If you build a new garage...Heating and Insulating.

[work sucks]

I am looking into building a 30 x 40 or so garage. (stick framed) What is the best method to heat that space. Would you do a styrofoam insulated and poured frost footing? Poly under the main slab? Rebar or mesh? I plan on sheet rocking it and using fiberglass bats and maybe blowing the ceiling.

Thanks for the input...

[cavalierowner]

If it were me, I would use gas-fired unit heaters. Relatively cheap and easy to install, assuming you have a gas source.

If this is a detached garage, it's hard to beat the economy of a floating slab. And if you're heating it, there is no question there should be insulation either under the slab if a floating slab or around the perimeter to frost depth if a conventional foundation. In fact, the building inspector will probably require insulation if he knows you're heating it. Be sure the board insulation is not the white beadboard or isocyanurate; that stuff sucks up water like a sponge and becomes almost useless.

You might want to consider putting 1/2" or 5/8" plywood on one or more walls. It makes it really easy to mount shelves, attach hangers etc. Check with the inspector to be sure there are no issues with fire ratings, because plywood won't give you that. Fire retardant plywood may be an option if you have a problem, but has to be approved by the inspector.

[Loose]

radiant floor heating

[goose89]

I don't know any of the answers, but I'm jealous. If you want a regular boat storage customer over the winter...

good luck with my dream....

[BoxMN]

When I do my 1200 sq ft detatched at the cabin (God knows when...) I will put foam under Wirsbo in-floor heat, 2x6 walls, 2" high-quality steel insulated doors, and use off-peak electric boiler (with antifreeze, not water). That is what I have in my cabin floor and it is awesome and quiet efficient - I did not add it to my attached garage floor and wish I would have. I'll zone it for three areas, but probably only use two zones, one a shop or better yet "fun time bar area"

Plan is to put storage trusses up there for "bonus room" type area, and blown in where I can, and use batts or spray the rest, depending upon how rich I am then, hahaha! If that is the case, I will prolly use newspaper

Good luck, nice big garage!

[CaptainBly]

Is the garage going the be wide open or are you going to separate it with a wall. I have one about that size, part is heated and the other is just cold storage. You can fire rated paint for plywood to, I don't know the specs on that though.

[Tom7227]

I agree with BoxMN that the heated floor is nice but the drawback is the time it takes to run the heat up. If you're going to use it regularly for more than parking then I'd go with the heated floor. But if it's only occasional use on the weekends then I'd probably go for a hanging natural gas unit - maybe two with the size you're talking about and have them blowing diagonally from the front two corners.

[Skeeter21i]

You should be able to float a 30x40 slab. As a precaution you could pour the edges thicker. I went 30x54 for my garage and poured the edges at 16"x16". I wanted to go a bit bigger but the county required footings and frost wall for anything beyond what I built. I went with two course of concrete block with an eight foot framed wall. With the wet environment in a heated garage you need to make sure your vapor barrier is done properly. If the budget allows it you can upgrade to spray foam insulation which will help eliminate any future moisture issues. I have radiant heat with an off-peak electric boiler and am happy with it.

[BoxMN]

The best of both worls would be in floor heat, leave it at about 40-42 degrees, and a gas vented furnace that you dial up when you want to watch football, work on boat or project, or whatever. That would be pretty efficient for just about any use, but higher initial cost. Also, if you don't have off-peak availability in your area, I wouldn't use an electric boiler, it will spin the meter pretty good after you open those big doors!

FWIW - in my 1000' garage here at home I just have our old house furnace (30 yo gas) and r15 in walls and ceiling and I leave it on all winter, at about 38 degrees, and just flip it higher when working out there. It really doesn't use as much extra gas as I thought it would, and I could insulate much better than I have it. And my old furnace is not high efficiency at all... 75k btu I think. The key is keeping garage as low temp as possible without going below freezing, then just kicking it on when you need it - it takes about 10 minutes to get warm... about half hour to get downright toasty even when really cold. So don't need in floor, but with off-peak it will cost nothing to keep it above freezing all winter long.

[work sucks]

Thanks for the input guys!

This garage is going to cost a small fortune, but will be worth it. I have to move to build it. I don't have the room where I live, but the house is on the market now and I am looking for a place with a couple of acres so I have room to build it. Yes I will have a gas source even if I need to put in and additional propane tank to do it.

I'm sure I will have more questions, but I will have to wait until I move to get started....

[cavalierowner]

Using a conventional forced air furnace is probably the best solution as long as you intend to heat the garage all the time and don't foresee ever letting it get really cold. The problem with starting a furnace if you get it really cold in the garage is that it will tend to short cycle. Heres what happens: the furnace starts as usual with the burner warming up the heat exchanger. At a certain temp in the heat exchanger, the fan comes on. But the air coming back to the furnace thru the return air is so cold it cools down the heat exchanger in a matter of a few minutes and the fan stops. Then the burner has to heat up the heat exchanger again and the cycle repeats. I have actually seen houses being built in the winter where the HVAC contractor had to bring temporary heat into the house to warm it up enough that the furnace could be started; it was actually so cold in the house that the furnace could not get the temperature up. That's why I originally suggested a unit heater, not knowing if sometime in the future you may not want to heat the garage 24/7.

[PurpleFloyd]

I guess if I were going to build a heated garage the first thing I would do is to use SIPS panels for the sidewalls and then either a high efficiency boiler like a Munchkin, Weil McClain etc or if the building is small enough, a Tagaki TK Jr unit.

[work sucks]

Sips...Funny you say that, my Dad owns Panelworks Plus. I am also going to look into a deal on those things for sure!

[tonkapat]

I would run wirsbo in the slab no matter what. Even if you plan on going with space heaters you will always have the option. Who knows what will happen to energy prices 10 years down the road. Waste oil boiler or external wood boiler are options also. Sounds like an awesome garage to me.

[PurpleFloyd]

Sips...Funny you say that, my Dad owns Panelworks Plus. I am also going to look into a deal on those things for sure!

Well heck, if your dad own that company it should be a done deal. Then when you are done ask him if he needs any more sons because I could use one too. JK.

Are they staying busy right now? When I did the design for our new Fire Hall we are currently building in town I pushed for and got it built using SIPS panels.

[work sucks]

He is staying fairly busy. He sells them and does the planning and contracting of the installation of them. He uses the panels from Extreme Panel out of Cottonwood,MN. Neat product though! I can even do a SIP foundation in addition to the side walls. Who did you use to do your project?

[Tom7227]

I have to move to build it.

Before you make an offer on the new place check with the local officials and see if there are any restrictions on what you can put up. Many places have square foot limits, some have limits on building type .... Could be a real whizzer if you bought and found out you could only have a fairly standard 24 x 24. I suspect that the closer you are to the twin cities the tighter the restrictions would be.

[reddog]

Shallow, Frost protected foundation is the only way to go, whether it is a monolithic slab, or a footings/block and internal slab.

Here are the photos from my cabin/garage in South Dakota. (2001) 18X30 2 story cabin with a 24X28 garage, all insulated slab on grade.

The only thing I wish we wouldve done, was to add the Wirsbo tubes in the slab, even if we never hooked up the boiler and pump. I was on a tight budget at the time, and didnt really think about it, but I know I wouldve had the boiler up and running by now.

Oopps, cant post links here, so I will post one picture, then you can right click on it for the properties and follow the address from there and follow the properties to my online album.

SIPS would be an awesome option!

[titelines]

I would 2nd the SIP panels. My wife designed our place and the cabin and detached garage are both SIP. Cannot believe how "tight" and efficient they are. We've got 8" on the walls and 10" on the roofs. They cost a bit more up-front, but you make up for it with the reduced labor costs, they go up in no time.

Our garage is 26' x 27' and is heated with a 45,000 btu Hot Dawg, with a tank outside. Good insulated doors and spray foam around the windows. Very good system for the weekend warrior.

Floating slab, with insulation around the sides down to the frost line. The interior walls are also very conducive to hanging shelves etc.

Hope this helps.

[hawkeye43]

We have a 48'x68' shed that has 8" foam sheets in the walls and 18" in tha ceiling. we keep it at 48 deg.,that is plenty warm to work in there with just a t-shirt on. There is one third of the floor that has in-floor heat. The outdoor wood boiler was converted over to waste oil that heats the water. It burned about 1400 gal. of waste oil this winter. This system also heats the 1800 sq ft house and another 40'x90' shop. Its a good way to heat, but last night the boiler shut down because someone forgot to check the oil in the storage barrel and it ran out of fuel.

[BoxMN]

Floating slab, with insulation around the sides down to the frost line.

Hey titelines, how did you do that? dig around after, or put the foam in before the pour? Also, how did you attach finish material after, and what did you use? I am curious as that sounds cool, but I am not sure what you did... Thanks, I am weekend warrior type, so not totally knowledgable, but I did build my own garage, so know a bit. I didn't insulate floor or foundation (poured slab) here at home when I did mine, as I didn't think of insulating until after. I am going to correct that for the cabin toy box some day Thanks for info!

[reddog]

BOX,

Look thru these 19 pics

http://imageevent.com/okoboji_images/frostprotectedfoundation

They should take you thru start to finish,(the way I did mine, and Ive done hundreds of Shallow Frost Protected Foundations)

Both these slabs (attached garage and cabin) were completed in 3 1/2 days, start to finish, including the dirtwork to excavate and backfill by three guys. Myself, a dock builder and a retired lineman.

The garage (unheated)doesnt have edge foam, but the foam extends past the perimeter of the garage 48" in all directions. The cabin has slab edge foam attached. (look at pic # 9 for the detail of how to attach in a monolithic pour)

I applied a cemetitious coating over top of the foam for protection, and held the wall sheathing down 1" and started the siding 1/2" below that.

[BoxMN]

Thanks reddog, that answers several questions.

Curious as to why you may not have put in Wirsbo? Possibly you answered it in other post, sorry if so.

I think in my cabin they (contractor built cabin, I was not able to be there much during construction) used a foil type insulation under wirsbo tube on top of soil rather than 2" foam. I don't recall asking why now, not sure why I didn't... I do know they used 2" foam on top off all water/septic lines and under grade to keep frost away from them, and said it was virtually impossible to ever drive frost through, and even going around it would take a lot... but I forgot to ask why not 2" under slab... hmmm... I was slacking

Great picks, thanks!!!

[reddog]

I built our cabin in 2000, and wirsbo was relatively new , at least to me, but I sure wish I wouldve at least put the tubes in.

2 Inch 2 lb density foam under unheated structures. (2lb density allows the load bearing capacity for the structure)

1 inch under heated structures as a thermal break from the earth temp.

because of the size of my cabin, I opted for 2 inch throughout, ainly because of the logistics of building out in the sticks. for the 18x30 cabin, it wasnt that much more money.

[Tom7227]

RD -

Curious about why you put the foam outside the structure and why it was horizontal rather than a vertical break along the perimeter of the building. I'm not in the trades and I am just curious to know what the thinking is.

Thanks

Tom