Heating a shop

I'm building a shop behind the garage, but it is not connected to the house. Would radiant floor heating suffice if the shop is well-insulated? It seems the hot water heater, associated electronics and tubing might hit the right mix of cost (not too high) and safety ("go gas, go BOOM!"). I could put a wood stove in there, but not too thrilled with flames. The threads in R.W. go all over the place.
I live in Northern Maryland.
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On 19 May 2004 11:48:01 -0700, the snipped-for-privacy@adelphia.net (Greg Carter) wrote:

I heat a (18x16) 3000 cubic foot shop with a $50 electric fan forced 5000watt construction heater. We get the odd 30 below day here with long winters. The heater is less than a foot square mounted about 8 feet up. I have insulated 6 inch walls, insulated wood floor and 2 cheap ceiling fans to push the heat down. It's toasty warm.
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On Wed, 19 May 2004 19:06:42 GMT, snipped-for-privacy@excite.net posted:

So long as you have very cheap electricity. With a heat pump, you can get three or more times the heat from the same amount of electric, or the same amount of heat from less than a third of the electric. But then you have the capital cost.
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The potential problem is operating cost/comfort. If you plan to keep the shop heated al the time, it is a good way to go. I recall Norm building a shop (I think it was his own house) where the hot water ran from the house to the shop through a highly insulated pipe.
If you plan to have no heat except when you use it on the weekend, it is a poor way to go. Before you get any heat into the room, you have to heat up a massive amount of concrete. It is a slow response if you want to go from 20 degrees to 60 degrees to work for a few hours on a Saturday. If you want to keep the shop warm all the time, I think it would be a good method. Ed
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like ed said. if you plan to keep the shop at one warm temperature all the time, its a great way to go. if you want to turn it up and down its a horrible way to go. radiant heating does a good job of maintaining a temperature, but when you change the dial, it doesnt work very fast. if your shop gets down to 55F, it could be a day or two before it gets up to 70 again just from the floor heating.
randy

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Authoritative answer: "it depends."
Insulation is the _big_ issue. Including what you do about the floor.
Once the architectural/structural issues are settled, then you can start estimating the heat losses through the: floor walls ceiling, windows (as appropriate) doors (as appropriate)
How fast you lose heat depends on the quality of the insulation, _and_ the inside/outside temperature difference.
Figure temperature difference based on 'worst case' exterior temperatures for your locale, and _warm_ inside (like 75F). (even tho you won't usually have it that high)
That's how much heat capacity you have to have at an absolute _minimum_.
You want a heat plant with _at_least_ 3x that capacity -- so it isn't running *all* the time, just to keep up, on the worst day. HVAC design generally aims for a circa 25% duty cycle, under 'severe' (but not 'most extreme') conditions. e.g. runs for 5 minutes, off for 15 minutes.
Once the size/capacity of the heat plant is estbalished, _how_ you get that amount of energy into the space is a 'minor' consideration. *anything* that provides 'enough' heat will be sufficient for the task.
As for your circulating hot water system, (1) _How_ are you going to heat the water? (2) Does the water heater put out _enough_ heat (into the water) to equal the heating requirements (established above) (3) 'Apparently' you're considering an electric water heater (based on 'go gas, go BOOM' :). Cost out what that electric heater will cost to operate. and make sure you've got enough power coming in to the property to support it. in addition to current loads _and_ the new tools you'll be putting into the shop. (this may lead you to re-think the energy source.)
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Greg Carter wrote:

The other problem with underfloor heating is that you either have to use antifreeze in it or be _sure_ to either drain it or have it turned on any time the temperature goes below freezing. If it's in slab and the pipes break, it's a real pain to fix--I have a friend who lives in a house designed by her architect father who decided that it was cheaper to put in a warm air heating system than tear up the slab to find and fix a busted pipe.
If you don't want open flames, a mini-split heat pump might be a good solution--the condenser doesn't get hot enough to act as a source of ignition and it doubles as an air conditioner in the summer.
As far as the _adequacy_ of in-floor heating, the technology is ancient (look up "hypocaust") and can provide adequate heat in any climate and with any halfway reasonable amount of insulation as long as you can keep the water hot.
--
--John
Reply to jclarke at ae tee tee global dot net
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affect the strength of the concrete slab at all?
Charlie
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I live in Wisconsin and heat an 832 sq ft shop with floor radiant and love it. My heating season is nearly 5 months and we see -20 pretty frequently. Been heating and cooking on gas for over forty years and still here too... no bangs. Here's a couple of rough points. 1. Pex tubing is getting pretty inexpensive, put it in the concrete and you can always change your mind later as long as it's in. 2. New age pex tubing is incredibly strong listen to old "broken tube" in the concrete recommendations with a grain of salt. 3. Insulation and vapor barrier under the slab are very important 4. For me the heat goes on in November and stays on until March the earlier weekender comments hold value. 5. (Charlie) Concrete is likely stronger, rewire and rebar abound as thats how you tie and hold the pex in place. 6. 4" deep concrete minimum above the tubing incase you want to anchor something later, I also did detailed photos and mapping cause I will forget where that stuff was in the future. 7. Do your homework on zones it gets more hot water into the 'crete and if you do get a leak you just kill one zone without loosing the whole shebang. 8. I ran a loop under the door apron and some of the sidewalk so I don't even have to shovel. annual cost for heat is about $250
EJ
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