Cut Grooves for Pex Tubing into Concrete Slab

dlnjapan

I'm a newbie (first timer on this forum) with a 1970s ranch style house with concrete slab. I'm itching to pull up all the carpet and install porcelain or ceramic tile throughout the house. Prior to that, however, I'd like to assess the feasibility of installing hydronic tubing in the original concrete slab. To avoid raising the floor level much, is there any reason not to cut grooves down into the concrete slab to accommodate the PEX tubing layout and then pour a minimal layer of concrete or similar material over the entire layout and then tile the floors? I know it would be labor intensive to cut the grooves, but couldn't it be done? If so, what potential problems might I run into and later regret? I am considering a solar water heating system to offset heating costs, so heat loss from slab to ground is not as big a concern, I assume. I live in sunny San Antonio, TX, where solar heat is an excellent option, and extreme cold temps are a rarity. We're more interested in hydronic heating for the comfort of not having cold tile floors in winter and for all the other benefits it provides as an alternative heating system. I'm a DIYer with a professional background in lawn irrigation, but would consider professional help for parts of the project if necessary. I would appreciate hearing thoughtful advice on the pros and cons of cutting grooves down into the existing slab. Thank you.

Jamie Hall

I can think of a few considerations

and I'm sure the radiant heating folks will come up with  more...



First, you are going to create an unbelievable amount of dust.  Like really unbelievable.  This may or may not be a consideration for you.



Second, PEX won't turn sharp corners -- so there will be additional concrete removal to make smooth corners.



Third, where is the reinforcement in that slab?  You don't want to cut through that, which may limit the depth of the grooves.

Gordy

What Jamie said

The dust could be kept to a minimum wet sawing, but then you would create an unbelievable amount of slurry...just as messy.



The slab is not insulated chances are which does not mean the radiant would not work, but means it would use more energy, and take a little more to control.



Other hidden things in the slab could be plumbing.



If you can lose an inch of head room you would be much happier with how an over the top method would function with installation, and performance. Roth panel comes to mind it insulates. its a little pricey, but all things considered it would be faster, perform much better, and give you more energy savings.through its insulation, and lower required supply water temps.



How many SF are we talking?



If you are serious about this first thing to do is a heat loss calculation radiant heat is a science. This will determine tube centers, water temps, and flow rates. Boiler size selection. Need to think about type of boiler, What fuels you have to power it. NG,LP,OIL,Electric.

M Lane

Track panels

would be my choice. Waaaaay easier than what you are talking about, worth the $ IMHO.

I'd strongly suggest bringing in a pro for the boiler/heat pump/solar design and critical parts of the installation.

dlnjapan

Head Room question

Thanks Jamie and Gordy ... very helpful feedback so far. Hadn't thought about the mess from cutting, nor the risks of hitting plumbing or slab reinforcements. If I were to abandon the idea of cutting the slab, would I really only lose an inch if I went with Roth panel? I see there are informative posts about Roth panel, so I'll research what I can here. If I were to actually succeed with a DIY installation using Roth panel, for example, what kind of ballpark costs should I expect for the whole project (just the hydronic heating system), assuming eventual connection to a solar water heating system and supplemental heat from an on-demand water heater. The whole house is 2100 square feet (one story). I assume a system could be built to allow us to turn the heat ON or OFF to certain bedrooms that are not in use for weeks at a time.

Jamie Hall

Certainly possible

to shut off parts of the system as desired.  Not really a problem, but things do have to be valved and manifolded and pumped properly to maintain proper conditions for you.  That can be a DIY project, but there's a lot to learn to be able to do it right -- particularly where you are trying to integrate various heat sources.



Costs... one of the rules of The Wall is that we do not talk costs...

Jean-David Beyer

shut off parts of the system as desired

For how long can you shut off a zone on a slab if it is really cold out? At some point, is there not a danger of its freezing? It would probably take at least a day to cool the slab a lot. But if it is a guest room or something, where for me, it is often years between guests, it could be a real risk unless enough anti-freeze is in there, or you just turn it down a whole lot, but not off.

Weezbo

another thought?

where i live in summertime, we have never ending sunlight and plenty heat.

So , what about another option,

drop the ceiling add ceiling zones add, insulation to the "Lid" , and redo the floor.

add a constant circulation type system to your "Field Side" or "SystemSide" piping arrangement , add the solar and other heat sources into the system via a "Bridge" either injection mixing or 4 way mixer ... Control for all the heat sources kept under one hat .

that way , you could do some radiant heating and pick up on the advantage of cutting down on cooling in the warmer or hotter parts of the day s ?

if you had a Garage i think ,

i would put radiant floor heat in a 1 &1/2" cap and use it as a zone that could be set for a higher temp in summers and let it absorb the heat . that way , you would not have to lose out on using that heat at night as it would gradually give back some btus it collected during the day....

well,

thats a slightly different thought ,

that could work for you ..

.........

Weezbo



*~//: )



this type of "Cooling" in summer time may not be for everyone however , there's a heck of a difference in the comfort levels ...

ceiling cooling and heating like this is the real deal ... we have a really sharp workman here on our site you might get lucky as he reads this and replies often , the best chance though is to catch him in Solar section of this site , as radiant and solar are like his really top favorites .... and if you said that you were considering using some Solar storage or whatever He would likely be quick to give you some "Under one Hat" type idea on the Caleffi parts and pieces that would make your system like the best on the planet type deal ...



hope that helps ..

Mark Eatherton

I like Weezbo's way of thinking...

Radiant floors ARE nice, but they are also expensive. Doing a radiant ceiling, when done right, CAN deliver the same high quality degree of radiant comfort, and not break the bank.



I'd do the bathroom in electric radiant floors, but do the rest in radiant ceilings.



There was a company back about 10 years ago that had a 3 HP router, equipped with a carbide blade for routing concrete floors, and they also had a saw for doing straight runs, but man, the idea of that much dust in suspension, or as Gordy said, slurry, makes me shiver. They disappeared off the market…



Professionally, I think that radiant ceilings are one of the most commonly over looked opportunities in our bag of radiant tricks.



As had been pointed out, we do not discuss pricing here, but it has to make sense that not having to run 1 linear foot of pipe per square foot of occupiable space has to be less expensive than doing a floor with a minimum of 1 linear foot of pipe per square foot of living space...



ME

Gordy

Agree

With Weez, and Mark, actually I have radiant ceilings, and floors. Can vouch for the comfort level also. Like mark says do the baths, and maybe a kitchen if going to tile the floors.



Roth would actually work on the ceiling also Mark has done this. there is also an option to do plates and strapping for this. But I like the Roth. for same reasons as the floor. That aluminum layer really lowers the water temps.

Plus with radiant ceilings you are not dealing with cutting doors, and undercutting jambs to allow for the build up.



I saw you hinted at an on demand water heater for the radiant steer clear, and use a boiler preferably a modulating condensing boiler they are made for hydronic heating.

Gordy

concrete router

Mark they probably ran out of guys who would run them. That had to be a god awful mess wet or dry cutting.......and deafening.

dlnjapan

I'm all ears ... thanks!

Appreciate all the good ideas and advice. Obviously I have a lot to learn, so I'll research some of the materials and suggestions mentioned here. I realize that DIY will be a steep learning curve, but I'm just getting started. Are there any great books and other Web resources recommended for someone attempting to build such systems themselves?

Jean-David Beyer

Are there any great books

http://www.heatinghelp.com/products/Hot-Water-Heating-Books/26/96/Modern-Hydronic-Heating-Third-Edition-br-by-John-Siegenthaler

hot_rod

concrete groover

one of the diamond saw blade manufacturers had that on the market. I think John Runke did a few jobs with one. John also made a "router sled" for grooving wood floors onsite.



A walk behind concrete saw would make short work of the straight lined, the curve was always the tough part of grooving concrete.



Grooving concrete would be my least favorite retro fit method

Gordy

I remember that

Can't remember what he used to fill in the grooves once the pex was placed.

Kevin_Jackson

dlnjapan,
I like your plan because it is pretty much the same thing I am considering.
I want to put a flexible, thin (perhaps one quarter inch or so) insulator between the foundation and the heat spreaders (the ones normally used under wood floors) and tubing. Why heat the slab at all? Especially when an existing slab has no insulation between it and the earth, that will just burn your money. So, I am looking for THAT insulator as I can't do the math without the numbers for the insulator. Any suggestions anyone?

Hey experts!
Obviously, the smaller the tubing the easier and less risky the concrete grinding will be. I've read about hydraulic erosion, turbulence and laminar flow and see that a lot of people use half inch tubing these days. Is one quarter or three eights inch tubing practical? Thanks in advance for your professional advice.

Zman

You will not get any meaningful insulation at 1/4" thickness.
3/8" tubing at reasonable (< 200') lengths will work.
Unless you own a concrete cutting business, grooving the concrete is not a great idea.
Any of the suggestions above will work better.

hot_rod

Uponor offers a 5/16" tube for the QuiK Trak system. They push lengths to 250'.

http://www.uponorpro.com/~/media/Extranet/Files/manuals/QuikTrak_InsG_9-00.aspx?sc_lang=en

AMG63

Maybe another option would be to size the area for baseboard heating. It sure would be less labor intensive as you would have far less piping to install in the existing slab.
That's how we used to retrofit old country cottages back in Ireland.

Kevin_Jackson

Thank you all for the helpful information.
Zman - The Quik Trak system hot rod suggested uses what appears to be a common approach of putting down 5/8 plywood at R-0.78 or 3/4 plywood at R-0.94, those numbers don't sound great for efficiency. A hardwood floor underlayment called Floor Muffler is R-3 at only 0.08 inch thick, that's better insulation than two inches of plywood!
Using Quik Trak's 5/16" tube would require grooves in the concrete only 1/2 inch deep and add only about 1/8 inch of floor height!

Gordy

I don't buy into the floor muffler being an r 3 at that thickness.......

Zman

At just over 16th inch thick, there is no way it is an R-3.
There are plenty of funny math terms like "equivalent R-value"
Be very skeptical....

Gordy

Question. What is your anticipated finish floor?

Another question. Is this a basement, or a home on a slab?

Mark Eatherton

Above and beyond all of the concerns that everyone has correctly expressed above, my biggest concern would be carbon monoxide poisoning from the gas powered saw. I realize this conversation has taken a different bent, but for the benefit of others reading, considering and not commenting, BE AWARE of the CO DEATH potentials... I had a customer who wanted me to do this. I declined. She convinced someone else to do it for her. She regretted doing so and said she'd never consider doing it again.

ME

Gordy

They do make electric concrete cutting saws. As Mark said co is a very real hazard. Let alone the mess from either dry, or wet cutting. Fumes, Dust, or slurry take your pick. Yes there are vac systems for these. However that is a lot of grooves to cut in a concrete floor.

KC_Jones

And after all that mess and work, there is still no insulation under the slab.....

Kevin_Jackson

Hey Gordy and Zman,
I pulled the number for Floor Muffler from this page: https://www.bestlaminate.com/blog/need-know-laminate-flooring-underlayment/
If you review the table you will see other products offering surprising "R" numbers. As for the validity of that number, I don't know how to confirm the claims of any manufacturer beyond testing the stuff myself. Is "ft²*°F*hr/BTU" a non-standard unit of measure? If everybody else is using min./BTU then that number can be off by a factor of 60. Or, is everybody else using °C instead of °F?
I see what you are saying though, wikipedia says the best foams are about R-7 per inch and Floor Muffler is saying it is (check my math) 38 per inch! Vacuum is R-45 and Aerogel (pretty exotic stuff) is R-10 to R30, soooo...
Still, wood isn't really even a good insulator by modern standards which tells me it should never be used over an uninsulated slab. And I think we can agree better insulators are out there that could give much more insulation value with much less thickness.
If I can find the "right" insulation (polyurethane (PUR) or phenolic foam at R-7 per inch or R-0.875 per one eighth inch - a little better than five eighths of an inch of plywood) and use a small diameter tubing, I might be able to do this in 5/8"-3/4" height overall which is probably short enough that I could go without concrete grooving - yea!
Additionally, I expect to use under-wood-floor style heat spreaders on top. Because I am not heating the slab, I won't get the horizontal heat spreading the slab would have provided. So, only the space under the pipe will have thin insulation to the slab, between the heat spreaders and the floor, more insulation will be needed to fill the pipe sized gap - 3/8" PEX is 1/2" diameter, ouch!
I feel so much better thanks to you guys' help, I think you have guided me to a far better approach. Okay, lay down; vapor barrier over the slab(?), 1/8 inch insulation over floor, 1/2 inch insulation with spaces for the tubing, heat spreaders into the tubing spaces then tubing into the heat spreaders for a total thickness around 5/8". Please throw more rocks at my ideas!

Gordy

Complete rubbish claim.

You can also say r 1 is 100% better than r 0.

For your own piece of mind google r value of construction materials. There are many comprehensive non misleading lists. They give rvalue of various marterials per inch. You won't find floor muffler, or it's material properties on those lists.

Gordy

Bite the bullet use Roth panel, sunboard, many others. Your build up will be the same for 3/8" tubing. Enough said.

Kevin_Jackson

Hey Gordy,
You're probably right, I should just accept the extra 1/8 inch. Sunboard - no, we know wood isn't too good.
The Roth panel looks great, they have 1/4" of polystyrene between the slab and the PEX and they claim R-3.7 overall. Plus you get the convenience of an engineered system.
I just need to compare that which is not discussed here between
a proper product and a homemade hack.
Thanks again Gordy, you've helped me a lot.

Dan Foley

I did this once, about 15 years ago. First and last. I won't do it again. I'm still coughing up concrete dust.

- DF
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Gordy

Silicosis what we know now that we didn't know years ago.

Skipped the insulation, or was the slab insulated?

Dan Foley

@ Gordy

From what I remember, this was a 6" structural concrete slab over the boiler room. The radiant was for floor warming of a stone floor in a kitchen remodel. Downward loss was minimal.

VinceJM

For the record: Ceiling Radiant does not compare well to floor radiant in terms of health and comfort. Keeping your head warm with radiant or upper level warm air, still leaves your feet cold in winter. But when your feet are warm, you can comfortably breathe cooler, healthier air at head level.

Grooving concrete has some of the disadvantages mentioned above including mess and silicon dust which can be controlled with wet sawing. Wet sawing makes lots of messy slurry of course.

I saw comments about thermal efficiency that I can't agree with though. A concrete pad directly in contact with hydronic tubing can make for a very comfortable and efficient set up. The thermal capacitance of the concrete provides great temperature stability and emergency passive heat for many hours if the power goes off.

Very important to insulate the outdoor edges of the pad though. Heat transfers extremely slowly from the pad down through the earth, but very quickly out the edges if not insulated. The heat that is stored in the concrete and the earth underneath it, tend to rise back into the building if the heating system fails.

Final thought. Plan for good access to the header that terminates your multiple runs through the floor. When cutting grooves you must either cut in a rectangular opening for the tubing to terminate into header, or do the same thing in an enclosure above floor level. You will use this to find leaks, turn loops on and off, manipulate your sensor system, etc. It may even work out best to put a rectangle at both ends of the runs to allow for bending each loop.