Need advice on installing in floor heat in garage

scott w.

Garage floor cast iron drain pipe disinegrated & plugged. Going to remove old concrete basement garage floor and and install infloor hot water heat and remove enormous cast iron rad hanging from ceiling.Also will replace 90 year old cast iron sewer pipe under garage. Contractor wants to use COMFORT TECH R FOIL ultra CB for insulation. From reading past posts most everyone on "The Wall" advises using the foam board. Looking up the R factor on Comfort Tech web site it says this product has an R factor of 17.

Question 1: Using Comfort Tech R Foil, will this be a mistake? Contractor also said this would act as a vapor barrier??

Question 2: Would there be energy savings by removing the large cast iron radiator (installed 1928) in the ceiling of the garage and adding radiant floor heating with a seperate thermostate?? The garage rad is at the very end of the hot water two pipe system. Previous remodel projects added radiant heated floors to kitchen and bathrooms.

After reading various posts regarding insulation under concrete floors I am thinking the foam board would be the better way to go. Need advice on Comfort Tech product.

GroundUp

R foil is about equivalent to putting trash bags under your slab- completely worthless from an insulation perspective and nowhere near R17 or even 1.7 for that matter. If it's not high density foam, it's trash. Use a good 4 mil poly under the foam board for a VB and you've got a foolproof thermal break. Heat loss of a space is the same regardless of heat emitter, but with a rad on the ceiling it's likely that you've got a considerably warmer temp at the ceiling vs at the floor- so by switching that around you may be able to lower your average air temp and therefore use less BTU, assuming everything else remains the same

CMadatMe

CoverTech R-Foil carries a 25yr warranty and will provide the necessary R-Value for an under slab application. Someone needs to tell Ground that in radiant we are controlling the heat loss of all objects in a room so air temps are irrelevant. Yes the surface temp at the ceiling will be warmer than the floor surface temp but you can overcome the rooms heat loss. Will it be as comfortable as utilizing the floor? No.

Zman

It looks like the manufacture is claiming a whopping R1.1 for underslab installations. https://rfoil.com/media/R-Value-Application-Airspace-Requirement-Guide-HVAC-Feb-2018-1d.pdf
Do yourself a huge favor and pay a little extra for foam.

Zman

Also, be wary of "Effective" or in this case "R-value/benefit" ratings. They are made up numbers, plain and simple. The R-17 for floors is straight-up fiction. The R1.1 is suspect. Look for products with ASTM or other recognized certifications.

scott w.

Thanks for the info.......where should I go to educate myself on the proper way to insulate and use the proper materials. Have read some discusions on proper thickness in mills for a vapor barrier. The discusion had a bit of controversey on the thickness and specs as well as various types of foam board. My garage floor replacement and adding in floor heat will not be cheap. I really want to do this project the correct way.

Zman

The building codes will give you guidelines that are focused on you climate zone.
At a minimum, use R-10 under the slab and on the slab edge. You will want a closed-cell product with a minimum compressive strength of 25 PSI. For the vapor barrier, 6mil poly should work well.
2" of Dow Blueboard or similar product will do the trick.

Ironman

CreteHeat board is our product of choice for slab radiant. It comes in 1, 2, or 3” insulation thickness. It holds the tubing down in any multiple of 3” spacing; it’s the insulation, vapor barrier and support all in one. Not cheap, but a real time saver and quality product.

hcpatel78

2" foam board. We are here in NJ and I can see clearly two garages have vast difference in temp. One with foam board one without.  Both has same footprint and location is side by side. So go with better thicker foam board , you won't regret it later .

mattmia2

Zman said:

Also, be wary of "Effective" or in this case "R-value/benefit" ratings. They are made up numbers, plain and simple. The R-17 for floors is straight-up fiction. The R1.1 is suspect. Look for products with ASTM or other recognized certifications.

I think a sheet of plywood is around r1 so the 1.1 is probably true.

mattmia2

Make sure you insulate the perimeter as well.

scott w.

Mattmia2, when you say insulate the perimeter, do you mean insulate the edge of the basement wall where the poured concrete slab will touch the wall? If my understanding of this question is correct, then do you bring the insulation up the wall to the top of the concrete slab?

Say it is a six inch concrete pour, do you bring the insulation up the wall six inches to the top of the concrete? That doesn't sound like the correct way in my thinking as you would have insulation showing around the perimeter of the floor. Do you insulate 4" high up the side wall and then have two inches above the insulation in contact with the wall? This gargage is in the basement so two of the garage walls are exterior and the base perimeter of these two walls are ten feet undergound.

The process of adding radiant heat in a concrete pad is new to me. I did gypcrete pours previously in the bathrooms and kitchen floor during renovations so please excuse me if these come off as really dumb questions. This will be an expensive project and I want to do it the proper way.

ONE More Question: The kitchen directly above the garage is radiant heated with a 3 or 4 inch gypcrete pour. The very very large and heavy 8 section radiator is suspended from the ceiling in the garage tied to 4 joists by metal straps. Each of the 4 joists has two straps and the radiator hangs direcly in the center of the joists. The joists are 14 feet long. The house was built in 1928 so these joists are 90 years old. If the weight of the heavy radiator is removed from those 4 floor joists will the floor above start to flex upwards? I have a tile floor above and do not want to risk cracking the floor. We used 3/4 tung and groove plywood sheets screwed to the floor joists when preparing for the kitchen radiant floor. Should I just disconnect the garage radiator hanging from the ceiling and leave in place after the radiant heat is installed in the garage???????????

Will post a picture later of this monster radiator.


Thank you to all the previous posters for the info. Will have a discussion with my heating professionals about the Comfort Tech R Foil.

scott w.

Here is a photo of the monster radiator hanging on the garage ceiling.

scott w.

Was wondering how those old dead men got that thing in place in 1928?

Paul Pollets

The proper method is a vapor barrier, 2" R10 foam board with perimeter insulation; 6"x6" welded wire mesh and the pex tubing tied to the mesh. The suspended radiator's supply and return could be used to supply the new radiant manifold if the S&R can be piped with a mixing valve.

hot_rod

Paul Pollets said:

The proper method is a vapor barrier, 2" R10 foam board with perimeter insulation; 6"x6" welded wire mesh and the pex tubing tied to the mesh. The suspended radiator's supply and return could be used to supply the new radiant manifold if the S&R can be piped with a mixing valve.

To add to Pauls suggestion. if possible elevate the tube into the pour. The tube should be incased in concrete and about 2" from the top surface. I poured a shop this summer and used small blocks of the 2" foam to elevate the wire mesh.

With a 4" slab, tube lying at the bottom increases downward loss by about 10% and would need about 8° of warmer SWT to get the same output. Not a huge deal unless you are looking to cover the load with the lowest possible SWT. Condensing boilers and heat pumps appreciate the coldest possible return

scott w.

Thank you everyone for the informative information. Very helpful when approaching the heating firms and asking the appropriate questions. Should have posted the huge rad on the ceiling of the garage when I first posted.

kcopp

Radiator is Really Cool... That would be great as a wall radiator in a commercial space. ipefully it can be re-used.
Where is this?

PC7060

Regarding the removal of radiator and impact of tile floor; did you use decoupling layer did you use under tile? Decoupling layer such as concrete backer underlayment or Schulter Ditra should help mitigate risk of grout cracking. 

How do you plan to remove the unit? Seems like a hydraulic platform lift would be the safest way to proceed. 

hot_rod

I'd leave that radiator up there. To keep the building from blowing away

scott w.

LOL, Hot rod, If you would see the big pile of bricks above the rad, "the house ain't going no where"!

When the stone was put down in the kitchen I thought about using the Schluter system. Had the stone installed right over the gypcrete. Shoulda, woulda, Coulda.

The big rad is located south of Pittsburgh, Pa.

leonz

scott w. said:

Garage floor cast iron drain pipe disinegrated & plugged. Going to remove old concrete basement garage floor and and install infloor hot water heat and remove enormous cast iron rad hanging from ceiling.Also will replace 90 year old cast iron sewer pipe under garage. Contractor wants to use COMFORT TECH R FOIL ultra CB for insulation. From reading past posts most everyone on "The Wall" advises using the foam board. Looking up the R factor on Comfort Tech web site it says this product has an R factor of 17.

Question 1: Using Comfort Tech R Foil, will this be a mistake? Contractor also said this would act as a vapor barrier??

Question 2: Would there be energy savings by removing the large cast iron radiator (installed 1928) in the ceiling of the garage and adding radiant floor heating with a seperate thermostat?? The garage rad is at the very end of the hot water two pipe system. Previous remodel projects added radiant heated floors to kitchen and bathrooms.

After reading various posts regarding insulation under concrete floors I am thinking the foam board would be the better way to go. Need advice on Comfort Tech product.

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Don't you mean it is a two pipe steam system??

You have a heating system in the garage that has worked since 1928; why not add to it to increase the heat transfer in the garage and avoid hacking up the garage floor??

It would be prudent to have the plumber check for proper drainage of the hanging radiator return pipe as well.

You can have the floor drain repaired by using CIPP liner for the floor drain pipe.
Your plumber may be doing CIPP pipe lining or I am sure he or she knows who does.
CIPP is Cured In Place Pipe repair and it is very easy to do.

The pipe is inspected with a video camera and then cleaned and the CIPP liner is installed and either steam cured to line the pipe or light cured to cure the liner and your garage drain is back to being a full drain without hacking up the floor and making a much bigger mess.

ratio

ISTR that metallic paints reduce the radiant portion of the heat emitted from a radiator. You should get a bump in output by painting the bottom of that with a non-metallic color.

Ah, yes: https://heatinghelp.com/heating-museum/does-the-color-of-a-radiator-matter/. According to this, metallic paint is worth about 50% of the radiant output, which is c. 1/3 of the total heat output. Not sure what the effect of horizontal ceiling mounting would have.

scott w.

The cast iron pipe to the floor drain is just gone. Tried to open it and made the problem worse. Nothing but mud and the drain snake just could not find the pipe. Want to install two drains anyway, one in each bay. The radiant floor can be controlled by a thermostat and be set at a low temp and the garage will be much warmer that the rad on ceiling. I am guessing radiant floor should save energy cost.