Questionable Installation of Radiant Floor Heating System
I’m having a detached garage/workshop built in Ontario, Canada (Zone 6; in USDA terms Zone 5, as far as I can tell) and will be using radiant floor heating. I’d like some feedback on the work that the contractor is doing, as it’s not being done exactly as I’ve seen described on the forums/articles here and in videos and need to know if I’m nitpicking or whether it’s substantial:
1. They’re not running the foam board insulation along the sides right up to where the level where the slab will be so that it will have a “clean look after the concrete is poured”, see attached photos (the red line is where the top of the slab will be). I expressed my concern that the slab will leak heat into the foundation walls if it’s left like this and was told that the PEX will be 9″ away from the wall so it “won’t cost you 10 cents all year”.
2. I asked what R value the foam is as I’m concerned that it’s insufficient and they couldn’t tell me. The foam board itself doesn’t say, but it’s Energy Shield Continuous Wall Insulation and though I couldn’t tell the thickness offhand, it could be anywhere between R3.3 (0.5″) and R6.5 (1″), as I don’t think it was any thicker than 1″.
3. They didn’t run the floor insulation panels all the way to the front of the garage – there’s a gap of about 5 inches along the width of the front of the garage where they said that it’s not “worth the effort” to cut a board and place it there because they weren’t going to run PEX tube close to the front anyway. This means that there will be a lack of insulation between the slab and the ground in this area.
Am I nitpicking about this stuff? We’re spending a lot of money on this and it’ll be our garage/workshop for next 25 years, but it’s just another project for every tradesman that’s worked on it so far and things have been missed, so we’ve lost some confidence.
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Typical - they are concerned with doing the job fast, don't understand the physics of heat loss and don't want anyone telling them to do things differently. You should be able to find code requirements that require doing it right.
So these are all issues that should be addressed before the floor is poured? I've done a lot of searching and this seems to be the most promising in terms of code: is a PDF I found online (attached) on page 11. It says Saskatchewan but refers to CSA B214 which as far as I can tell is Canada-wide. Any idea if this is a code that they *must* adhere to? I've called the city's building department and left a message to see if they'd come out to have a look.
You are not nitpicking, they are ripping you off with their laziness, greed or ignorance. An order-of-magnitude estimate on what the heat loss means financially is probably in the $100/year range, not ten cents. While easily affordable, that's the extra expense every year for decades, to save a few minutes or few dollars of material today. Concrete is about R-0.08 per inch, which means it's a good conductor of heat--the edges of your slabs will be radiators conducting heat to the exterior.
1" of rigid under a heated slab it woefully inadequate. You want at least 2", 3"-4" is better. Assuming a 3 car garage, say 700sqft. Slab at 80F, soil at 50F.
With 1" of EPS you loose 5500BTU to the soil, deliver around 14000BTU to a 70F garage. So about 40% of your energy input is going to heating the earth. Very far from efficient setup. At 2" it is 20%, 3" 13%.
Micheal is spot on on the edge insulation. Slab edge insulation is much more important than insulation elsewhere. Since your stem walls are exposed to outside air, they are usually much colder so you get much more loss there. The edges should be insulated, if you want a clean finished look under the edge, have them bevel the foam so that it comes to a point near the surface.
I'm sorry if my post wasn't clear, but the floor does have 2" insulated radiant floor heating panels (https://www.amvicsystem.com/products/ampex/), the side is where the 1" foam exists.
So ultimately there will be 3" of insulation? The question then isn't about whether the 1" is adequate, but about the quality of its installation? Just making sure what we're talking about.
There will be 2” between the slab and the ground, and 1” between the edge of the slab and the stem wall.
It’s clear to me now that my initial thought was correct - the installation is inadequate. I’m open to thoughts on whether 1” is sufficient, assuming it’s installed correctly.
Before throwing around phrases like "they are ripping you off," I'd ask, what did you agree to?
How is the garage going to be constructed? A typical garage has very little insulation and a door that barely keeps the weather out. If that's the case then, yeah, insulation in the floor isn't going to accomplish much. If your intention is to build a tight, insulated building, they may not understand that. They may have heard "garage" and thought "uninsulated."
The drawings for the building included insulation in the walls and ceiling, and these were shared with them. There was much discussion around the heating options as we explained it would be a workshop, and settled on radiant heating as it would be most effective and come with lower monthly bills.
There will be spray foam in the ceiling and batt insulation in the walls. Exterior sheathing has been taped with Siga tape, we used BG73 from Conservation Technology between the foundation and mudsill, acoustic caulking, etc. Would have even used ZIP sheathing if possible but it was not within budget.
It looks like they are leaving it low just below the top of your slab so that when they finish your floor it won't have foam sticking up through the cement. You could always run it all the way up to the top of the foundation wall and then cover it(if code allows)
This is what I did with some old xps that I had.
You absolutely should have a thermal barrier between all portions of the concrete and your radiant slab. We lose so many jobs because we are unwilling to compromise on this. We are in zone 5 and do a lot of radiant slabs For houses but also for a lot of ag buildings and shops. We like
To leave our foam high so that the generals have the option to continue the foam all the way up the wall for continuous insulation or trim it off flush. You will not be happy with the way it is currently. I can’t even count how many times people decline our quotes due to cost and then call and ask us to hook up the manifolds/boiler for their DIY uninsulated in floor jobs. One guy even zip tied his loops to the rebar sitting directly on grade and then called to ask my why his boiler wouldn’t shut off. My dad, and business partner likes to explain it like a cereal bowl. The bowl is you insulation and the milk and cereal is the radiant slab. If even one drop of your cereal leaks or spills out of the bowl you have some work to do. You are spilling a lot of cereal by not insulating the top couple inches
Here are some updated photos now that they've finished - it's even worse than I noticed before. I specifically asked for them to complete the insulation on the floor and to bring the insulation on the sides up and was turned down because this is good enough and I'm overanalyzing things.
I've requested that the city's building inspector come over on Monday to have a look. Hopefully he'll say it's not up to code and they'll have to fix this.
In my area the building inspector would pass your installation without any issue as there are not any structural, safety, or building integrity issues to note. If your code requires sub slab insulation you may be able to argue that as it’s not continuous but otherwise I think you are fighting an uphill battle. I would recommend watching the concrete pour also if they start at the perimeter of your Shop it wouldn’t take much to lift foam and create a mess. I would suggest starting a couple feet in at least to get some weight on the foam so it doesnt lift the edges. At the end of the day the HVAC guy is correct - it is going to work but just not nearly as well as it could.
Lets do a bit of math.
Say it is a 700sqft garage with a 22x32 footprint. You have stem walls on 3 sides and a concrete driveway on the 4th side. Slab 6" thick.
This means 38 sqft of slab edge towards the stem walls and 16 sqft towards the driveway. Assuming pipe is 8" from the edge.
Stem walls and driveway is near outdoor temperatures, lets say 20F. Slab around 80F.
With 1" of rigid at the stem walls. You loose:
38*(80-20)/3.8=600BTU, so not much.
Lets replace that 1" of rigid with concrete. R0.08/inch, so 8" of concrete to the wall or R0.64.
38*(80-20)/0.64=3600BTU.
Driveway is similar
1" rigid 250BTU, no insulation 1500BTU.
Add the two together and you are loosing 5000BTU as is or about 1/3 of the heat output of the slab.
If you will be paying for the utilities, I would insist on slab edge insulation and a thermal break at the driveway. 1" of rigid at the slab edge and the simplest on the driveway side is a composite 2x6 on edge or a couple of composite deck boards on edge.
This sucks, but even if the contractor wants extra for this "superfluous" detail, pay it. You'll end up with a much more comfortable and energy efficient work space.
I have little hope that the company would be willing to come back out and make any changes, so I’m open to doing this myself.
I’d like to have the foam on the sides come up to the height of the stem wall and put in something with a higher R value. Would this product work?
https://www.homedepot.ca/product/owens-corning-foamular-c-300-extruded-polystyrene-rigid-insulation-24-inch-x-96-inch-x-2-inch-ship-lap-edge/1000155124
Ideally I’d be able to use this to fill in the gaps on the floor as well.
TG, that XPS insulation will work well, just be aware that the blowing agent in XPS is a potent greenhouse gas so it's better to use EPS for this situation, if you can get it.
I don't see a vapor retarder over the soil. It may not be required but it is recommended to reduce potential moisture issues.
Thank you for the reminder. The foam that’s used on the floor has a built in vapour barrier, but I’ll lay some down before I cover the patches that they left empty.
Will try to find 2” EPS.
"PEX will be 9″ away from the wall "
"there’s a gap of about 5 inches along the width of the front of the garage where they said that it’s not “worth the effort” to cut a board and place it there because they weren’t going to run PEX tube close to the front anyway."
These statements reveal a disturbing lack of understanding of how insulation works. Using the same logic, I'd ask them if they don't have any insulation in the walls and roof of their homes. After all, there's no PEX in either of those locations.
I can't tell - there is something protecting the wood sole plate from the likely to be damp concrete?
*sigh*
This is one of the things I was alluding to when I said that things were missed on this project. Turns out that the framers didn’t put any vapour barrier between the mudsill and foundation! I only found out after. I do have a 4” EPDM rubber gasket between there to prevent air leakage, but it obviously doesn’t provide coverage for the entire 2x6.
I’m open to any suggestions of what I can do to mitigate long term damage. Perhaps I should create another post.
Hi TG, Where did you get the EPDM rubber gasket? Is that something you ordered online? Thanks!
Here you go: http://www.conservationtechnology.com/building_gaskets.html
One option for retrofitting a missed sill gasket or other form of wood/concrete separation: You can loosen the anchor bolts and jack/pry up the plate and apply a liquid wood preservative like copper napthanate to the underside of the plate. This is a pain and the material is very toxic but should help preserve the wood over the years.
Should I be putting insulation in this highlighted area as well?
The ORNL "Foundation Handbook" for some standard details you can show to the contaractor:
https://foundationhandbook.ornl.gov/handbook/chapter4.shtml
That might help. Those details are not particularly builder tested and approved, they're more theoretical. But it's a start.
Your heated slab needs to be fully isolated from the structure.
This means rigid insulation between any exposed dirt and your slab as well any edges including this door threshold. You can get a door with a wider threshold to cover the rigid after the pour to protect the foam.
Make sure to anchor the foam as the small pieces can float away during the pour.
Hi Akos, Can you explain what you mean by "You can get a door with a wider threshold to cover the rigid after the pour to protect the foam."?
Also, I'm not sure if you saw my question to TG below, should I also run insulation up the wooden form they put at the end of the garage?
Thanks!
I was referring to man doors. These you can order with extended sills or pick up an sill extension such as this:
https://www.assaabloydooraccessories.us/en/products/thresholds-ramps/residential-thresholds-pre-hung/millwork-sills/ext2/
If you are looking for a thermal break for a garage door, the best is to use a piece of composite 2x6 on edge as it can handle a car driving over it.
P.S. Heated slab for a garage is no the best solution. Beside the cost, it is slow to react which makes it hard to heat it up quickly when you need it. The simplest is a budget wall mount mini split with decent cold weather performance.
I already had a boiler and I don't need the garage (workshop) to heat up quickly, I just need it to maintain a temperature of around 18C throughout the very cold winters we get here (down to -25C = -13F often enough).
Update:
I cancelled the inspection because I realized it would go one of two ways:
1. The inspector would not find any issues that go against code, and I'd have to do it myself, or
2. The inspector would find issues, I'd have to ask the company to come back and they'd reluctantly do the bare minimum, and then I'd have more of their poor work to undo while I do it properly myself.
The 2" rigid foam that I was able to find (link) turned out to be zero ozone depleting so I used that. I've attached a picture.
It wasn't perfectly done, but my goal wasn't perfection - it was doing a better job than they did and we're very happy with what we were able to accomplish with the advice and guidance from everyone in this thread.
Thank you for being so generous with your time and knowledge.
After this project is done we'll be looking for a different company to do our boiler maintenance and any other work we need done.
Hi TG - I'm working on a similar project and had question on how to detail around the garage door. What about on the other side of that wood form? Did you put insulation up along that wood edge as well? Or, did you just run the silver flat piece up to the form? Do you have a picture of how it turned out?
Hey there. Do you mean on the inside of the garage, along the foundation wall? If so, yes, I insulated that as well. I've attached pictures showing that.
If you mean whether I insulated between he outside foundation wall and the wood form - no, I haven't as yet. The driveway itself is still to be poured, so I'll add this outside insulation when the driveway is ready.
Let me know if you have any other questions. I'm more than happy to help - Conestogo Mechanical really did a poor job on this project, with the insulation, and other issues as well.
Thanks TG for sharing. I saw the note about resting a 2x6 on its side to provide a thermal break between the driveway and the garage? Is this what you plan on doing? (Will the 2x6 be visible? - I'm not sure how that detail will turn out)
What about around the other non-garage door? How did that detail work out. Were you happy running the additional foam up the sidewall? (that was 2", correct?) I was thinking of doing the same because it seems easier to manage with the concrete contractor. They can install the slab right until that edge and then I can cut it after if need be.
I will likely use the 2x6 on its side, yes. Ideally I wouldn't want it to be visible, so I'll try to position it so that around 1/2 inch of so of concrete covers it - this will mean I do lose some amount of heat but it's better than doing nothing and I wouldn't want the insulation to show.
I insulated both doors on the inside and sides the same way.
Along the entire inside wall I installed 2" foam to cover the entire foundation, knowing that this was much higher than the slab would come up to. Afterwards I just used some aluminum siding to cover the foam - nothing fancy. You can also just cut the foam down to the height of the slab after it's poured.
Hope this helps, let me know if you have any other questions. The members here were very helpful when I had questions of my own after Connestogo Mechanical did such a poor job on my radiant heating, and we get such cold temperatures in Kitchener it was a huge miss, so I'm happy to help.