Radiant instalation over existing concrete slab
Last Post 31 Mar 2015 08:15 PM by BadgerBoilerMN. 14 Replies.
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karwasUser is Offline
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03 Mar 2015 03:33 AM
Hello, I am a new member to this board, and I am amazed by the quality and amount of information one can find here.

I am currently working on the project located in Northern California, with moderate climate (CZ4).

I am also living here in one of those Eichler houses with radiant heating installed originally in uninsulated concrete slab
by embedding copper loops directly in the concrete with no zone control, ancient and inefficient 60000BTU gas boiler,
and despite of total inefficiency of this system I would never switch to forced air heating.

I am providing those details simply because I want to point that in this particular area I switch on
heating maybe 10 times in a year, so optimizing this system and replacing any of its component
is not economically needed.

On the other hand, in the new project, which is actually another Eichler remodeling/rebuild,
I also plan to install radiant heating, this time with more modern approach to component
selection and installation methods.

I have setup for me several objectives: 1
) Multi zone control
2) Quality and simplicity of installation
3) Durability and serviceability of installation

High efficiency at cost of complexity of installation is not on that list.

The building has an existing slab (with copper tubing of original radiant heating still in place,
but destroyed beyond possible repair) and all framing was done with an assumption
that I have 2" of available space over existing slab.

I was considering either placing new PEX tubing directly on existing slab,
and then over pouring 2" of lightweight concrete over it, or using some prefabricated panels.

Here is the question: What options do I have for those panels?
1) Warmboard
2) Roth
3) Rehau 
4) Something else?

Based on my objectives and the fact that I have already accepted all negative consequences
of direct overpour on top of new PEX loops, is it really worth to spend nearly a $10 per sqft for such panels?
I was tempted to use them for simplicity and "neatness" of installation, but then I have realized that
I will still need to deal with an issue of custom runs for return runs to manifolds
(I have no joist space to run returns under floor, so even with an elegance of the warmboard
installation I will need to route several channels manually anyway...)

Also, I don't feel comfortable with wood placed directly on existing concrete,
although it seems to be "dry". I found no condensation under a polyethylene film
taped for several days. Do I have some other reasonable option for vapor barier,
with some insulating properties as an added bonus? If so, I would consider using
it between current slab and an overpour.

In case I will mount PEX directly on top of existing slab and then overpour,
what kind of mounting hardware / installation systems would be helpful
with neat installation?

Please advice, Przemek
karwasUser is Offline
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03 Mar 2015 03:36 AM
Off topic: How do I format or at least preserve line breaks in this system?
ICFHybridUser is Offline
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03 Mar 2015 08:43 AM
You have to change the settings in your browser.
karwasUser is Offline
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03 Mar 2015 01:38 PM
Posted By ICFHybrid on 03 Mar 2015 08:43 AM
You have to change the settings in your browser.


I couldn't find such option on Mac neither in Chrome nor in Safari,
so I have switched to IE in VMWare to finally get a full editor.
SerenityUser is Offline
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05 Mar 2015 03:55 AM
Are you anywhere close to the Highlands in San Mateo? We have worked on several Eichlers here by cutting and placing new tubing directly in the existing slab.
jonrUser is Offline
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05 Mar 2015 08:12 AM
Tell us more about placing new tubing *in* an existing slab.

karwas: Consider just moving to a radiant wall or ceiling.
greeninsulationUser is Offline
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05 Mar 2015 08:29 AM
Check out www.barrett-inc.com/creteheat.php   1 " is made just for this application of putting radiant over existing concrete floors and for snowmelts


BadgerBoilerMNUser is Offline
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05 Mar 2015 05:19 PM
There are many ways to install a radiant over-pour.

I am sure Sailor will fill you in, even though she has never, nor will ever do such a thing.

I would start with a radiant specific room-by-room heat load and end with a condensing boiler or water heater burning NG if available.
MA<br>www.badgerboilerservice.com
SerenityUser is Offline
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05 Mar 2015 11:28 PM
Installing new tubing in an existing slab involves saw-cutting grooves into the slab, just deep and wide enough to lay down the tubing. The groove, with the tubing in it, is then filled back up with lightweight concrete. Main advantage is that you don't raise the floor height.
Blueridgecompany.comUser is Offline
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07 Mar 2015 12:28 PM
What you describe is fairly straight forward.
The fact you have 2 inches to work with is great, provides options for insulation, supply return lines and a heat mass on top if you chose.
What is missing from your description is finish floors, what you see in the end of the day.
For instance if you use a floating wood floor you are home free, there are multiple solutions.
If you chose to have the topping pour be the finish floor, then you're going to have trouble squeezing in much insulation.
If a nail down floor than you need to consider sleepers, or floor panel system of some sort. Still with 2 inches you would have room for 1" rigid foam.
If Tile then you could again go with insulation and a topping pour followed by an isolation membrane (crack control) between new slab and tiles,
Dan
Dan <br>BlueRidgeCompany.com
karwasUser is Offline
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30 Mar 2015 06:02 PM
Thanks for all the suggestions.

I am leaning toward crete-heat 1" insulated panels, but it would add more than 2" over existing slab.
I hope I will be able to manage somehow with this increased floor level. My biggest concern is that
seal level for sliding doors will be below finished floor, and I had already placed an order for doors.

Przemek
greeninsulationUser is Offline
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30 Mar 2015 06:08 PM
Great choice Przemek, the sample is on its way to you. Callie
www.barrett-inc.com
BadgerBoilerMNUser is Offline
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30 Mar 2015 07:41 PM
I am guessing your ground temperature rarely goes below 60°F.

http://www.epa.gov/athens/learn2model/part-two/onsite/ex/jne_henrys_map.html

And your design water temperatures never above 80°F, which would would lead me to believe that insulation is optional and very little if at all is needed in a pour-over installation.

Proper room-by-room heat loads would be the only reasonable way to tell for sure.
MA<br>www.badgerboilerservice.com
NRT.RobUser is Offline
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31 Mar 2015 01:31 PM
I disagree that insulation would be optional... for mass alone you will want a thermal break, especially in a mild climate where you are oscillating from heating/no heating a lot. But a 1/2" of standard rigid foam might do the trick, with 1.5" for overpour thickness typical. I've seen some people do 1" overpours with 3/8" pex on tight centers and haven't heard any horror stories about it yet, but I don't know how advisable it really is.

What is your choice for floor finish? If it's hardwood then warmboard-R over 1/2" insulation would keep you right about 2" of total height, give you the downward thermal break and would be a fast responder which is good for marginal heating use, probably better than overpour if you aren't going to stay in deep heating for long every winter. You might be ok with a "lesser" panel as well if your loads are low enough but they would need to be calculated to know for sure.

If it's tile, then Roth would allow you to do thicker insulation (I'd look at the 1" thick variant) which is nice, but I don't like Roth under wood unless you're using sleepers and that's a PITA.
Rockport Mechanical<br>RockportMechanical.com
BadgerBoilerMNUser is Offline
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31 Mar 2015 08:15 PM
Ok, I'll give you your 1/2" and raise you a 1/4" with RauPanels and any floor covering thin enough to satisfy...

We would have to look at the loads and naturally mandate out door reset for the heat source.

1" is outrageous :-).
MA<br>www.badgerboilerservice.com
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