PEX Tubing in floor

[tankd0g]

Hi, can anyone tell me what considerations you have to make when putting PEX into your poured slab? Do you have to go thicker than 4 1/2" to accommodate it? I want to pour a 24x24' and put PEX in for later on when I can afford to install solar panels. I will have a 4 poster lift in the garage so I expect I will probably have to avoid the footprint of the lift legs.

 

[koditten]

I'm willing to geve you pointers. I see you have 1 post. Are we never gonna see you again? I've responded to many people, just like you and never hear from them again.

I want to respond, but frankly i worry. Tell me you are earnest and I am wrong. I love to talk about my infloor heat system.

Hope to hear from you.

Later

KO

 

[Burl]

My system is a bit larger than youors, 30 X 32, was done in 2 pours, is no thicker than 4". In my opinion the key to a successful working system is the insulation board under and around the slab, as this keeps the heat from going into the ground and walls. I wouldn't cheap-out in this area. As I stated, mine was done in 2 sections, with two different loops in each section. That way, if something happens to a tube in one loop, I have a second back-up. Lots of good info on this site, good luck with your project.

 

[Higgins]

We installed 3/4" PEX, and the local inspector asked us to bump the slab to 5"

AL

 

[tankd0g]

I have an existing 24x16' garage with a 5" slab on 1 foot of graded 7/8" split gravel, that has not cracked in 8 years but it has no PEX in it, I know that general consensus is to use tamped class A or smaller gravel but the loose 7/8" packed up well and didn't sink in my soft ground. Strength of the floor is my only concern with putting the tubing down because I will have two cars on a lift more of less in the middle of a 24' slab. Can you lay the foam over gravel or do you need to have a billiard board smooth surface to put it on? I could see any void under the foam becoming a problem later.

 

[tankd0g]

I'm willing to geve you pointers. I see you have 1 post. Are we never gonna see you again? I've responded to many people, just like you and never hear from them again.

I want to respond, but frankly i worry. Tell me you are earnest and I am wrong. I love to talk about my infloor heat system.

Hope to hear from you.

Later

KO

I just got here I wish this forum was around when I built my first garage, I made a lot of mistakes. I hope to get this one right the first time.

 

[Randy in Maine]

Generally a lift requires a bit thicker concrete (like on the order of 6") and that is what mine is. I used the 4000 psi concrete also 2" of insulation under the slab. You probably don't need rebar in there if it is an "at grade" type slab, but a well compacted base made of suitable mateiral is really a requirement.

I used 1/2" PEX myself. (1000 linerar feet in a 1120 square foot building). My lift guy told me to not put any tubing within about 3' of where the posts go for the lift. I also did not put insulation under the 2 post areas and gained 2" more of concrete there.

 

[Higgins]

They recommended 2" Pink around the foundation, then 1" inside that, and nothing in the middle!

So to make things simple for me, I just did 2" foam for the entire floor. That way I didn't have to worry about leveling out the gravel to match the foam thickness! And was real quick to put down.

Now putting the PEX down was another story!!!!

AL

 

[finn]

My inspector insisted that we add perimiter insulation in addition to the under slab insulation. He also required that we pressure test the system before and after the pour.
I've had the PEX in for about 9 years now but have yet to hook up the control panel or boiler.

Life got in the way....maybe this summer.

 

[tankd0g]

Generally a lift requires a bit thicker concrete (like on the order of 6") and that is what mine is. I used the 4000 psi concrete also 2" of insulation under the slab. You probably don't need rebar in there if it is an "at grade" type slab, but a well compacted base made of suitable mateiral is really a requirement.

The manual for the lift calls for 4 1/4" 3000psi concrete with rebar. I was planing on going 5" with the PEX tubing, I assume the volume of the PEX will mean that it's not actually much more concrete. I suppose it couldn't hurt to go 6" though.

 

[Higgins]

Our PEX was installed as a future option!

We did presurize the system 48 Hrs prior to the pour, and left it pressurized during the pour, just in case someone punctured the PEX!

Should you install a PEX system, make sure you have a "Patch Kit" available during the pour just in case!

AL

 

[bgarrett]

I'm willing to geve you pointers. I see you have 1 post. Are we never gonna see you again? I've responded to many people, just like you and never hear from them again.

I want to respond, but frankly i worry. Tell me you are earnest and I am wrong. I love to talk about my infloor heat system.

Hope to hear from you.

Later

KO

Even if he never comes back there are lots of us reading this thread, hoping to learn

 

[Randy in Maine]

The manual for the lift calls for 4 1/4" 3000psi concrete with rebar. I was planing on going 5" with the PEX tubing, I assume the volume of the PEX will mean that it's not actually much more concrete. I suppose it couldn't hurt to go 6" though.

I don't know what concrete goes from up in NS, but here in Maine I pay about $120 a cubic yard since we really don't have much limestone here. One a small garage like you have, the money would not be a huge change. The only problems with a 24x24 garage is that you don't have a lot of room to work around the cars when they are in there. My garage area is 28'x28'x12' tall which helped out on my tiny litle lot at the beach. I do have a woodshop on the side of it that is 12' x28' x 12' on the same slab.

Think of it as "more thermal mass" to store heat (as I send you those snowstoms every other week this last winter).

 

[tankd0g]

I don't know what concrete goes from up in NS, but here in Maine I pay about $120 a cubic yard since we really don't have much limestone here. One a small garage like you have, the money would not be a huge change. The only problems with a 24x24 garage is that you don't have a lot of room to work around the cars when they are in there. My garage area is 28'x28'x12' tall which helped out on my tiny litle lot at the beach. I do have a woodshop on the side of it that is 12' x28' x 12' on the same slab.

Think of it as "more thermal mass" to store heat (as I send you those snowstoms every other week this last winter).

I would like to go bigger than 24x24' but to go even one foot bigger here requires an engineered slab with a 4' footer, stamped engineered plans, inspections and basically increases the cost to build by 40%. That's why I am going with a single bay, 12' ceiling and 4 post lift so I can store both cars when I'm not using the lift and have room on either side to work.

 

[wedge40]

Here's my 2 cents and couple of questions.
4 1/2" is fine, I think. Are you going to put mesh or rebar in the cement? If rebar take into considerationt the rebar thickness etc when planning. 1/2" rebar crossed ontop of each other uses up a 1" of space. I went with 5" and rebar and ran into problems, because with the rebar and pex, I kind ran out of room to use rebar chairs. The advantage of rebar or mesh is you have something to tie the pex to. I would also mark the location of the runs along the side and take lot of photos. Are you going to bolt the 4 post lift down? If so then figure out where the bolts will be and work the pex around it. There is a program called loopCAD that you use free for 30 days. I thought it was worth the download.
Good luck with the project. Hope you stick around and are willing to post photos of your progress.

Wedge

 

[tankd0g]

Here's my 2 cents and couple of questions.
4 1/2" is fine, I think. Are you going to put mesh or rebar in the cement? If rebar take into considerationt the rebar thickness etc when planning. 1/2" rebar crossed ontop of each other uses up a 1" of space. I went with 5" and rebar and ran into problems, because with the rebar and pex, I kind ran out of room to use rebar chairs. The advantage of rebar or mesh is you have something to tie the pex to. I would also mark the location of the runs along the side and take lot of photos. Are you going to bolt the 4 post lift down? If so then figure out where the bolts will be and work the pex around it. There is a program called loopCAD that you use free for 30 days. I thought it was worth the download.
Good luck with the project. Hope you stick around and are willing to post photos of your progress.

Wedge

I do plan to do mesh and rebar, it worked well on my first garage so I'll stick with what works. How close together did you run your rows of PEX? Fortunately the lift is free standing and has casters so I don't have to worry about anchor placement. I did a rough drawing of the exterior as you can see in my avatar, using Google Sketchup. I haven't done the detail for the interior yet.

 

[gpalmer77]

I do plan to do mesh and rebar, it worked well on my first garage so I'll stick with what works. How close together did you run your rows of PEX? Fortunately the lift is free standing and has casters so I don't have to worry about anchor placement. I did a rough drawing of the exterior as you can see in my avatar, using Google Sketchup. I haven't done the detail for the interior yet.

I did a similar sized slab to you (22x24)..... laid my mesh down on top of the insulation, then zip tied my Pex to it in two loops about 200 ft each. One 6" spacing at the wall, then one 9", then 12" all the way to the center. My rebar went on top of the Pex. The crew lifted the mesh when they poured. Ended up about 5" thick of 6 1/2 bag mix, 4000 psig. I plan on installing a four post lift also.

 

[ixlr8]

I have a 30x30 shop, I put in 4 loops. Near the edge of the slab they are 9" apart, the rest are spaced 12"-15", I attached them directly to the foam with "foam staples", put the rebar on top of the tubing. I have 4" of 3000psi cement, so far no issues with my 4 post lift... then again it has only been in for a week. BendPak recommends a minimum of 3.5" of 2500psi concrete.

 

[wssix99]

I'm going through this now for my house/garage, which will hopefully start this summer...

Hi, can anyone tell me what considerations you have to make when putting PEX into your poured slab?

The big ones are:
- Insulation is needed under the slab.
- The reinforcement and PEX need to be placed to allow the minimum cover over them. (I've seen 1 1/2" to 2" cover recommended.)

Do you have to go thicker than 4 1/2" to accommodate it? I want to pour a 24x24' and put PEX in for later on when I can afford to install solar panels. I will have a 4 poster lift in the garage so I expect I will probably have to avoid the footprint of the lift legs.

Not by much. The PEX won't do any harm with regard to the amount of weight the slab can withstand. If you are going with a two post lift or something that will create a lot of bending in the slab, you'll want the same cross sectional area of concrete. For example, if you are doing 1/2" PEX (5/8" OD) every 12", then an extra 1/32" of concrete will more than make up for the lost area from the PEX.

I will have a 4 poster lift in the garage so I expect I will probably have to avoid the footprint of the lift legs.

Yep.


An interesting thing I cam across for my PEX garage floor has been constructability. I initially planned to put the PEX on top of the rebar, centered between the bars. (I wanted to do this so my reinforcement would have full contact with the concrete to help minimize crack widths.) Since this arrangement (once the rebar was lifted off the floor/insulation) would take up my concrete guy's stepping space between the bars, we've decided to put the PEX directly on top of the insulation and then suspend the rebar above that. With this arrangement, I also won't have to worry about my HVAC contractor wanting to change the PEX spacing at the last minute. (He still has to do the calculations to figure out how far he wants to place them.)


I'

 

[tankd0g]

Thanks for the info guys, I never thought of putting the pex on the bottom, that would ensure I don't have any too close to the surface.

 

[koditten]

Will respond in detail a bit later when I get to a computer. Using the phone now and it ***** to Type one finger. Glad you are gonna be a regular remember.

Later
Kirk

 

[matouse3]

Thanks for the info guys, I never thought of putting the pex on the bottom, that would ensure I don't have any too close to the surface.

I stapled to the foam. From what I read on here and my desire to not worry when they were doing the control cuts, that's what I decided on. It was easy and relatively painless. I rented the foam stapler from blueridge.com, along with all my pex and staples and manifold. I also used chairs during the pour instead of relying on the concrete guys to pull up the wire. This gave me some confidence that the wire was uniform across the pour.

There is a layout diagram in my build thread. You probably don't need anything that complicated, but you might want to take a look.

Good luck.

 

[tankd0g]

I stapled to the foam. From what I read on here and my desire to not worry when they were doing the control cuts, that's what I decided on. It was easy and relatively painless. I rented the foam stapler from blueridge.com, along with all my pex and staples and manifold. I also used chairs during the pour instead of relying on the concrete guys to pull up the wire. This gave me some confidence that the wire was uniform across the pour.

There is a layout diagram in my build thread. You probably don't need anything that complicated, but you might want to take a look.

Good luck.

Did you stand both the mesh and the rebar off with the chairs to the same height?

 

[koditten]

As promised, I'm back to comment on my floor heat system. My 26 x 30 has 900' of 1.2" pex. I think people get hung up on the placement of the tube. As long as you keep the middle of the floor spacing at 10-12" and do the perimeter loop at 6-8" you will be fine.

As said earlier, good insulation is a must. 2" foam board on the bottom and orund the edge of the slab. I am amazed at how much heat still migrates to the soil 12" outside my structure. My roses seem to love it tho

I attached the pex to the foam board them placed mesh over the pex. This may not be as efficient as having the pex nearer the center of the slab, but the way I figure, its a shop. You will have energy losses that a home wont have. I did not use a layout program to plan my tubes, but I did use these screw in pex clamps. They just screw into the foam board and then you clip the pex in. worked slick.

I have 4" thick concret with a 2 post lift actually straddling one of my tubes. I have seen no cracking so far. I don't leave a car in it for long durations, so storing a vehicle on a 4 post may be different.

I'll try to dig up some more pics if people want.

Later

KO

 

[tankd0g]

As promised, I'm back to comment on my floor heat system. My 26 x 30 has 900' of 1.2" pex. I think people get hung up on the placement of the tube. As long as you keep the middle of the floor spacing at 10-12" and do the perimeter loop at 6-8" you will be fine.

As said earlier, good insulation is a must. 2" foam board on the bottom and orund the edge of the slab. I am amazed at how much heat still migrates to the soil 12" outside my structure. My roses seem to love it tho

I attached the pex to the foam board them placed mesh over the pex. This may not be as efficient as having the pex nearer the center of the slab, but the way I figure, its a shop. You will have energy losses that a home wont have. I did not use a layout program to plan my tubes, but I did use these screw in pex clamps. They just screw into the foam board and then you clip the pex in. worked slick.

I have 4" thick concret with a 2 post lift actually straddling one of my tubes. I have seen no cracking so far. I don't leave a car in it for long durations, so storing a vehicle on a 4 post may be different.

I'll try to dig up some more pics if people want.

Later

KO

That beats renting a gun and possibly shooting a staple through a line after the 4th beer Do you know what company makes these screw in pex clamps?

 

[ixlr8]

I used these foam staples that just pushed into the foam by hand. They do make a staple gun but I didn't see the need spend the money for one just doing my garage.

http://www.pexsupply.com/Malco-FBSN1-1-1-2-Foamboard-Staples-200-box-10396000-p

 

[theoldwizard1]

If you really are planing to someday heat the floor, insulation is CRITICAL ! 2" of foam board minimum, 4" is better.

Don't forget the heat loss at the edge of the slab. 4" down as deep as the "frost line" (48" ?)

 

[Randy in Maine]

I used these little clips to clip the 1/2" PEX tubing to the wire mesh I used in my floor. Quite handy and easy to move runs as you lay it out.....

http://www.insulationsolutions.com/products/quip/information.html

 

[goneflyin2002]

Hey Tdog, fellow Canuck-
You'll love your heated floor but I suppose a thousand guys have said that already.
I used 6" square steel mesh and tywrapped the pex to it.
Do like Wedge says and download LoopCad, it's an excellent program. I had 2400' of 1/2" pex to lay down in 9 circuits and the program figured out the layout so that each circuit was nearly the same length, important if you're using a simple manifold.
One thing's certain, you don't want to start laying out the pex without a plan!
Like everyone else said, spend some $$ on insulation under and around the slab. It's amazing how effective a mere 2" is. You only have one chance to do it. I put 2" under the whole slab and 4' down around the perimeter.
Have fun!
Don

 

[tankd0g]

Hey Tdog, fellow Canuck-
You'll love your heated floor but I suppose a thousand guys have said that already.
I used 6" square steel mesh and tywrapped the pex to it.
Do like Wedge says and download LoopCad, it's an excellent program. I had 2400' of 1/2" pex to lay down in 9 circuits and the program figured out the layout so that each circuit was nearly the same length, important if you're using a simple manifold.
One thing's certain, you don't want to start laying out the pex without a plan!
Like everyone else said, spend some $$ on insulation under and around the slab. It's amazing how effective a mere 2" is. You only have one chance to do it. I put 2" under the whole slab and 4' down around the perimeter.
Have fun!
Don

Thanks for the advice, do you mean you dug a 4' trench and slotted a piece of foam in it up against the slab after it was poured?

 

[Racecarl]

My shop is 24X30. I have 3 runs of 1/2" PEX, about 220' of PEX per circuit. My foundation wall sticks up above grade 8". When I poured the foundation walls, I put in 2" rigid polystyrene (the pink stuff) on the inside of the forms. I trenched and hand dug the foundation wall down to at least 48", since 46" is the frost line in our area. The wall insulation goes around the entire perimeter, including the 16' overhead door area.

I left the insulation 1.5" short of the finish level of the floor. This 1.5" space is occupied by a 1.5" X 2" treated board held to the foundation wall by tap-cons. I went to great pains to make sure this board was dead-on level so my concrete crew could use this board to screed and level the floor. I rented a jumping jack for a weekend and packed and leveled the dirt inside the shop perimeter to about 10" below final floor level. I then installed 2" of gravel, and laid down more 2" rigid inside the first four feet of the perimeter. The rest of the floor was covered with gravel and compacted with a plate compactor to 6" below final floor level. A vapor barrier of reinforced plastic was placed over the compacted gravel. The floor is 6" thick.

I made seven floor pulls and placed them in the floor, setting the tops to final slab grade. I made a grid of 1/2" rebar on 4' centers with 3/8 rebars placed between the 1/2" bars. To this grid I installed 6X6 wire mesh. I suspended this reinforcing grid on half brick chairs which placed the grid roughly 3" off the base. I tied the PEX to the mesh, using nylon zip ties. Each tie spot took two wire ties, one tie to tie the PEX to the mesh an the other to keep the pex from solidly contacting the mesh. My wife's cousin is a concrete contractor and poured the floor for me while I was at work, finishing the slab to a power-trowelled super smooth (easy to sweep) finish.

I am building solar panels to heat the water, but I have not completed them yet. The walls are 2X6 on 2' centers, insulated with R-19 fiberglass. The outside and inside walls are covered with 1/2" osb. The 12' ceiling is insulated with almost 2' of blown cellulose. Before I sheeted the inside, I installed a 12 mil plastic vapor barrier on the walls and ceiling. My Ranier 16X10 overhead door is R-19 and seems to be sealed well. I have four south windows, one small west window, and two north windows. All are Crestlines from Menards and are double pane.

The past two winters it has never got much below 38 degrees inside the shop. I have a 35,000 btu propane radient heater which keeps it bearable inside. I only use the heat when I plan to be in the shop for a while and I monitor my CO detector closely. I am really looking forward to getting the panels finished and putting the pex in the floor to good use.

 

[tankd0g]

insulated with almost 2' of blown cellulose. Before I sheeted the inside, I installed a 12 mil plastic vapor barrier on the walls and ceiling. My Ranier 16X10 overhead door is R-19 and seems to be sealed well. I have four south windows, one small west window, and two north windows. All are Crestlines from Menards and are double pane.

The past two winters it has never got much below 38 degrees inside the shop. I have a 35,000 btu propane radient heater which keeps it bearable inside. I only use the heat when I plan to be in the shop for a while and I monitor my CO detector closely. I am really looking forward to getting the panels finished and putting the pex in the floor to good use.

I feel like I could rebuild your shop from that description Do you have any idea what you will get out of your home built panels? I was looking at a set of 30 evacuated tubes for around $1000 that are supposed to be the peak equivalent of 1700w. To me that that's not a whole lot of energy but I don't have any experience with radiant in floor heat so maybe it's enough to keep things above freezing with the help of a hot water heater.

 

[Racecarl]

The panels will be made from some old sliding glass doors. The glass area is about 1.5 meters, so I hope to get 1200-1500 watts of energy from them. I have enough materials to build and hang up to 5 panels. I will mount the panels on a south facing awning that is set at the correct angle to maximize solar collection when the sun is at it's lowest point.

I intend to double glaze the panels--I have 17 of the sliding doors. The doors came out of a high school that was renovated recently, so all have tempered glass and anodized aluminum frames. The collector will consist of two pieces of 16 gauge aluminum sheet that will be spaced 1/2" apart. This gap will be flooded with RV antifreeze and will thermosiphon into a blue plastic 55 gallon barrel. I intend to pump the hot water from the top of the tank, down through the floor, and back into the barrel, which will then go into the bottom of the panel and get heated again.

The barrel will be in the attic, which will be about 15-18 feet above the floor. I have not got the pump figured out yet--I need to research pumps. I have considered trying to find a 12 volt pump and use a PV solar panel to power the pump. Ranchers have been doing away with windmills for these solar pumps and they seem to work pretty well--the ones locally pump water 50-100 feet out of the ground.

I am not really looking to keep my shop at 70 degrees, although that might feel good some days. If it could keep the place 60-65 I would really be happy. I need to get some other projects completed and get a prototype panel built. I can calulate the gain and figure out how many panels I need.

 

[tankd0g]

The panels will be made from some old sliding glass doors. The glass area is about 1.5 meters, so I hope to get 1200-1500 watts of energy from them. I have enough materials to build and hang up to 5 panels. I will mount the panels on a south facing awning that is set at the correct angle to maximize solar collection when the sun is at it's lowest point.

I intend to double glaze the panels--I have 17 of the sliding doors. The doors came out of a high school that was renovated recently, so all have tempered glass and anodized aluminum frames. The collector will consist of two pieces of 16 gauge aluminum sheet that will be spaced 1/2" apart. This gap will be flooded with RV antifreeze and will thermosiphon into a blue plastic 55 gallon barrel. I intend to pump the hot water from the top of the tank, down through the floor, and back into the barrel, which will then go into the bottom of the panel and get heated again.

The barrel will be in the attic, which will be about 15-18 feet above the floor. I have not got the pump figured out yet--I need to research pumps. I have considered trying to find a 12 volt pump and use a PV solar panel to power the pump. Ranchers have been doing away with windmills for these solar pumps and they seem to work pretty well--the ones locally pump water 50-100 feet out of the ground.

I am not really looking to keep my shop at 70 degrees, although that might feel good some days. If it could keep the place 60-65 I would really be happy. I need to get some other projects completed and get a prototype panel built. I can calulate the gain and figure out how many panels I need.

That sounds great, I hope you post pics when it's done. I'm probably going to buy panels but do my own arduino based controller and pump system. I was thinking of using a hot water heater as storage so that it's insulated and I have a supplemental heat source option, it's possible I'm being optimistic thinking I will need additional storage though

 

[wedge40]

I do plan to do mesh and rebar, it worked well on my first garage so I'll stick with what works. How close together did you run your rows of PEX? Fortunately the lift is free standing and has casters so I don't have to worry about anchor placement. I did a rough drawing of the exterior as you can see in my avatar, using Google Sketchup. I haven't done the detail for the interior yet.

Sorry for the long delay.
My pex is one foot on center. That seems to be the norm. As most people will tell you insulation is king when figuring out how to heat your garage.

2" below grade, 2" around the perimeter, and insulate the walls and ceiling with as much as you can afford.

Wedge

 

[tankd0g]

As I was drawing out the plans for this I ran into another question. What have you guys done to cover up the insulation on the outside of the slab? If I go 2" pink on the outside, I'm going to have more than 1" of pink foam sticking out below the siding and probably 6" or more above the grade.

 

[wssix99]

As I was drawing out the plans for this I ran into another question. What have you guys done to cover up the insulation on the outside of the slab? If I go 2" pink on the outside, I'm going to have more than 1" of pink foam sticking out below the siding and probably 6" or more above the grade.

Are you talking about where the slab extends outside the building at the garage doors? One of the challenges here is that the garage slab typically extends under the door and outside. Since I don't want to heat the outside world with my slab, I'm going to put the door flush with the wall by countersinking my 2X blocks to hold the garage door tracks and stopping the heated slab and at the wall. I'm going to have an expansion joint inside the full length of the wall, which should get my doors to overlap that by just a little bit. Outside off that expansion joint, I'm going to build my thermal break with a 2X6 standing on end and will then pour a small concrete threshold outboard of that, tied in to my foundation. I'll then put a rubber threshold on top of all that, which will better seal my garage door and cover the 2X sticking up at the surface of the concrete. (This 2X thermal break seems to be commonly used with industrial freezers - so I'll think its good enough for me. I don't want to put foam down as the break and then drive over that - although I suppose using high PSI foam, would do well.)

 

[tankd0g]

Are you talking about where the slab extends outside the building at the garage doors? One of the challenges here is that the garage slab typically extends under the door and outside. Since I don't want to heat the outside world with my slab, I'm going to put the door flush with the wall by countersinking my 2X blocks to hold the garage door tracks and stopping the heated slab and at the wall. I'm going to have an expansion joint inside the full length of the wall, which should get my doors to overlap that by just a little bit. Outside off that expansion joint, I'm going to build my thermal break with a 2X6 standing on end and will then pour a small concrete threshold outboard of that, tied in to my foundation. I'll then put a rubber threshold on top of all that, which will better seal my garage door and cover the 2X sticking up at the surface of the concrete. (This 2X thermal break seems to be commonly used with industrial freezers - so I'll think its good enough for me. I don't want to put foam down as the break and then drive over that - although I suppose using high PSI foam, would do well.)

I'm actually talking about the entire exposed perimeter of the slab. I'll have 5" of exposed concrete all the way around, plus a little more at the doors now that you mention it. I guess I could go 1" foam and flash it under the siding so that it doesn't catch any water coming off the wall.

 

[Randy in Maine]

I did not insulate the exterior of my concrete wall but used the 2" of foam on the inside to provide a thermal break from my heated floors to the unheated 8" tall stem walls.

I ran it from the bottom of the floor (before they poured the floor) and then covered it up with 1" x 12" pine to keep it out of sight and to protect it from getting all torn up. I secured the pine to the stem walls using those topcon fasteners. It came out nice.

 

[cdecker]

I poured a 24x32 slab back in 2010 (sorry, no build thread yet). I used 2" foam under the entire slab, and along the edges of the slab, 45'd to the outside surface edge. I also used 2" of foam along the entire interior perimeter of the 48" deep x 16" wide trench poured footings. We then laid down wire mesh, and my (3) loops of 1/2" pex, 12" on center were zip tied to that. I did not pressurize the system before pouring 4-5" on top of it, but have pressurized since and everything is fine. Like others, no boiler yet, so the radiant hasn't been fired up. Maybe next year...