Shop heat question

-Finishing up framing a 13'x36' shop area within my large shop. Walls and 8 foot ceiling fully insulated. All surfaces are 1/2" -oriented strand board, along with a couple of double insulated windows looking into the bigger shop. There is 4" insulation in walls -and 6" in ceiling. Concrete floor with vinyl tile. Power available for heating would be either electricity or propane.

-Would like to maintain 50°F to keep machinery from rusting. Outside temperatures average around 36-38°F through the winter -months. I don't require a warmer temperature for working. Can always place a small propane heater next to me if I'm going to -stand in one place for a long time.

-All suggestions greatly appreciated. BTW, ceiling will have 8 four-foot four-lamp fluorescent lights.

-Thanks, Ivan Vegvary

I'm still looking for a gas or propane forge that doubles as a space heater.

jsw

nd 8 foot ceiling fully insulated. =A0All surfaces are 1/2" oriented strand= board, along with a couple of double insulated windows looking into the bi= gger shop. =A0There is 4" insulation in walls and 6" in ceiling. =A0Concret= e floor with vinyl tile. =A0Power available for heating would be either ele= ctricity or propane.

temperatures average around 36-38=B0F through the winter months. =A0I don't= require a warmer temperature for working. =A0Can always place a small prop= ane heater next to me if I'm going to stand in one place for a long time.

t four-lamp fluorescent lights.

Unless the propane heaters are vented to the outside, they will generate a lot of water vapor. I would recommend that you try to find some dehumidifiers. A couple of them will provide some heat as well as reducing the humidity. In your area I might try getting a couple of used window air conditioners and mounting them so they cool the large shop and heat the small shop area. I would think that would be more cost effective than electric resistive heating. In your area I think the cost of electric resistive heating would be slightly cheaper that propane.

=20 Dan

Would like to maintain 50°F to keep machinery from rusting. Outside temperatures average around 36-38°F through the winter months. I don't require a warmer temperature for working. Can always place a small propane heater next to me if I'm going to stand in one place for a long time.

All suggestions greatly appreciated. BTW, ceiling will have 8 four-foot four-lamp fluorescent lights.

Thanks, Ivan Vegvary

==========

Propane will produce a lot of water vapor, which will readily condense out onto any colder cast iron surfaces and cause rusting because of dewpoint issues and so I would seriously suggest using an electric infra red spot-heater instead.

Other than that, you can figure that for all practical purposes, your flourescents will be serving double duty as strip heaters--( not necessarily a good thing in summer but...) just calculate the total wattage of your lighting buss and go ahead and turn them on in advance--if you're insulated well enough then it could even be that's all you really even need.

Don't they all ?

foot ceiling fully insulated. All surfaces are 1/2" oriented strand board, along with a couple of double insulated windows looking into the bigger shop. There is 4" insulation in walls and 6" in ceiling. Concrete floor with vinyl tile. Power available for heating would be either electricity or propane.

Darn, for just a few bucks more, you could have framed it with tuba sixes (or double-stud walls) and needed even less heat to maintain it. I hope all your wiring is surface mounted, keeping heat loss from the inner building lower. Seal every corner, crack, and seam, top and bottom. The better the insulation and the lower the in/ex-filtration, the less HVAC system you need.

I'd go with electric instead.

I don't have the book for calculations. Manual J, "Residential Load Calculation," published by the Air Conditioning Contractors of America (ACCA), is the recommended method for use in the United States according to the gummint. They cost only $140!

my guessing at generic data, it looks like a 11654.392 BTUH loss. You could call a local HVAC guy and ask what HVAC system you need, or just get a 4kW heater from bLowes. Add a box fan to help destratify. It's large enough to warrant a full HVAC system if your pockets are deep enough.

four-lamp fluorescent lights.

I was paging through a woodworking book last night and the author had mentioned usint an additional switched 2-lamp 4' fluor over each machine. He powered the machine and the lamp from the switch. That couldn't be done with 240v single or 3-phase, but it's an idea.

(Pat Warner's _Getting the Very Best from Your Router_ book)

-- Live in the sunshine, swim the sea, drink the wild air? -- Ralph Waldo Emerson

Not only propane but unvented natural gas heaters will also produce a lot of water vapor.

The water vapor doesn't just condense on colder metal, it'll produce excess moisture where ever there are cooler spots with little or no air circulation, such as lower walls behind cabinets or other obstructions to air current circulation.

Some forced air flow will greatly improve currents in an entire space. I prefer to use something like a small table-top air filtration unit with a squirrel cage blower in it, pointing from one corner area toward the far/diagonal corner area.

One can improvise filters from cut-to-size filter kits instead of buying expensive made to fit brand name filters.. and I've added a grille that stands off from the front/intake grille, and cover the grille with painter/refinisher's tack cloth (sticky rosin treated cheesecloth) to catch most of the airborne dust before it reaches the internal filters, so easier maintenance and fewer filter replacements.

Forced circulation prevents a lot of problems associated with stratification of the air in a closed space when it's unoccupied. No worries about wasted energy, as the small blower motor's heat (maybe 20-50W) just adds to the room temp.

I agree that a small portable, radiant electric heater is very effective for a spot heater when needed. The designs with elements in straight quartz tubes and a polished reflector to direct the pattern of the infrared heat, are very practical, IMO.

Yeah I probably shouldn't have written it the way I did and I should have said something like "cast iron and metals, glass, any colder surface" but pretty sure that by simply saying "cast iron" I got across the basic message in terms that are understandable by most laymen.

But but...

Moisture in..... stands off from the front/intake grille, and cover the grille with

Fine if you're going to maintain something resembling some sort of constant temperaturem say ten degrees or so.....

The real problem is that upon increasing overall mean ambient temp by any significant amount , the metal surfaces will absorb heat more slowly and so basically that is where most of the moisture will tend to precipitate.

Yep, definitely caulk all seams, unfinished joints or penetrations of the interior surfaces. Caulking is the most cost effective energy reducing product that any DIY type can use. The return on the investment can be huge when applied every where it's needed. If your eardrums pop when you open/close doors, ya done real good. That doesn't mean you'll suffocate if you spend too much time in that space, as long as a group isn't cooped up in there to evade the cullers/zombies.

It will be advantageous to start caulking during the framing stages and follow-up with the semi-finished interior and/or added as the finishing is being completed.

Losing (paid for) heated air and having it replaced with cold air is where massive amounts of heating (and visey-versey cooling) energy is often wasted.

" snipped-for-privacy@krl.org" fired this volley in news:adde6a4c- snipped-for-privacy@e2g2000vbb.googlegroups.com:

Don, if the intent is to use them as dehumidifiers, then there's no need to heat or cool either space... heat and cool the same space (resulting in net heating), and run the collected water outside. (I use a 14KBTU unit as a high-volume dehumidifier AND heater for a large chemical drying room).

LLoyd

This only applies to *unvented* gaseous fueled heaters, there are plenty of vented options available. Look for a salvage RV furnace, these run on propane and are fully vented with external exhaust and combustion air. Given the better insulation one unit should have no problem heating the space. The larger mobile home wall furnaces would also work.

foot ceiling fully insulated.

All surfaces are 1/2" oriented strand board, along with a couple of double insulated windows looking into the bigger shop.

There is 4" insulation in walls and 6" in ceiling.

That's a LONG way from "fully insulated". Keeping the heat in is far cheaper than adding more heat.

Concrete floor with vinyl tile.

If the floor is cold, this is also a BIG loss. Ground under my house stays at 55F in winter. That would be a net gain for a 50F space. If yours is colder, could be a BIG loss.

Power available for heating would

be either electricity or propane.

temperatures average around 36-38°F through

the winter months. I don't require a warmer temperature for working. Can always place a small propane heater

next to me if I'm going to stand in one place for a long time.

Unvented propane in a tight space will have water everywhere. Everything will rust and mold will run wild. Lower humidity is better than warmer temperature.

four-lamp fluorescent lights.

You are right, but my thought was to use them as heat pumps.

Dan

-Finishing up framing a 13'x36' shop area within my large shop. Walls and 8 foot ceiling fully insulated. All surfaces are 1/2" -oriented strand board, along with a couple of double insulated windows looking into the bigger shop. There is 4" insulation in walls -and 6" in ceiling. Concrete floor with vinyl tile. Power available for heating would be either electricity or propane.

-Would like to maintain 50°F to keep machinery from rusting. Outside temperatures average around 36-38°F through the winter -months. I don't require a warmer temperature for working. Can always place a small propane heater next to me if I'm going to -stand in one place for a long time.

-All suggestions greatly appreciated. BTW, ceiling will have 8 four-foot four-lamp fluorescent lights.

-Thanks, Ivan Vegvary

My house with 1970 electric heat insulation does that now. It has a polyetylene vapor barrier under the sheetrock, an extra layer of attic and north-side wall insulation I added, and tightly sealed doors and windows upstairs. I left the basement as is to leak in fresh air for the stove, which isn't needed if the daytime high reaches ~ 40F. Right now four indoor humidity sensors (grouped together for testing) read 48%, 51%, 54% and 57%. The temperature readouts match better, the three Oregon Scientifics are within 0.1 degree F and the old Radio Shack is 0.7F lower.

If you can justify it a small non-self-defrosting refrigerator would add maybe 100W of heat and somewhat decrease the humidity if the door leaks a little.

jsw

The (presumably uninsulated) concrete floor extending into the unheated area (and likely straight to the outside at the edges) is going to move a lot of heat (or $) over time.

Nearly all replies have assumed (probably on the basis of "place a small propane heater next to me") unvented propane, which is a terrible idea. Use a portable electric in that case. Sealed combustion (aka sealed burner - pipe brings in outside air, pipe takes out exhaust gas, inside air never meets the flame) propane heat is probably (check local price for propane and electricity) more cost-effective than straight electric resistance heat. Depending what your lows are, and how long you have them for, a heat pump might be more cost-effective than propane, if you get a good one (high COP) and it does not have to turn into a straight electric resistance heater too often due to the outside temp being too low for it work as a heat pump.

The mini-split systems offer heat pump and A/C on a small and affordable scale...

You may also want to get an air-air heat exchanger so you can have some ventilation without wasting too much heat.

The "British-units" (more US-units these days) analysis (rounded up)

13x36 ceiling, 6" R19 (optimistic - the insulation is, the framing isn't) 468 square feet, divide by 19 = 25 BTU/hr/degF

13x36 floor, R1 or so to ground which is a bit warmer than air. R hard to figure sideways to cold shop and to exterior air, but not good.

468 square feet, divide by 1 = 468 BTU/hr/degF

13x8x2 wall, R11, (optimistic)

208 square feet divide by 11 = 19 BTU/hr/degF

36x8x2 wall R11 (optimistic)

576 square feet, divide by 11 = 53 BTU/hr/degF

Subtract square footage of windows/doors from walls, figure those at R3 if they are decent, R1 or 2 if they are not decent.

Ignoring windows/doors and the optimism of ignoring framing: 97 BTU/hr/degF for the walls and ceiling

468 BTU/hr/degF for the floor.

For 50F shop at 36F exterior, the top only consumes 1358 BTU/hr. Not really true - those R3 (at best) windows and door will eat (comarative to thier size) a lot of heat. Say you have 8 square feet of window and a

7x3 or 21 sq foot door - that adds 10 BTU/hr/degF or 140 BTU/hr - or 3 times that for poor windows and an interior-type door - to your load. And floor, even assuming a 40F ground temp eats 4680 BTU/hr - or 2340 if you call the ground 45F (and neither is accounting for the hard-to-figure but significant effect of heating the surrounding shop and air by conduction through the slab.)

If you fudged that (rounding up to account for some of the unknowns) you might call it 7000 BTU/hr at the low end of a good fudge - to get 14 degrees above outside ambient with no air exchange. If you want to maintain 50 degrees, rather than 14 degrees above exterior you'll need more heat (the average should give you a cost idea for the whole winter, the min temp is needed for "how big should the heater be to keep 50F on the worst day" and you get the average back by it turning off part of the time on warmer days with the thermostat.)

Add in air exchange - 3744 cubic feet divide by 13.9 to get pounds of air, multiply by specific heat of air (0.24) to get 65 BTU/hr/DegF for 1 air change per hour, then cut that down by how good you think you sealed it or multiply by how much ventilation to need to carry off smoke, and cut down by the efficiency your air-to-air heat exchange claims if using one. 910 BTU/hr for a 14F differential and 1ACH (normal construction.) Really tight construction can get down to 0.1 ACH, but can also be too tight to live with (not enough ventilation, unless forced ventilation with or without an air-to-air heat exchanger is used.)

Call it (average) 8000 BTU/hour (still optimistic, but..) which is an average of 2.35 KW/hr or 5640KW for 100 days (gets from now to early April) - $846 at my price of 15 cents per KWh.

For a heat pump, divide by the COP - 3 is typical - $282 - but for any time the outside temp is below the heat pump's operating range, you can't do that, so it may be more (or a lot more, as that when it's cold and you need more heat then.)

For propane, 92.5 KBTU/gallon * efficiency of furnace (less than 1 - 0.8 typical, 0.93 expensive) 260 gallons for 100 days with 80% efficient furnace, what's your price per gallon?

These are almost certainly "inaccurate in practice" numbers, but they are accurate enough for the purposes of comparison and rough guesstimation of the cost of operation. The cheapest installed cost is usually electric resistance heat, but it's generally the most expensive to run.

Per this estimate, at 15cents/KWh and with an 80% efficient propane burner, $3.25/gallon is the breakeven between resistance heat and propane. If it's near that, the lack of fuel and open flame may favor resistance heat anyway. Burning down the shop sucks.

From what I recall of m> I was paging through a woodworking book last night and the author had

Pick the right ballast and it's easily done with 240 - and presumably one phase of the 3-phase, too. Don't know that I'd like that, though - I would want the light when the machine was not yet running and after it shut off, but that's me. Just put a light switch there by the machine for that light...

Thanks Ecnerwal, what a thoughtful reply!

I will use your data analysis (adjusted for window and door sizes) and make= an appropriate decision. =20

BTW, right now I'm paying $2.48/gallon for propane. House electrical rate is $0.11/KWH Shop electrical rate is $0.32/KWH

Shop rate is high because of low usage. My last bill was $24.55 most of wh= ich was for Basic standby ($16) taxes etc. House bill was $84 for the mont= h of October. I can't combine the two for a lower rate since I enjoy the 3= phase power delivered to the shop. I suppose I could run the shop power b= ack up to the house and get a combined single bill saving me about $18 per = month.

Thanks again for all of your effort to help me!!

Ivan Vegvary

Except what the op had said was:

"Can always place a small propane heater next to me"

If you would read the original post before opening your pie hole then next time you might not look like such a goddamned fool.

I didn't do as much work as you might think - I have all of this worked out for my shop, with all the handy "secret" numbers I got from Ag Engineering's aquaculture course way back when. After that it's just a few calculations and the "deep mystery" is revealed to be math. It's handy for seeing things such as: foam floor mats or plywood over styrofoam covering most of the floor would make a lot more difference in your heat loss than a better door or an inch or two more insulation in the walls.

Service charge is the price of being connected at all, and is best (mostly) ignored when looking at cost of power for heat (which will certainly up your useage.) Some months I have 0 KWH, which would make the price of power infinite for those months...it's just overhead, and the price of each KWh used is what it is, unless I'm going to disconnect the power to avoid the overhead (not likely.)

If you would get down to 11c/KWH at the shop by burning more, (or it's

10c plus service charge, or whatever) then electric is cheaper for you. Roughly equivalent to $2.39/gallon propane with an 80% efficient furnace.

Check with the power company before doing anything about feeding the house from the shop - they may not let you. In any case it may cost more to do than it's worth in savings - but look at that cost if they would let you.

One thought (not my idea, swiped from here in the past) is to put (bond, ideally) 50W-200W heaters in/on/under the all the cast iron tool bases. If you leave those on all winter, you can be assured of no condensation on the tools (put one in/on/under any tool cabinet as well) while using less overall power, and just crank the heat up to 50 (or more) when you are actually working.

temperatures average around 36-38°F through the winter months. I don't require a warmer temperature for working.

I live in the officially wettest town in Canada. The temps are about the same as yours. I have had no heating in the shop for 5 years and so far no rusting of note.

Are you sure you will not make things worse? You will need to maintain the temperature of the air and the surfaces steady 24/7 otherwise you are risking condensation with consequences.

Michael Koblic, Campbell River, BC

Must suck, to have people like me on the list.

Christopher A. Young Learn more about Jesus

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If you would read the original post before opening your pie hole then next time you might not look like such a goddamned fool.