Heating My new shop---inputs requested

[Angelfire]

Hiya Folks,
I am in the process of looking into heating for my new shop. Specs are as follows:

Size: 32x40 (exterior dimensions) ...There is a small indent into it at the porch which reduces overall SF by around 24sf.
Construction: 2x6 stud wall, trusses overhead, half of the building is 9' ceilings, the other half is 11'8" ceiling. Concrete slab. Detached from house.
Doors: 1- 16x9 roll up door, 2 3068 pedestrian doors.
Windows: 6 windows, double paned. Approx. SF of window space: ~100sf
Skylights: 4 @ 2'x4'
Insulation: Not currently in place but planning to insulate walls with R23 and the ceiling to a minimum of R45. Could go to R75 if needed although that gets more $$.
Fuel: Nat. Gas
Location: Albuquerque NM (5800' elevation, zone 4 climate)

My initial thoughts were to use a ceiling hung unit heater (similar to the Mr. Heater models). I've got one in my current garage attached to the house and it's worked great. I did a heat load calc using an online utility and came up with having a 70k BTU heat loss. The Mr. Heater type unit heaters won't keep up with that. I see Reznor makes a 100k BTU (83% eff.) unit that would work but runs about 2x the cost of a 75k BTU (80% eff) unit. I got to thinking that it might just be worthwhile to install a regular forced air unit and run some ductwork. I really don't want to get fancy here and cost is definitely at the top of the priority list. Not to mention lost floor space and the hassle of putting together the system. Another option would be to go with 2 of the smaller 45k BTU unit heaters at roughly the same cost of 1 of the Reznor 100k units. This would give me some flexibility in terms of only running one unit in cooler weather and running both units in downright cold weather. I have not done any de-rating based on altitude but know it needs to be factored in.

So I'm asking the experts out there what you'd recommend for my situation?

Thanks much.

 

[rponfick]

I have the same size and specs. of your garage, and am considering new heating unit. Will be watching comments.

Ralph.

 

[Shop Specialties]

70,000 BTU is on the high side unless the door is going to go up and down a 100x a day. With it being insulated that well I would say 50,000 BTU - 60,000 BTU would be more than adequate. I would go with 1 hanging forced air unit placed in a spot where you would get the best air movement and call it good.

 

[Angelfire]

Thank you. So far your estimate seems to align with a few others I've gotten/done. Crazily enough, I've gotten estimates from folks supposedly doing load calcs that range from 30k BTU to 78k BTU. Some ask me about altitude, some don't. I think I'm going to shoot for a 60k unit and if it just doesn't cut the mustard, then I'll add a wood stove (half of this shop will be woodworking). One person suggested I place the unit heater in a corner and aim towards the wall with the overhead door. I was planning to locate this in the lower ceiling area figuring with heat rising, it would easily fill up the higher ceiling area. It sounds like I shouldn't do that as code requires the unit to sit 8' above the floor, or so I understand it. So unless it's just not right, I will plan to install in the higher ceiling area and aim towards the wall with the garage door. Thanks for the help.

 

[Big-Foot]

I put a 100k BTU Forced Air furnace in my old shop (800 SF) and it would take it from 45 to 65 in about 15 minutes... I had it up on a couple of course of concrete blocks. Hey it was $250 and it works like a champ..
My new shop has a hanging 100k BTU and it seems to take forever to warm it up in there. I have a ceiling fan about 15' in front of it now and that helps get the heat off of the 11' ceiling...

 

[regguy1]

I have a 45K Mr Heater in a 26' x 30' R 13 walls and ceiling, heats it just fine. A 75K should be plenty for your size building;

Check it out here: http://www.garagejournal.com/forum/showthread.php?t=140674

 

[dave67fd]

Agreed,
With your insulation specs the 75k unit will be plenty. Remember the heater ratings are input so they put out less. A 75k unit will put out around 60k BTU's.

The heater should also face or blow to the coolest area. That would probably be your overhead doors.

 

[Angelfire]

Thanks folks for the inputs. It's amazing that something like a load calc can be done so many different ways by companies selling furnaces. As an example, Sterling recommended a 105K BTU heater, Reznor recommended a 45K BTU heater, and Modine recommended a 90k BTU heater. Crazy. My own load calc's done with some online free calculators, which may or may not be all that accurate, show me with a 42.6K loss when figuring a 60 degree rise. So I think I'll go with the 75k unit considering efficiency and altitude loss will bring the effective output down to around 45k BTU.

All this being said, I haven't done my due diligence at fully designing the layout of my shop yet. Just too much on the plate but in the back of my mind, I've got a thought of putting a wall up down the center to separate my woodworking from my automotive/welding endeavors. This would then put me in a position to be needing two smaller units, one for each location. Probably 45k BTU's in each.....that gets expensive for the equipment but would allow me to heat just the area I'm working in so maybe it would work out in the end. Need to run some calcs to see.

Thanks much for all the help!
cc

 

[BadgerBoilerMN]

Heat loads can be done many ways, but only one is right. 75mbtuh is outrageous. Forced air unit heaters are the absolute bottom of the comfort/economy scale for heating any warehouse, garage, etc.

You are in the land of radiant floor heating; the ultimate in comfort, easily zoned, no open flame, silent, dust-free, efficient and eternal (the PEX tubing in the slab will never wear out.

If you are in Albuquerque proper, you have cheap, clean natural gas and could use the ultimate radiant floor heat source, a condensing boiler.

 

[Angelfire]

My understanding of how radiant works doesn't really work with how I work. I typically may go days without doing anything in the garage and then jump into something for a few days. With radiant, my understanding, is turn it on and wait a good while before it warms the space. I wouldn't get much out of that. Additionally, I don't have water to the garage and the slab's already poured. So radiant is definitely out.

 

[Notch1988]

What about overhead tube radiant? I had an 80k BTU radiant tube in my last shop (24x40x12) and loved it. I kept the garage at 40 and it would get to 60 very quickly and this is with steady -20 weather.

 

[Rickcnc]

What about overhead tube radiant? I had an 80k BTU radiant tube in my last shop (24x40x12) and loved it. I kept the garage at 40 and it would get to 60 very quickly and this is with steady -20 weather.

Just curious what was your yearly operating cost

 

[BadgerBoilerMN]

Infrared is for those who poured the slab to quick. We do it all the time. It is infinitely more efficient, comfortable and can be all but sealed combustion. Two stage units are the most efficient and comfortable.

But, unit heaters are definitely cheaper up front.

Radiant floors are not necessarily slow to respond. If your projects run for a few days, radiant floor would have been perfect. In mild climates like most of NM, radiant can't be beat.

 

[Angelfire]

I'll have to look into the infrared stuff as well as tube heaters. I really don't want to lose much ceiling space so that may be a factor. And regarding the in slab radiant heating, I know more people here that have it and hate it vs those that like it. To each their own I guess.

 

[regguy1]

Remember, infared tends to heat objects and not air.
I can go into my garage and turn the T Stat to 60 (from 40) and in 15 minutes it's toasty in there.

 

[Angelfire]

Ok. Infrared Tube heaters are definitely out. Too much clearance requirements particularly underneath them and they cause havoc with woodworking (ie. warped wood, uneven drying of wood, etc...) according to a number of folks over at Fine Woodworking. So at this point, I'm back to unit heaters. Just need to bottom out on my load calc.
Thanks folks.

 

[regguy1]

If you're into woodworking you should consider the models that take combustion air from outside, I believe Modine and Reznor have them. Mr. Heater does not.

Here's Reznor sealed combustion models: http://www.djsonline.com/reznor_UDAS_Separated_Combustion_Unit_Heaters.htm

Modine, scroll down for sealed combustion models: http://www.djsonline.com/modineunitheaters.htm

Mr. Heater: http://www.djsonline.com/mrheater_garageheaters.htm

 

[Angelfire]

Thanks Regguy. I was looking at the separate combustion models already...specifically the ones from Sterling as they appear to be significantly cheaper than the Modine/Reznor/Etc... versions. Of course, they nail you to wall for their vent kit so it probably all works out to be the same in the end. I will have full dust collection in place eventually but even so, I'm sure the heater will see dust and well, the fumes from vehicles parked inside and finishing work etc...it just makes sense to go with separate combustion.
Cheers,
cc

 

[Steevo]

My shop, located in Eastern Idaho, is 24x40, has 12' ceilings, 2x6 stud walls, truss roof.
Entire interior is done in 5\8" finished sheet rock. Walls are insulated with R21 un-faced batts. Ceiling has 18" of blown-in cellulose insulation (R60+).

I have a Mr Heater 75k ceiling-hung unit heater, and keep the thermostat set to 50 degrees all the time. When doors are not opening or closing, it only cycles a few times a day even when it is well below freezing outside. If I open a door for a while, say to move vehicles in or out, etc., it will warm back up and shut off in less than 15 minutes.

 

[theoldwizard1]

You mention "fine" woodworking. Is reasonably constant humidity an issue ?


Question for the pros: Do you need to change orifices for high altitude installations ?

 

[BadgerBoilerMN]

Both infrared - sometimes incorrectly referred to as "tube heaters" - and radiant floor heating systems must be designed and installed correctly. Two years ago we designed and installed an infrared for a cabinet maker. He seems happy, but must be ignorant of all the warping, uneven drying and such.

If you know anyone whom is unhappy with a properly designed and installed radiant floor woodworking shop, please refer them to me. We have done hundreds and have zero complaints...isn't that odd?

By the way, in clearance on low output two stage infrared models is one foot from wall and ceiling.

But plain old scorched-air wind blowing, open flame unit heaters are cheaper and heat loads don't matter much if you don't care about the rest.

Theo;

Orifice size is for the trained professional, but all atmospheric and some sealed-combustion, direct-vent gas-fired equipment is de-rated for altitude. Not much humidity to worry about the three years I live in Albuquerque.

Now these are good questions...

 

[Angelfire]

My shop, located in Eastern Idaho, is 24x40, has 12' ceilings, 2x6 stud walls, truss roof.
Entire interior is done in 5\8" finished sheet rock. Walls are insulated with R21 un-faced batts. Ceiling has 18" of blown-in cellulose insulation (R60+).

I have a Mr Heater 75k ceiling-hung unit heater, and keep the thermostat set to 50 degrees all the time. When doors are not opening or closing, it only cycles a few times a day even when it is well below freezing outside. If I open a door for a while, say to move vehicles in or out, etc., it will warm back up and shut off in less than 15 minutes.

Thanks Steve. Mind if I ask what you have in the way of windows, doors, and what altitude you're at?

 

[Angelfire]

You mention "fine" woodworking. Is reasonably constant humidity an issue ?


Question for the pros: Do you need to change orifices for high altitude installations ?

Shouldn't be unless the rh is always very high. We have pretty dry conditions here so I've not had to worry much about it to be honest. What really causes the issues is changing humidity.

 

[Angelfire]

Both infrared - sometimes incorrectly referred to as "tube heaters" - and radiant floor heating systems must be designed and installed correctly. Two years ago we designed and installed an infrared for a cabinet maker. He seems happy, but must be ignorant of all the warping, uneven drying and such.

If you know anyone whom is unhappy with a properly designed and installed radiant floor woodworking shop, please refer them to me. We have done hundreds and have zero complaints...isn't that odd?

By the way, in clearance on low output two stage infrared models is one foot from wall and ceiling.

But plain old scorched-air wind blowing, open flame unit heaters are cheaper and heat loads don't matter much if you don't care about the rest.

Theo;

Orifice size is for the trained professional, but all atmospheric and some sealed-combustion, direct-vent gas-fired equipment is de-rated for altitude. Not much humidity to worry about the three years I live in Albuquerque.

Now these are good questions...

No need to get snarky now. Just relaying what I read on a few posts at another specialized forum. As for your cabinet maker, I've not known many that keep wood in their shop for more than a few days. Myself, it may take weeks to build something so exposure to the radiant could be much more detrimental, or not.

I'm sure radiant will save the world but I just don't think it's going to work for me. You mentioned clearances but didn't mention the clearances below the tubes. From what I have seen, it appears to be around 5-7 ft depending on the units size etc....that's a lot of real estate to give up should I put it up in my 9' ceiling area. If I put it up in the 12' area it would work except at some point I plan to add a lift so the last thing I'd want is to violate clearances with a vehicle on the lift. I've painted one vehicle in my life and would rather not do it again.

Now in fairness, am I looking at the wrong products? Is there something out there you are thinking of that doesn't require significant clearances under the tubes?

 

[Steevo]

Thanks Steve. Mind if I ask what you have in the way of windows, doors, and what altitude you're at?

Five windows, each 15" wide by 40" high, double-pane.
Two overhead doors, both insulated, one is 10'x10' and one is 6'x8'

Altitude is about 4700'

 

[Angelfire]

Five windows, each 15" wide by 40" high, double-pane.
Two overhead doors, both insulated, one is 10'x10' and one is 6'x8'

Altitude is about 4700'

Thanks Steve. We're actually not that different in terms of size, losses, etc... and altitude is pretty close as well. This helps in terms of validating the number of load calc's I've done as well as those done by others. Thanks much.

 

[mrpowderkeg]

I will have a good comparison once I get my shop done, as to radiant vs forced air. My friend built a shop slab on grade, insulated under the slab radiant heat, 2x6 walls, 36x40 12 foot walls. Mine is 32x44, with 2x6 walls, on a real foundation, I will be using a home furnace, it will allow for central AC for the summer. I will supplement with ceiling fans to get the hot air down. It should be a good comparison. Both are natural gas.

 

[BadgerBoilerMN]

Snarky is my middle name .

I typically use one tube a foot from outside and ceiling one side of the room placed at a 45° angle.

Ceiling fans can cool you off by increasing evaporation and moving warm air around the body. They do the same thing in winter. You will be hard pressed to find a fan company that has a spec for ceilings below 10' since the fuel saving do not exist.

You might consider radiant ceilings or European style panel radiators with a swamp cooler for better humidity control. Naturally a energy recovery ventilator should be considered as most steel buildings built today are too tight for human habitation.

 

[Angelfire]

Aren't there clearances to be maintained below the tube as well? I haven't done a ton of research but what little I have looked at, show clearances of 5-7' below the tube. It would seem that this would knock out putting anything combustible against the wall where the tube is hung (depending on ceiling height of course).

Regarding ceiling fans etc...you lost me there...I wasn't sure where those came into the conversation...that being said, I will install a couple of them down the road.

Radiant ceilings or Euro radiant panels sound expensive!

 

[BillK]

Angel,
Something else that has not been mentioned, but should sway your decision, is whether you may want to put in AC in the future. I would think your area gets pretty toasty in the summer and it would be nice. I think I hate working in the heat and humidity more so than the cold.

If you think you might want AC, I would think a "home" style condensing furnace with some simple duct work would be the lick. That way you could either install AC when you build it, or in the future. I am sure the heat loss in that building is a lot more than my house, but my house is 2100 sq ft split level built in 1978 and since we installed the Carrier 90% or so condensing type furnace, my gas bill has never been more than $110 and that includes hot water.

Hope this helps,

 

[Angelfire]

Thanks Bill. Yes that is definitely a consideration.

In the back of my mind I figure if I did a unit heater, I'd probably look at a mini-split type system if I decided to ever cool the place. I've not researched enough to know how they work for a space my size but it's definitely in the back of my mind to go with a full furnace/AC setup. I'm mostly trying to size my gas line at the moment so have been researching the heating load etc... of it so far.

 

[BadgerBoilerMN]

A mini-split is certainly the answer if you can afford it. It will heat, cool and dehumidify better than most technologies in most climates. Sizing is still an issue.

Humidity is not in Albuquerque unless you are creating it, in which case an ERV is the thing.

No stacking wood under the infrared.

Any forced air unit will have to have a Merv filter and regular maintenance.
The mini-split will also need extra attention though the open flame issue is mute.

Fans were mentioned by others and often misapplied...just noting.