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Discussion Starter #1
We are having a 32'by 28' garage built and I'm going to have the walls and underside of the roof spray foamed and the garage doors are going to be insulated. An LP gas line is plumbed to bring into the building. The roof framing is trusses and I wasn't going to have ceiling drywall installed, just open trusses. Might keep the garage a bit cooler in the summer.

My plan was a hanging forced air LP heater but looking over the crop of hanging heaters I have no idea of which one to choose. Any recommendations? Should I consider an LP radiant heater instead of forced air? Would one be enough (it's a three bay garage.)

Usually we get into the low teens and even single digits very occasionally, the objective it to just keep the garage in the ~55 degree range.
 
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With proper roof and soffit ventilation wouldn’t enclosing the ‘attic’ space, and insulating it actually keep the interior space cooler than not?
 
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You first need to calculate the amount of BTU’s you need. There are free online calculators to do this.

From there you can choose your heating equipment. For a large open area I would think that fan forced unit heaters would be better than radiant heaters - they heat a smaller space more directly.

Heating BTU Calculator Heaters by BTU
 

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I swear by my MrHeater in our small shop. I bought the 45K BTU. It's a little undersized for the space and runs a little longer. I was afraid the bigger one would short cycle and not last as long.

When first bought it the motherboard went out. They next dayed one to me no problem, did care how long I owned. That was refreshing.:bigthumb:
 

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I've walked that path... 30x40 spray foam walls & ceiling. Had no electricity so I went with radiant propane hanging above my tractor so it was always thawed out & dry. Only kept garage 40-50 degrees. Well, spray foam seals things too good to get by without a vented furnace. walls sweated, windows frosted etc. I've got a like new Mr Heater radiant I will sell you, but trust me, you don't want it.
Last year I got power in shop & hung a nat gas furnace and WOW, what a difference!
I strongly advise a vented heating device. Learn from my mistake please.
 

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Discussion Starter #6
With proper roof and soffit ventilation wouldn’t enclosing the ‘attic’ space, and insulating it actually keep the interior space cooler than not?
Building science has moved on from the traditional ceiling drywall with batts or blown in insulation (and attic ventilation.) The 1500 sq ft house addition we added last year has spray foamed roof rafters - about five or six inches of open cell foam and no ceiling insulation and no soffit ventilation. Now we have conditioned walk in attic space, its temperature is only five or six degrees warmer (or cooler when heating.) The HVAC ducting doesn't get super heated in the summer or super cold in the winter. The entire house (exterior) is now spray foamed and even the interior walls in the addition. Our bedroom is as quiet as a church on a Monday morning :good2: .

Check out this builder's YouTube channel. He stays on top of the latest and greatest (but he's very discriminating - he's not pushing products, if something is junk, he will say so.)

Going to be interesting trying to figure out BTU requirements with no ceiling and the garage doors but that's a good idea, I'll give it a shot. And thanks for the Mr. Heater recommendation - with a name like that, how can you go wrong!
 

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Discussion Starter #7
I've walked that path... 30x40 spray foam walls & ceiling. Had no electricity so I went with radiant propane hanging above my tractor so it was always thawed out & dry. Only kept garage 40-50 degrees. Well, spray foam seals things too good to get by without a vented furnace. walls sweated, windows frosted etc. I've got a like new Mr Heater radiant I will sell you, but trust me, you don't want it.
Last year I got power in shop & hung a nat gas furnace and WOW, what a difference!
I strongly advise a vented heating device. Learn from my mistake please.
We were typing at the same time, missed this. Yes, I'm somewhat familiar with a non-ducted gas furnace and humidity/condensation - been there done that before our total house remodeling last year. We still have that LP 'fireplace' but it's only for emergency heating if we lose power in the winter.

Do you know what kind of spray foam you had - was it open cell or closed cell? Open cell foam will breathe but closed cell foam will not, it makes a difference.
 
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My garage is 28x30 and I got one of those forced air heaters that hangs in the corner, sound like what you are looking at. I'm not sure what one to recommend, there are so many. I keep my garage at about 45 degrees and it will heat it up in just a few minutes to about 65. Mine is LP also and I probably heat that space for about $100 a year.
 

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What is your ceiling height? That and distance from the ceiling to equipment may impact radiant. You want a few feet of clearance.

IR radiant heat can be more efficient like the in floor heat system I went with compared to forced air. Notice I said can be. There are disadvantages to the radiant options. That is the use case where one might want to work in a garage space for the evening once in a while or for the weekend once in a while and the times they are not out there, don't feel the need to maintain 60F or so temps. The problem with the radiant options is they are much slower to react to a call for a change in temp. For instance if I want to go from 40F to 60F in my garage with in floor heat, I expect that to take a day or two in order to get to temp. In comparison, I have a NG forced air hanging heater in the pole barn/workshop that maintains 34-36F all winter. If I need to do an oil change or something out there some evening, I get home, I walk over to the thermostat and slide it up to 60F. By the time I go in get changed from work clothes to get stuff done clothes and get back out there, it is getting warm. If I am out there for a weekend I can get it to temp and maintain that temp quite quickly. Granted the slab is really cold so my feet get cold but I also wear insulated boots to combat this.

Based on that it sounds like forced air is the best, it is when you want to use it in that manner where there are shorter term uses. Up north you may not want to keep it that warm and are just looking for warm enough to melt off the snow. Keeping it at 60F is very expensive. As soon as you open a garage door you lose all the heat you built up and the furnace has to start over. Even if you maintain 60F, the slab will be warmer but not like with radiant (at least in floor). It might be 60F but more likely it would be closer to 50F if you maintained 60F air temp. Heat rises which is the problem. In the case of my in floor system, I am pumping in glycol at roughly 110F and it is coming back at around 100F. That is maintaining 60F in the garage. That means my slab is around 100F. Walking on it, you can feel the heat through your shoes. IR radiant tubes will heat objects in the same way. However it is limited to line of sight. Meaning if you park a trailer under it, it will heat the trailer more than the slab. It is better to heat the slab because if you open the garage and take the trailer out, the slab where shaded from the IR heat will be colder. By maintaining heat in a slab what I have found is it can be in the 20F range which we have had some mornings here already. I can open the garage doors to pull a vehicle in or out and the heat rushes out. However I close the door and go back in the garage. Within a couple minutes it is back to 60F. Another benefit by heating objects like that is they are warmer to the touch as well as the fact that you are heating the lower part of the garage. Unless you spend most of your time on stilts or on a ladder, who cares if it is a comfortable temp 12' in the air. I am not up there very often. Forced air systems have to heat from the top down. So if you go with one, I would also consider a fan or a few of them of some sort to help push that heat down from the ceiling. I have added fan boxes for my build but I don't really plan on using them much in the winter.

Bottom line there are pros and cons for the different systems. There are a lot of people out there that love their radiant systems and others that because of their use case, find that they were a waste of money and they go back to a forced air system.

Also you didn't mention it but here is another thought. You are in TX and it isn't that cold. What do you have for power out there? Have you considered a heat pump? The benefit is that the single unit can not only provide heat for your space but also AC. Just a thought for you. They work fine for heat, maybe more expensive but some power companies allow a price break for power used for heat. They work OK in our area but when temps get really cold. Like -20 or -30F they really don't work well. You are not going to see temps that cold. Really where they start to struggle is around that 0F range. That is unless you go full Geothermal system with a heat pump.
 

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Discussion Starter #10
Thanks very much for helping me in my quest sennister :hi:

You guys up there in the Minnesota tundra have way different heat requirements than us in more temperate zones. A relative has a second home in Colorado at 9,000' elevation and it has heated floors, absolutely love that (we spent a week there watching it snow a few years ago.)

I think I have my dilemma figured out. Thanks to the Dr's advice about using vented vs. non-vented I found a forced air vented on a search and talked to the business about my requirements which took into account my location, building size, etc. She said 45k BTU would work well, the calculated BTU need was just under 30k.

So I found this one (100$ cheaper than the first place) and they have a horizontal duct kit which will eliminate the need for a roof penetration.

And the heater is made in the USA, I like that.
 

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Wouldn't a mini-split system work good in Texas? Then you'd have AC and well as heat.
 

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Thanks very much for helping me in my quest sennister :hi:

You guys up there in the Minnesota tundra have way different heat requirements than us in more temperate zones. A relative has a second home in Colorado at 9,000' elevation and it has heated floors, absolutely love that (we spent a week there watching it snow a few years ago.)

I think I have my dilemma figured out. Thanks to the Dr's advice about using vented vs. non-vented I found a forced air vented on a search and talked to the business about my requirements which took into account my location, building size, etc. She said 45k BTU would work well, the calculated BTU need was just under 30k.

So I found this one (100$ cheaper than the first place) and they have a horizontal duct kit which will eliminate the need for a roof penetration.

And the heater is made in the USA, I like that.
I was trying to be a little careful in my post to avoid the reply "well you know it does snow it Texas". As I am aware that it does happen.

That said, yes our needs are a little more on the extreme side. In Texas, a forced air system probably doesn't have all the the same disadvantages that we face up here, or at least they are not as big of a deal. The main points are that you want to fully understand that while radiant is great, there are some drawbacks. Then main being where you want more temporary heat or a quick change in heat. Getting back to not knowing your climate as well, but I could see cases where you might want heat and by the time a radiant system could actually heat the space, you might find that the cold front has since moved on and you don't need the heat anymore. Then you would find yourself constantly having to watch the forecast to stay ahead of something or always playing catch up.


Wouldn't a mini-split system work good in Texas? Then you'd have AC and well as heat.
I agree, he didn't have it on his list but as I mentioned at the end of my previous post, I was wondering if he has considered a heat pump or as you call it a mini-spit. As you mentioned the big benefit is that the AC side of a system like that might be more advantageous than the heating aspect. It would work like a forced air system just electric rather than gas. Not sure about electric rates and such.

We are actually considering adding one to our garage build and I have done some work to make it easier to add later. I want to see how expensive it is to heat my space at a straight 60F all winter. Or at least as we get into the really cold parts and do some comparisons to some cooler temps. How much less is it to keep it at 50F or 40F which is the lowest the system will go. I could use a mini-split to get the temp up for a short duration use like where I want to go out for the evening. Though I could also do that with a water to air heat exchanger like what I am adding to the pole barn. The benefit of the mini-split is as you mentioned, AC on hot summer days. While the mini-split won't work well when -30F out, it also isn't like that all winter and normally it is just a cold snap for a few days. Closer to 0F is more common for most of the winter and they work then.
 
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Oh one other thing to consider. Some of these high efficiency furnaces, boilers and other types of heaters do have condensation. The furnace in our house, our tankless water heater in the house and now the boiler we added to the radiant heat system all have condensation that we have to deal with. In the case of the new garage, we ran what will be a drain pipe that will tie into the septic system. I don't have it doing that yet because I have unheated space (the mud room and future laundry) between the garage and house. Because of this I wouldn't be able to pass a plumbing inspection. However I can install the drain pipe that runs back to my tuck under basement right next to existing pluming. For now I capped it off and put a barb fitting on the end that drains into a condensant pump. That will pump the water to a drain for the time being.

I only mention this because it may help with your heater placement if you have to deal with needing a drain of some sort. With a detached garage maybe you can route it to a floor drain of some sort or outside somehow. Just something to ask the HVAC people about if needed. I didn't think of it when we built the garage and the HVAC guy never mentioned it to me. I told him it was a future drain but he got nervous when I explained it wasn't plumbed through to the septic yet. I asked how much water I can expect and he said if it is running at 100% it won't produce much water at all. It produces at the lower power levels. From watching it, the boiler is consistently running at about 25-30% load. He said depending on humidity levels and such, we could expect up to around 5 gallons of water a day.

Like I said, ask about it, not sure if it is an issue to consider. If you don't plan for a drain and it is required your only option might be on the slab and do you want a wet floor all the time?
 
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Conroe to Navasota area of the hill country I would go with a mini split, heat & air.

The spray foam along with the type of cold in that area you should be fine with a MS especially if you slab is insulated.
 

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lot of good advice above...

instead of explaining things ...sennister has already done a good job of it...i will list my preferences if it were mine

#1.....spend money on insulation during construction..more more more...will lower your ussage and initial equipment costs and serve you well the entire life of the building

#2....a well insulated structure in TX as stated would be a great candidate for a mini-split heat pump...obviously the up front cost would be a bit more...but having AC in the summer if you have a to do service would be priceless

#3 ...a tube infrared heater would be my third option ....as sennister mentioned clearances can be a issue and should not be overlooked

#4 ...a forced air ceiling hung unit..probably the cheapest option up front since you already have gas to the building

everything vented...as a last and temporary resort would i consider a non-vented unit

per your post your going to option #4....which will serve you well seems like a good unit....dont forget my option #1 :) and i assume your source considered your insulation system when sizing the unit ?

fwiw....i have a attached workshop....24 x 40 x 15' eave with 4/12 open trusses 8" of fiberglass insulation on exterior (obviously one side is attached to living space) one single 12 x12 insulated oh door ......the shop has a seperate ground source heat pump heat/cool unit 18000btu's and it maintains temps fine in our climate SW MO year around both on the heat and the cool side .....just putting this out there as additional info
 

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Discussion Starter #16 (Edited)
Great recommendations and ideas! :bigbeer:

For those who haven't read my earlier post, the target building is 900 sq ft, 10' stud walls, spray foamed walls and under the roof, insulated doors. No ceiling.

I'm real familiar with mini-splits, I have a small cool only mini-split in my office/radio room/electronics lab. They are amazing. So amazing I paid a huge premium for two zone ducted mini-split heat pump in our 1500 sq ft addition. It struggled a bit when we had a 105F day last summer but the room temp was only about 4F above set temp. Even so impressive, they work well in our area. You literally cannot hear it running.

I had not considered a mini-split for the garage, interesting idea. I'm looking at about $1k for a forced air vented 45k BTU LP heater, a large mini-split would be at least $3.5k. Still cooling and heating the garage is tempting.

Edit - we have zero need for permits and inspections out here in the wild west, but I was reading the instructions for forced air gas heating vent ducting and they did mention a condensation drain if required by code. I thought about a floor drain but decided to just have the slab slope inboard and then out.
 

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Great recommendations and ideas! :bigbeer:

For those who haven't read my earlier post, the target building is 900 sq ft, 10' stud walls, spray foamed walls and under the roof, insulated doors. No ceiling.

I'm real familiar with mini-splits, I have a small cool only mini-split in my office/radio room/electronics lab. They are amazing. So amazing I paid a huge premium for two zone ducted mini-split heat pump in our 1500 sq ft addition. It struggled a bit when we had a 105F day last summer but the room temp was only about 4F above set temp. Even so impressive, they work well in our area. You literally cannot hear it running.

I had not considered a mini-split for the garage, interesting idea. I'm looking at about $1k for a forced air vented 45k BTU LP heater, a large mini-split would be at least $3.5k. Still cooling and heating the garage is tempting.

Edit - we have zero need for permits and inspections out here in the wild west, but I was reading the instructions for forced air gas heating vent ducting and they did mention a condensation drain if required by code. I thought about a floor drain but decided to just have the slab slope inboard and then out.
45k seems like a excessive heating load calculation for your area ...... mine is at least 50% larger cubic ft wise...well worth a real load calculation if your considering a heat pump at all
 

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TRactor Tim did a mini split kit on his old building. I think the pre done kits are much more affordable on a DiY basis.
 

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I don’t remember how big the heater is in my garage but it’s oversized. The guy that installed said the price difference was something like $30 more than a smaller one. It’s nice because it heats things up really fast. I plan on getting a portable AC unit for mine this next year. If it’s 95 outside getting it down to 80 feels pretty good. I had a window AC unit but the mud daubers built inside it and ruined it.
 

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Great recommendations and ideas! :bigbeer:

For those who haven't read my earlier post, the target building is 900 sq ft, 10' stud walls, spray foamed walls and under the roof, insulated doors. No ceiling.

I'm real familiar with mini-splits, I have a small cool only mini-split in my office/radio room/electronics lab. They are amazing. So amazing I paid a huge premium for two zone ducted mini-split heat pump in our 1500 sq ft addition. It struggled a bit when we had a 105F day last summer but the room temp was only about 4F above set temp. Even so impressive, they work well in our area. You literally cannot hear it running.

I had not considered a mini-split for the garage, interesting idea. I'm looking at about $1k for a forced air vented 45k BTU LP heater, a large mini-split would be at least $3.5k. Still cooling and heating the garage is tempting.

Edit - we have zero need for permits and inspections out here in the wild west, but I was reading the instructions for forced air gas heating vent ducting and they did mention a condensation drain if required by code. I thought about a floor drain but decided to just have the slab slope inboard and then out.
I would agree that having a ball park estimate of around $3k is probably going to be close for a mini-split. It will be more expensive for the initial purchase and maybe to run as well. It does have some advantage in terms of one investment covering both needs. Not sure how much power it will take to run. Probably depends on the system size but I would imagine 30A 240V would be common.

I remembered that you said you were doing spray foam insulation on the walls and basically what is the inside of the roof. What I don't remember you saying was if you were going to have for trusses. Maybe you were going with a storage truss where you have an attic. Maybe you are going with a standard truss and it is just open all the way up to the peak. While that is fine, I would imagine it will make it a little bit harder to heat with a forced air type system. If you had some form of ceiling, even if not well insulated, it would help keep some of that heat from just rushing up to the peak. If you look back to where I was talking about one of the disadvantages of a forced air system is that you have to heat the space from the top down. Where radiant type systems heat from the bottom up. One way to try and combat this is to install some form of ceiling fan(s) to try and force the air back down. You may want them anyhow for the hotter time of the year. Though you might want them way up in the peak or I am not sure how effective they will be.
 
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