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Heating a lower level garage. Radiant or not?

copperkidcopperkid Member Posts: 22
I am adding an addition to our house which will have a walk out garage.  I will be using the garage as a shop mostly.  Being that the garage is not really exposed, except maybe 4-6 ft, how cold will the floor get.  I live in WI, and a buddy of mine says his garage is 40-50 during winter.  I plan on insulating the poured frost walls and the foundation walls with R-10, and the 2x4 walls with R-15.  Would insulating under the slab help with retaining the heat in the slab.  I almost think leaving the slab un-insulated would let the ground "heat" into the slab, providing the rest of the slab and walls are insulated.  I am using a mod con boiler for the living space above with a thin slab pex application, and possibly using staple up for the existing house. The floor will be insulated from below min R-30. I just want any thoughts and ideas on the best way to heat this space.  The thermal mass that I would have to keep heated might not be the best idea in my case. The time needed to bring it up to temp would be significant.  A gas modine heater is an option or a 80% horizontal flow would give me a A/C option in the future, but to stay on topic, since this is the radiant section.  How cold will a 42x 30 x 9 ft garage really get, I know you need a heat loss calculation, but how about a general idea, is radiant the way to go?  Cost isn't really a factor to some extent.  Ideas, opinions, advice??  Thanks in advance.  Awsome Site!!!


  • GordyGordy Member Posts: 7,122
    How many

    Windows and doors what size?

    How much wall will be fully exposed of?

    How much wall daylight?

    Where in Wisconsin.?
  • copperkidcopperkid Member Posts: 22
    more info

    Lannon WI,15mins  NE of Milwaukee , No windows, 2  9x7 doors, Doors will be very well insulated.  Only one wall will be exposed maybe 10 ft 1/4 exposure west side. 
  • GordyGordy Member Posts: 7,122
    edited March 2013

    So are the doors on the 30' wall or the 42' wall?

    Is one wall adjoining the basement of the home? If so which wall length?

    Or is this all garage space with home built on top?

    If you want radiant floors insulate the slab. Forget about the heat sink theory. You don't want to pay precious fuel dollars to heat the earth. Insulating the slab gives quicker response time, and easier to control.

    To answer your question on how cold it will get depends on a few factors. Such as how often garage doors will be opened, and closed, will there be any heat at all.

    I built a house with the garage under. Half of it. Daylight walls so half in the ground , and half out. I guarantee you that it won't stay 40- 50 in the dead of winter. It was 22x24 with 2x6 knee walls. Kitchen, and family from above with r 25 floor insulation. Not the best set up.

    I would stay away from the staple up. It will require higher supply temps than the rest of your floors, and you will be fighting the space temps below unless it will be conditioned all the time. If you do go that route plates are a must. Preferably do an over the top sandwich install.
  • copperkidcopperkid Member Posts: 22
    some more details

    The garage is being built under the living space, with the garage doors placed on the 30' wall. The 30' wall is adjoining the existing house.  I am planning on using the plates if I use the staple up.  I will be zoning the existing furnace for the kids bedrooms and front living room areas, to save on those pricey plates.  The new addition is being added to the rear of the house and will have the Maxxon floor poured with pex.  I just want to have some idea on the best way to accomplish heating this garage area.  What temp would the water/glycol have to be to keep it at 50 or 60 during the winter months.  I know it depends on insulation and heat loss calcs, I just don't have the time to sit down and figure it out.  Plus I got 3,000 ft of pex real reasonable, viega O-2 barrier.  So the extra cost on the insulation is not a factor.  Just trying to figure which way to go.  The engineer says 12" spacing on the garage floor is fine, I thought 6" on the outside walls is normal and 9-12" interior?  I will have drawings soon  to clarify this. 
  • GordyGordy Member Posts: 7,122

    probably around 30000 btus with 65 set point for the garage area.

    Pex spacing 12' okay for garage space your not going to be barefoot are you?

    Tighten up centers by the garage door area 8" or so, and maybe a couple tight centers along exterior walls.

    concrete floors with out pex is a missed opportunity. 12" spacing is around 1500' or so allowing for leaders, and tighter spacing in areas mentioned. 6 250' loops is it 1/2" pex you bought?
  • copperkidcopperkid Member Posts: 22
    Yeah pexless, if that's a word, concrete is a shame

    1/2" is what I got my hands on it's Viega brand.  My other choice is rehau for the living space area, atleast that's what my supplier is offering .45/ft.  Still looking for the best options, right now I'm putting in a NTI Trinity boiler with a TT Smart 50.  Whole house was calc'd at 70K  existing and new.  This is my last house, so I want the cadillac install.  I also have 3/8" copper tube, I was hoping to use maybe to heat existing floor.  They are full sticks so they're kinda hard to bend.  I saw that floor warming on the other post, and thought of maybe routering out my second layer of ply maybe?
  • GordyGordy Member Posts: 7,122
    edited March 2013
    3/8 copper tube

    Unless its soft copper you won't be able to bend the radius, it will kink on you. With soft copper it is difficult to get less than a 4" radius with 3/8 with out spooning the returns a little.

    If your dying to use the 3/8. You could use soft for the returns if you don't mind splicing a lot. Don't know how good you are at soldering, but more chance for leaks. I would stick with the pex save the 3/8 for another project.

    I routered the dinning room floor because 1/2" ply was already down. Messy unless you have a vac attachment it works. Tuff on bits, and need a 2 1/4 hp router to make any time at it.
  • copperkidcopperkid Member Posts: 22
    maybe i'll save the 3/8", here are the drawings

    Here are the plans.  Take a look, like I said the new addition is going to be 1 1/2 thin slab with pex.  The existing areas will be staple up unless there's a better idea.  The warmboard is too pricey, and the climate panels aren' t that much cheaper.  I figure staple up is the way to go with the extruded plates.  I decided to just put the pex in the garage and have it in there even if I don't hook it up right away.  Speaking of garage, I plan on insulating the frost walls with R-10.  Should I insulate the inside of the walls, the edges of the slab, or is the outside good enough.  Hope the drawings shed some light on my project.
  • GordyGordy Member Posts: 7,122

    Insulation detail just like shown in the section drawings.

    What are you heating the home with now?
  • copperkidcopperkid Member Posts: 22
    Using a Furnace

    The previous owner put in a brand new Heil 60K 95%, it's too small for the completed house.  So out it goes.  The insulation detail looks good for the lower garage, right?  Do I need to add anything?
  • GordyGordy Member Posts: 7,122
    edited March 2013
    Insulation detail

    Outside foundation wall, under slab, and perimeter of slab is the best detail like shown.

    What about air conditioning? Will you not use the airhandler for AC?
  • copperkidcopperkid Member Posts: 22
    Larger Furnace

    Since the house is going to be 2500 sq ft I need more cooling.  I'm putting in a 3.5 ton coil and a 3 ton condenser.  I am in the process of installing a Trinity TFT 100 boiler with a Smart 50 Indirect.  I plan on piping it primary secondary set up.  I like the downfired burner design, and the reviews on it.  Should have it all piped up by  next weekend. I was looking at the install manual and one diagram shows a primary loop with de-couplers for the take-offs.  The other one shows the primary pumping into the indirect and creating a primary loop with the indirect tee'd into the primary loop.  Don't understand why they show two different diagrams??  See if I can get a print.
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