Help me with my unit heater placement

[jvitez]

OK gents, I'm at the planning stage for heat. After much consideration due to various issues, I've decided on forced air unit heaters. I have NG and a 400 amp main service so both heat sources are equally available. NG is about 45% the cost of electric right now, but I won't be heating the garage all winter, just when I'm working (playing....) or thawing out vehicles. Insulation is R22 Roxul in the wall, ceiling will be R40 blown in cellulose. The exterior is acrylic stucco with Tyvek overtop OSB sheathing.

I can do all my own electrical, but we're not allowed to touch NG here; it must be a licensed gas fitter, so NG installation costs are far higher.

Now, my main issue is the L-shape of the garage. It's 1800 sq ft outside dimension, about 1750 using inside measurements. I've had the HVAC contractor who installed the geothermal heat when our house was built in 2006 give me some ideas, and the two he came up with are the two drawings.

Option 1: one NG unit heater blowing across the longest dimension. I can use just that and see what happens, but I predict the far corners will be cold, so I could install 5 kW electric unit heaters in those positions if needed.

Option 2: two NG unit heaters back to back like in a warehouse. The plan would be to have air circulation as I've drawn. No need for electric supplemental heat with this option.

Option 2 is clearly the better choice, but at a much higher initial cost.

My questions:

1. What's the likelihood of Option 1 doing a good job, with or without supplemental electric heat?

2. Any other placement ideas possible? Venting must be toward the 40' rear wall with the single door (tractor door).

Thanks in advance!

 

[regguy1]

I'd say 2 looks more efficient

 

[54stude]

Any thought to putting some type of roll up or sliding door in that opening and having one side "warmer" than the other one?

 

[p_mori7]

How about #1, but angle the unit a wee bit towards the man-door. Perhaps then you could add an extra vertical diverter on the front of the unit so it blows into both areas ?

 

[Charles (in GA)]

Vertical louvers if possible, spread the air around as pp mori7 suggested.

Don't forget the ceiling fans. They will do a fantastic job of spreading the heat around.

Charles

 

[metalTobman]

Option one: you're going to be cold!
Option two will work, but there will be cool areas. Good place for
Probably just fine for a workshop. I would add that supplemental electric heat you mention to the area you plan to use for detail or assembly work, just for comfort.

 

[jvitez]

I did consider installing those see through plastic vertical curtains used in cold rooms between the two halves of the garage, but my plan is to use the top part for work/play and the bottom part as daily driver parking. Good point about a ceiling fan. I was going to install the heaters then see what I'll need for air circulation.

metalTobman: LOL! Thanks! My bench will go on the right hand side wall by the NG heater in option one. I was planning on some local heat right by the bench one I see how the main heater(s) work out.

Really, a ducted furnace would be best, but I'm trying to not blow the budget, and I don't want big ducts running across the ceiling interfering with my lighting plan. Decisions, decisions.....

 

[metalTobman]

You're right, a furnace and ductwork would be a good way to get more even air distribution. If you did that, it would be best to have it sized by a pro, so you can get the needed air volume to each duct. Dampers are a necessity, you need them to balance the system.
I'll just climb up on my soapbox here, and say that your garage is well suited to radiant tube heating. I would put one in each of your two areas, and that would result in two zones. Another plus is easy venting through the wall.

If you are intending on venting your unit heaters or a furnace through the wall, check local gas code and read the heater manufacturer's instructions.
It is not always possible to vent horizontally, in some cases the distance will be too great, in others, a power venter may be required. It depends on the appliances you choose to heat your garage, they are not all created equal.

 

[jvitez]

Yes, radiant tube heaters would be ideal, but everything must be vented out the back wall due to all the garage doors in the front, plus appearance, ie wife approval factor, so no venting out the side wall. One radiant manufacturer I contacted gave me their venting limit, and it would be exceeded if I tried to vent it out the back wall if I installed one in the bottom half of the garage. This is one reason I decided on forced air heaters.

A ducted furnace would be best. But another problem is that I only want to heat intermittantly. Our province passed a reg requiring high efficiency furnaces only be allowed to be sold here, and condensing furnaces freeze their vent pipes if left in an unheated environment.