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Underslab radiant heat-new garage construction

 
Old 10-25-2015, 09:31 PM
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dplotkin
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Default Underslab radiant heat-new garage construction

Many of you were helpful when I posted my new 40 x 40 garage on a home I'm building and asked for suggestions.


I need to quickly decide on 2 gas unit heaters (1,600 sf space with 12'.6 ceilings) for around $8,000 or under slab radiant heat using a hot water loop off a small stand-alone boiler. The house is forced air. The price I have to do that is $23,840 including an extra inch of concrete (5" total @ 4000 psi).


I'm not going to be taking cars apart in this garage and see this expense as overkill, but you can only do it once, and I hear its really optimum for heating a garage. What do you fellas think?


Dan
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Old 10-25-2015, 09:46 PM
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Originally Posted by dplotkin View Post
Many of you were helpful when I posted my new 40 x 40 garage on a home I'm building and asked for suggestions.


I need to quickly decide on 2 gas unit heaters (1,600 sf space with 12'.6 ceilings) for around $8,000 or under slab radiant heat using a hot water loop off a small stand-alone boiler. The house is forced air. The price I have to do that is $23,840 including an extra inch of concrete (5" total @ 4000 psi).


I'm not going to be taking cars apart in this garage and see this expense as overkill, but you can only do it once, and I hear its really optimum for heating a garage. What do you fellas think?


Dan
Your profile doesn't say where you're located, so I don't know what kind of weather you have. What's just as important as the type of heat source you have is how well insulated and moisture-barriered the slab is, so the floor is always warm and dry instead of cold and clammy whether the heat is on or not.

We laid down a 10-mil poly Visqueen moisture barrier on the ABC, then laid 2600 sq. ft. of 4' x 8' sheets of tongue-and-groove 5/8"-thick high-density closed-cell foam with heavy foil on both sides, then rebar over that, and poured the slab. 90 days later steel shot-blasted the slab and poured 2 coats (24 hours apart) of solvent-based industrial epoxy resin. Always warm and dry, ZERO moisture migration.
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Old 10-25-2015, 09:58 PM
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Originally Posted by JohnZ View Post
Your profile doesn't say where you're located, so I don't know what kind of weather you have. What's just as important as the type of heat source you have is how well insulated and moisture-barriered the slab is, so the floor is always warm and dry instead of cold and clammy whether the heat is on or not.

We laid down a 10-mil poly Visqueen moisture barrier on the ABC, then laid 2600 sq. ft. of 4' x 8' sheets of tongue-and-groove 5/8"-thick high-density closed-cell foam with heavy foil on both sides, then rebar over that, and poured the slab. 90 days later steel shot-blasted the slab and poured 2 coats (24 hours apart) of solvent-based industrial epoxy resin. Always warm and dry, ZERO moisture migration.

I'm in Western Massachusetts, winters are cold and damp. The radiant heat is specified with insulation from a system manufacturer/provider. Sounds to me as if you believe under slab insulation is more important than heat source. In that case maybe I'm better off doing the insulating you did but use unit heaters.


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Old 10-25-2015, 10:04 PM
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Originally Posted by dplotkin View Post
Many of you were helpful when I posted my new 40 x 40 garage on a home I'm building and asked for suggestions.


I need to quickly decide on 2 gas unit heaters (1,600 sf space with 12'.6 ceilings) for around $8,000 or under slab radiant heat using a hot water loop off a small stand-alone boiler. The house is forced air. The price I have to do that is $23,840 including an extra inch of concrete (5" total @ 4000 psi).


I'm not going to be taking cars apart in this garage and see this expense as overkill, but you can only do it once, and I hear its really optimum for heating a garage. What do you fellas think?


Dan
Well, first off $8000 for two gas unit heaters, for 1600sf?
I live in Wi,cold winters, My garage is 1200sf, 12' ceilings, 16' high cathedral by lift, and I have a 75,000 btu Modine hot dawg, about $850, and it is plenty of heat. I work for a plumbing contractor, and we install in floor heat. In floor heat is the cats azz, but for simplicity I went the route i did.
Sounds like you don't "live" in the garage like I, and others do, so I would go the most economical route for heat.
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Old 10-25-2015, 10:25 PM
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Default In Floor Heat in Ontario Canada

I live in a cold area . About 7 years ago I built a 1200 sq ft addition to my shop and installed an in floor system myself . I insulated under it with a specially designed mat that is about 1 inch thick and consists of several layers of foam with outer layers of plastic . It came in 50 ft rolls about 10 ft wide and installed easily . I heat the water with a Taggaki demand water heater .
It definitely is nice even heat but the install cost is many times the cost of a unit heater .
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Old 10-25-2015, 10:49 PM
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Ken Sungela
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Radiant heat is great as I installed it in the first floor of my house and made provisions in the manifold to hook up a garage circuit for a nominal cost. It may be worth it for you if you plan on working on cars in the garage often, but I think a ceiling hung heater may be more practical, unless money is no object. Something like this Modine HD75AS0111 may work well.
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Old 10-26-2015, 12:13 AM
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I don't know about everyone else...but unless you heat the slab all winter I would be miserable while it s catching up on a cold day.

I had a friend that had cabin in Colorado with radiant heat...coldest most worthless sob I ever spent time in, and he spent a fortune on it.

Good insulation on the building and thermostatically controlled heat and a/c is best for me. I have propane (..rural area) which will heat my shop in a hurry (brings it up to 70 degrees in 25 minutes on sub 30's days) and will burn you out if you like it hot. I could speed dry paint if I wanted too.

Oh yeah...I only used 80 gallons of propane in the last year, with 4 inches of closed cell foam insulation on a metal building. You could practically heat that building with a candle. It is a two room 40 x50 shop building that I heat whatever room I am using that day (one 20x40 dirty room, welding, water sanding, paint, whatever,) and one 30x40 clean room (engine work, auto lift, gun finishing, reloading etc). I'm in the shop more than in my home ...

Insulation is the key...closed cell foam is impossible to beat imho. It also makes the building air tight. It is expensive ...but that's where the $$$ really make a difference.

I bought residential heat and cool units, one for each room(used reasonably high efficiency later models). Both are propane heat, R22 a/c. A friend and I installed them ..less than a $1100 spent on both units combined, which is way cheap unless you are a good scrounger too. ( I have rental property and know a few helpful people.)

I could build another shop for what some radiant heat systems cost....or buy another car, or......

Happy trails...Stan

Last edited by Stan's Customs; 10-26-2015 at 12:19 AM.
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Old 10-26-2015, 06:04 AM
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I'm with Stans on this. Foam insulation and Propane heat, toasty in winter and actually stays pretty cool in the summer. Low initial cost and little or no maintenance

.....




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Old 10-26-2015, 01:50 PM
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Originally Posted by skids View Post
Well, first off $8000 for two gas unit heaters, for 1600sf?
I live in Wi,cold winters, My garage is 1200sf, 12' ceilings, 16' high cathedral by lift, and I have a 75,000 btu Modine hot dawg, about $850, and it is plenty of heat. I work for a plumbing contractor, and we install in floor heat. In floor heat is the cats azz, but for simplicity I went the route i did.
Sounds like you don't "live" in the garage like I, and others do, so I would go the most economical route for heat.
I live in Calgary Alberta, and when my house was built 17 years ago, they installed an in-slab hydronic heating system that covers the entire lower level [2000 sq.ft]. There are 5 circuits, 2 thermostats (one for the garage with 2 circuits, which is neat because if I'm working on a car, I can just heat the floor under it, and not the whole garage, by closing the valve to the circuit not required. Powered by a 93,000 BTU/hr natural gas fired Burnham "Boiler" (although it doesn't really boil). Upstairs is heated with a natural gas fired forced air furnace, with a few ducts for downstairs, which I keep closed. I think I got a deal on this set-up, as the home builder was a friend in the Corvette club .








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Old 10-26-2015, 07:57 PM
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Default Underslab radiant heat

I have a five zone system in a 1,500 sq ft shop with in floor heat. It is wonderful and very comfortable. But I would never do it again. The shop is only used for car storage and occasional work. I have to keep it at reasonable temperature, 55-60, to be comfortable working. But I may go two or three weeks and never enter the shop. I have to maintain that heat level as it takes many hours, sometimes days, to raise the temperature just a few degrees. It is very costly to maintain the heat at a comfortable level when it is not being used on a daily basis. With a forced air system you can easily maintain a 45 degree temperature and raise it to a comfortable 55-60 degrees in an hour or less. So if you work in it everyday then the in floor radiant is the way to go. For part time stuff I would go with the forced air.
I'm located in central Illinois and it does get very cold.
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Old 10-26-2015, 08:22 PM
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My 2600 SF attached garage is super-insulated; besides the insulation and moisture barriers under the slab described earlier in this thread, the walls were framed with 2x6 instead of 2x4 to accommodate R-26 insulation, the ceiling has R-58 insulation, and the two custom-made 18' x 8' sectional doors are 1-1/4" thick steel/foam/steel, with tubular seals between sections.

My 16' x 16' retirement office is in the garage, and I'm out there all the time, every day. I have a Reznor 125,000-BTU natural gas power-vented electronic-ignition unit heater that hardly runs at all after the morning warm-up (could have gone with a 75,000 or 90,000 unit - the "super-insulation" package turned out to be much more effective than we thought). The garage has never been below 55*F.

For cooling I have a Mitsubishi "Mr. Slim" 42,000-BTU mini-split system; it cools 2600 SF on 90*F days with no problem at all.

These systems work effectively due to INSULATION, well thought out and designed-in when we built the house. If you cheap out on insulation, you'll pay the piper big-time for gas and electricity.
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Old 10-26-2015, 08:47 PM
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Thanks John and the rest of you.


John, why didn't you use closed cell foam? My house is all 2 X 6 as well and I was thinking of spending the money I would have otherwise spent on radiant heat on closed cell foam and then use 1 Modine Hot Dog HD100 gas fired unit (80,000 BTU input).

I will be using the garage principally for storage of my cars and during the winter I'll be doing light maintenance and detailing from time to time. I will be in the garage far more often during the driving season when heat isn't needed.

So as good as radiant heat is, I'm thinking its overkill in my case, better to spend on insulation & doors, yes?


Dan
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Old 10-26-2015, 09:03 PM
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Originally Posted by dplotkin View Post
John, why didn't you use closed cell foam? So as good as radiant heat is, I'm thinking its overkill in my case, better to spend on insulation & doors, yes?


Dan
We did closed-cell foam (with heavy foil on both sides) under the slab, and used a more conventional product for R-26 in the walls. I'd definitely spend the money on insulation and doors rather than on radiant heat.
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Old 10-27-2015, 11:36 AM
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Originally Posted by JohnZ View Post
These systems work effectively due to INSULATION, well thought out and designed-in when we built the house. If you cheap out on insulation, you'll pay the piper big-time for gas and electricity.
That's so true. My house is 2 x 6 construction, garage is below the master bedroom. It had the typical insulation in the walls and leaky aluminum windows.
I redid everything in 2005 myself. Ordered double pane vinyl windows that were 1 1/2 inch deeper, wrapped the entire house in Tyvek, 1 inch R-Tec foam with vapor barrier over that and cement board siding.
Kept track of the propane usage for 3 years - the result was a 60% reduction in my heating bills.
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Old 11-01-2015, 08:48 AM
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Let me add my two cents worth. I have had in floor heat in my last three homes, including the garages. There is nothing like it for comfort. I keep the garages heated to around 50-55 all winter (Lansing Mich. area) and it's really inexpensive. The beauty of the system is that when you're on the floor, it's warm and comfy even though at the ceiling it may be cooler. Forced heat systems work backwards; heat rises and to get it warm near the floor, you are ending up with a lot of heat up near the ceiling where it does you no good.
The key is the under slab vapor barrier and insulation, including where the side of the slab butts against the footing. You don't want any transfer of heat from the slab to the footings.
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Old 11-02-2015, 09:21 AM
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I agree radiant floor heating is the most comfortable, although slow warming up. I live in NC where winters are moderate and a forced air heat pump system works well for me. Forced air allows you to address heat and humidity in the summer. I have 10 ft ceilings but ceiling fans on reverse push the warm air down in the winter.
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Old 01-18-2019, 04:59 PM
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In Chicago area. 3 car attached garage. I have a 66k btu between the stud gas furnace w 2 speed blower. Takes garage to 65 deg in about 30 min.
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Old 01-18-2019, 05:06 PM
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3+ year old thread.
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Old 01-18-2019, 05:08 PM
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It there's anyway to get power out there, think about a Mr. Cool mini-split. It has heat and cool for winter and summer. I installed one this fall (DYI) and love it. It was a 120V model.
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