Overwhelmed with heating design

[Woody325]

I'm just under roof with my new garage, and have picked back up the research for a heating option, but man oh man! - the more I read and research the more confused I get. Now I remember why I shelved the heater research several months ago ...

I was looking for the easy button, but that doesn't seem to exist, so I have some stupid questions that hopefully the collective can help me with to point me in the right direction.

My garage specs are:
- 24'x36' detached garage with hip roof and 2.5' overhang. 3 separate doors
- Inside ceiling height is 9'6" and the eaves are ~8" lower than the ceiling.
- Natural gas line plumbed in, and located in Pittsburgh.
- The underside of the roof deck and walls will have closed cell spray foam insulation.

I don't expect to keep the garage at 70°, but just want to keep it at or above 40-45° so nothing freezes, and turn up the heat while I'm working in it.

Stupid questions;

1. I was hoping to keep the rafters (truss) open for storage, and wasn't planning to finish with drywall. Is a drywall ceiling required in order to use a vented type heater (Hot Dawg, Big Mazz, Reznor, etc.) for a detach garage?

2. I prefer not to have to vent through the roof, but I can't figure out how to side vent with 2.5' overhangs and a hip roof (no gable end). Does the side vent need to run 3' below the eave if it's going to extend 6" past it? What is that minimum vertical distance from the eave if extending 6" beyond? If still 3' then side venting isn't an option because the vent pipe would need to exit at ~5' height (which is a problem both inside and outside)

3. What about a ventless radiant type heater (like Dyna-glo) - I haven't seen a lot of posts/information here about that as an option? They're comparatively inexpensive and simple to install, but can they be controlled via thermostat? There has to be a drawback that I'm missing.

Thanks in advance for any input and advice. Looking forward to any discussion to help me get educated and simplify what seems to be overwhelmingly confusing right now.

 

[Mainiac Mat]

Based on your point #1, it sounds like you're not planning on insulating the garage ceiling.

Seems kinda silly to heat an uninsulated space, as you'll more or less be dumping BTUs into the atmosphere (especially if your eaves are vented). You're also likely to have issues with melted snow freezing up when it dribbles down the roof to the cold overhang.

If you only plan on working out there occasionally during the winter months, just get a torpedo heater and call it good.

 

[Woody325]

Thanks Mat the Maniac,

To clarify - it is insulated space. The closed cell will be sprayed directly to the bottom of the 4/12 roof deck and eaves aren't vented (insulation is blocked at wall). I've done this on an existing addition and it works beautifully with no issues of freezing at overhang either.

So back to the heating question - torpedo is what I'm using to paint, and work in there now, but as I stated earlier I want a thermostat-controlled solution that will keep the garage above freezing when I'm not working.

The biggest question I have at this point is with regards to the horizontal venting. Can I come out of the wall, say at ~6" below the eave/overhang, and extend to 6" beyond the roof?

 

[sz0k30]

Just get a radiant tube heater.

 

[PWC Repair]

Sounds like a great place for a dual head mini-split.

 

[Woody325]

Radiant tube is an interesting idea. The mini-split seems to be overkill as I don't need the AC part of it, and the cost seems to be higher than other heating options.

I need to read up some more on the radiant tube solution. I know they're used in warehouses and shops so it seems like a good solution ? Probably more efficient for garage doors opening and closing (?) over forced air. I imagine a car directly under it getting too toasty though?

 

[toyotadriver]

Don’t be afraid of venting out the roof. If done right it will never leak.

I have a 30x40x10 shop and have open rafters. I also heat it with a vented Mr Heater Big Maxx 80k. The roof is insulated with rigid foam sheets (3 inches worth). The Mr Heater is awesome. A ceiling fan or a box fan aimed upward helps move the heat off the ceiling.

Don’t even consider vent free heat.

 

[tdkkart]

Don’t be afraid of venting out the roof. If done right it will never leak.

Except the inspector can see it when he drives by......

 

[pbon]

Use a vented hanging shop heater like mr heater, Reznor, etc., around 50k btu. So much better than a torpedo. Better for you as well if you are out there for a while.

 

[Woody325]

Thanks again to all!

My design since day 1 has been for the hanging vented unit, and that's what I ultimately would like to stay with if I can figure out the venting solution.

Venting out of the roof isn't a show-stopper, but is an aesthetic concern in addition to the anxiety of punching through my new roof (I can get over it). Inspector seeing it, or anything else, isn't an issue because I'm doing everything to code and wouldn't do it otherwise - just not worth the hassle (plus I live next to the Mayor).

The best possible solution for me is to horizontal vent, but again the problem is the 2.5' overhang. I believe my answer is to **** it up and vent out of the roof.

Thanks again for the sanity check

 

[yeldogt]

Do a sealed combustion cabinet heater .... they come with the vent. They are very easy to install as you only have to drill a 3" hole through the wall and attach the unit. What I always use. They are a little more money ... but when you factor in the included vent and the sealed combustion ... and time save. Worth it . You can even get them modulating .. and the heat is low where it should be.

 

[Showkey]

Just get a radiant tube heater.

Radiant tube with 9’6” ceiling would be very challenging as per install instructions and clearance needed:

https://www.lbwhite.com/application/files/6515/5715/0378/131112_REV.B.pdf

 

[toyotadriver]

Except the inspector can see it when he drives by......

Not sure how and why that would matter

 

[pbon]

If the overhang does not exist on all sides, could you put the heater on a side without the overhang? It would look funny and require support to go past your 2.5’ overhang and you unless it was straight you might exceed the max recommended length for horizontal.

Seems like you need to go through the roof. Done right, it works. Piping is cheaper also since you can use B vent rather than Type III stainless.

 

[Woody325]

Pulled the trigger on a Mr. Heater 50k btu unit and vertical vent kit from Northern tool - thanks to another thread on here I saw they have both on sale for $611 delivered.

Now i just need the foot of snow to melt before I can get on the roof

Thanks for the guidance and discussion to all.

 

[yeldogt]

FYI --- my studio is foamed and twice your garage size and I have a 38k heater in it.

My new house is 5000sf and the boiler is net around 60k ... all foam as well.

I'm glad you went with the smaller size

 

[toyotadriver]

For most garages, a little oversized on the heater is fine. For a house you are heating all the time...it’s better to not oversize it. A garage that is not heated full time usually will need extra BTUs to bring it up to temp and need more BTUs to keep it up to temp while you are working in it. Plus, when you open the garage door you have a huge heat loss to the outside so you need extra BTUs. A little oversized is usually a good thing when heating a garage.

 

[Woody325]

I was originally thinking ~35k btu would suffice, but the 50k unit was cheaper than any other option I could find. I was intrigued with radiant but apparently i don't have the ceiling height for it.