Garage Workshop Super Insulated Radiant Floor

How I made my Garages Super Insulated Concrete Floor. This building is going to be heated because it is both a garage and a shop. I set up radiant tubes in the floor for the hot water to circulate. This is a hydronic radiant floor. I insulated between the ground and the concrete slab because the slab is always going to be hotter than the ground.

There is lots of rebar, probably over doing it a bit. The slab was 5,000 psi concrete and 5 inches thick. This slab is way overkill, but I didn't want to worry about it. Now I could add a lift in the future if I want to.

The foam board used is high-density "Geo Foam" which came out of a factory in RI. The foam was great and I would use it again. I secured it to the walls using Loctite power grab adhesive. There is a link below. The floor insulation is a total of 14 inches (R-56) and the wall is 2 inches (R-8). The wall was later framed out for another R-20 of cellulose.

Read more details about this project here:

My dad and neighbor, John, are seen because they both helped out so much with this. Thank you.

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  1. Love the new intro! 🙂

  2. Nice job David!  I like the banjo music!  What a great experience implementing so many interesting design aspects.

  3. Now that’s how you build a building ! I just made the same comment on your truss install. So, the floor is R-56 ? Awesome ! What is the R-VALUE of the ceiling ? I see in the very beginning of your build that it looks really deep, I’m dying to know and also how is the building performing heat wise ? Thank you.

  4. Thanks. The ceiling and walls will get their own video. I’ve got the raw footage, but I need to compile it. But, spoiler alert, the ceiling is an R-100. No particular reason for that R-value other than it seemed like a nice round number. Performance is amazing. The first winter I heated it with an electric water heater, 3,000 watt elements. That is about 10K BTU’s per hour. I don’t need all that, but it was just what came with the water heater. I’ve got more videos on my channel about converting it to solar heat.

  5. Hi David,        Was wondering if there is any benefit/downside to adding a layer of epoxy to the cement floor? Since you said the garage floor is level you could probably add the epoxy in layers to give it the grade you want. Would the epoxy inhibit the radiant heating system?   Cheers,          Bill

  6. Hi Bill, I don’t think the epoxy would inhibit the radiant floor. I did paint the floor for ease of clean-up, but not to adjust the grade. Thanks for watching.

  7. I like how you put 14 in of foam under your foundation floor and did the radiant floor heating over that. The one regret I have the building my shop is not doing the radiant floor heating in it.

  8. DavidPoz you do realize after about r50 your just wasting money right? Your gaining very very little for every r value.

  9. Ryan, who cares ? DavidPoz has one hell of an insulated building ! And even if he gains only a small amount after R-50, he’s still gaining and I say bravo !! I’m an insulation installer, so I may be biased !

  10. Hi Ryan, Thanks for watching the video and joining the discussion. Probably most of us watching an insulating video are aware of the “law of diminishing returns” with R-value, but just because the last inch of insulation does less for me than the first inch is no reason not to install it. Most heated garages (commercial and residential) that I’ve worked in need massive boilers. I’m going to be heating my garage this winter with just some solar panels. I would not have been able to achieve these results with just the first one inch of insulation (as the reference to the law of diminishing returns would suggest). But it is a great discussion, so thank you for bringing your opinion to the table.

  11. You should run your pex under your rebar! That way in the future if you wanted to drill the floor for an anchor you would hit the rebar before going thru your pex tubing.

  12. lot of great tips there!  Thanks for sharing!

  13. You welcome, thanks for the compliment.

  14. Holleran Properties

    Rebar was the smartest thing you did. It will hold that concrete together tight. Wire mesh gets stepped on during the pour, and is hit and miss as to its height. Don’t worry, your young and you got a few more shops in ya. Good luck, “W.W.”

  15. You are putting the wall insulation on the wrong side of all that concrete thermal mass. Passive Haus, basics.

  16. There are many ways to make an efficient envelope, but only a Sith deals in absolutes.

  17. Rebar in the centre of a concrete slab does almost nothing. It has to be either at the top of the slab or at the bottom, depending on whether you are trying to resist downward bending or upward bending of the slab. Speak to a civil engineer.
    Very nice thermal insulation though.

  18. Total overkill david. All you need in the floor is 1/4 ” roll out reflective insulation. Focus the insulation on walls and attic. You are correct, 6-6 paving wire works so much better than rebar for routing the heat pipe.

  19. Foil “insulation” is one of the most miss-understood products out there. The purpose of adding the foil is to reflect radiant heat. Heat transfers by radiant, conductive, and convection. It is important to remember that radiant barriers only work if they are clean, and there is an air-space between the surfaces. Given that I am pouring concrete directly onto the insulation there is no air space. There is also no convection currents between the two materials. So the only heat transfer we are concerned with is CONDUCTION. (basically foil does nothing under a slab). You mentioned 1/4″ . This would provide at most an R-1 (but probably lower with most products out there). Given the best case scenario of an R-1 in your suggestion, we can do a simple heat loss calculation to compare it with the R-56 I installed. I’ll assume a constant ground temperature of 50*, slab temp of 80* and a five month long heating season (pretty conservative). Do out the math and your method will lose 129.6 Mbtu’s to the ground, costing you $9,116/yr. with my electricity cost. My method loses 2.3 Mbtu’s to the ground, costing me $162/yr. Remember, this is only the cost of the energy being lost to the ground, it does not take into account loss through walls and roof.

  20. If you put sand under your ins. and concrete that is your air space. Also if ur slab temp is 80. ur probably working in ur undies. Most people I know keep it at around 55-65 degrees. You don’t have to believe me, that’s your option. 25 yrs the senior. Never saw 9,116 anywhere. just my 2 cents.

  21. Hi Paul, If I did this again I would install the PEX before the Rebar. Two possible ways: by stapling the pex to the foam, or laying down 6×6 W.W. mesh and zip tying pex to that. Then the Rebar grid could be laid on top of the pex and could be easily off-set. Very cool about your project. Are you planning on a wet jacket on the wood-stove to heat the water for the radiant floor?

  22. Thinking more along the lines of a stainless steel coil in the firebox. I know it’ll take some experimenting and maybe I’ll even end up with solar like you’re doing. Do you have it up and running yet? Did you make your own “solar panels”?

  23. I’ve heard good things about a SS coil in the firebox. I hope you make a video on that when you get there, I would enjoy watching it. I salvaged old solar panels, here is a video on how I did it:

  24. I have used self leveling concrete before. Yours was not wet enough.

  25. Thanks for sharing!

  26. Quality job right there nice to see someone knew there limits and got a pro to finish the floor.

  27. I layed out a couple of tape measures for reference. I then videotaped the PEX (which is ziptied to 6 x 6 wire mesh) before pouring floor.

  28. Nice job but way overkill for a garage. If your building site is dry, you do not need to use the foam board. Instead, use a plate compactor to create a compacted base, use, as you discuss, welded wire, hold it up with chairs, zip tie your Pex and call for the concrete truck.

  29. I like pushing the envelope when it comes to energy efficiency. I’m heating this garage with only solar energy, so the load must be as low as possible. Thanks for watching.

  30. Thanks for your response. If you are using solar hot water, you do need “suspenders and a belt”. I live in Alaska and in SW Idaho. I built a shop in Alaska with in floor heat and it works great. I am going to build a shop in Idaho soon and may use solar hot water for my in floor. How did yours work out ? What part of the country are you in ?

  31. Lots of good notes. You learn as you do more and more. Ask proffessionals if you arr midsing something. They might have recomended the slope.

    As for the self level. Ground was probably to dry and sucked the moisture out of it. Increasing dry time.
    Probably could have done larger gravel, then screed gravel then foam. Local build code would probably tell you

  32. Maybe its self levelling in small edged sections- not wide spaces. What hard work that caused you 🙁

  33. I live in central Massachusetts. As for how it is working out, the garage is awesome, but the solar part I’m still tweaking. Even last night I was finishing the plumbing on a new heat exchanger. After our next sun-day I will be able to tell if that grabs enough BTU’s. I’m posting the videos on this channel so if you subscribe you can follow along. Do you have any other questions? I’m putting together a list and plan on answering several in a video.

  34. Next time I will do as you said, level gravel, then foam. I won’t be wasting my time with the “self-level” stuff again.

  35. Way tooo dry for a self leveling product flow fill product. They did not do you right at all – and cost you a lot of extra work, time, money, and headache (obviously) Nice build though. Overengineering is never a bad thing – leaves you a lot more options for the future instead of having “just enough”

  36. Hello from DownUnder, Fantastic looking shed!
    Notice your table saw work bench, look great. Any chance of a few photos of the work bench.
    Good luck with the build.
    Merry Christmas.

  37. Hi David, thanks for watching. The workbench was designed by Ron Paulk. I purchased his plans from his website. He also has a series of videos on how to make it. Just google “Paulk Workbench”. I’m happy to make a video of mine and will add it to my list. I appreciate the feedback, it helps me tune the channel.

  38. Thank you David. I will google “Paulk Workbench”.

  39. Vapour barrier before foam then use you’re router to put channels for pex then steel and if you want to get real anal rout where the steel sits so as someone else said ” you hit steel before pipe , but if money’s no object heating supplies have foam 2″” thick with channels in it .

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