to go with in floor, as I'd expect your wood work would like it better if you kept it in a relatively stable temperature.

Gooserider

Perhaps not either- or-- but some chosen integration of both.

Since, as mentioned, radiant floors cannot respond quickly, you could keep the floor at a fixed temperature that might not be sufficient to heat the full space-- and then go with some form of faster-responding "upper" source to bring the area up to full temperature during the times that it is occupied.

Having a floor that is not a heat sink- but instead gives off some warmth seems like it'd be a great feature.

Having the "dual mode" approach would also get away from what (with radiant floor only) would be the need to keep the whole area up at top temperature all the time due to the huge mass/ slow response of the floor.

Anyway, that's my $0.02 for you

I have a 40x100 shop with radiant heat. I keep it around 50* and most people think it's a lot warmer than that inside. When it's 10* outside and you're working on a floor creeper, life is much easier. Just make sure you use good insulation on the outside edges and underneath.