Radiant installation over a slab

Unknown

You know, the people in Vermont that say we do it wrong?

The one with the Open Systems (where legal)?

JudeNY

Radiant installation Over a slab

I will be installing radiant heat over a slab. I am planning on using Thermofin and would like any opinions/comments about the approach I am planning and any ideas on how to attach the fin and ply to the slab.

The plan is from bottom up, slab, 1/2" foil faced isocyanurate, Thermofin-C, 7" wide (3/4") ply sleepers over the flanges, 3/4" wood finished floor.

Andy N._3

easy now

The common goal here should be to help this person install a radiant system that works well. If someone gets shunned because they purchased their tubing from a less than helpful company, then are we any better than them? The advice here on the wall is free. The best in the business hang out here. Help build the radiant industry and it will be better for everyone.

sorry, just my opinion

JudeNY

I have not purchased anything from anyone yet and I wasn't aware of any restriction on questions based on who I was purchasing from. I am still gathering information. I'm asking the question here because I've heard there is a lot of experience on this site. Dale Pickard contacted me in response to an earlier question I posted here which is how I became aware of Thermofin.

Can anyone comment on my original question ?

hot_rod

One method

I have used is to fasten plywood strips to the concrete. For this I use both construction adhesive, and concrete nails or screws (tapcon) If this is a large area a p[ower nailer is worth the rental fee. It takes a special tool to shoot nails into concrete. Most tool rental plaes have them.

The strips would be nailed according to the design requirement. Often 12" oc is adequate. Your design will tell you this.

For above slab I prefer the U shaped fins. With these I forst fasten the plates to the plywood strips, then insert the tube. The finished floor covering will determine the next step. Hardwoods can be nailed or floated directly on the strips. Tile, stone, etc would next need a cement backer board application.

Carpet or glue down would require an underlayment like 1/4" plywood. They make products specfically for underlayment.

These are the methods I have used sucessfully for many years.

Check with your lumber supplier. The home centers and many lumber yards will rip those plywood strips for you. Often at no charge. That will save you one time consuming step.

Did you get a copy of the Floor Covering Guide from the RPA website. This has tons of info.

hot rod

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JudeNY

Thanks hotrod. That was the method Dale suggested but after getting the samples and doing a mock-up I saw two potential problems.

One was that with the U fin above the sleepers there is not a level surface to nail the finished wood floor to. The wood floor over each fin will be higher than the 4" ply nailing surface by the thickness of the fin. Is this a problem for my finished floor ?

The other is that I'm concerned that the tubing does not snap tightly into the U-fin Dale sent and the finished floor will be rubbing against the pex. Is this a problem for the tubing ?

radiant

radiant over slab

hey jude,
take a look at this. we have installed these panels directly over slabs with nothing but a vapor barrier between. check this old house archives they have just recently done this in the WInchester MA project and the dream kitchen in Chicago.

hot_rod

You would have the same

issue with the plates UNDER the strips, as far as the flushness!

This is my most recent U-Fin job. The remodel contractor installed the strips, and the U-fin. I installed the tube and made it all work. This is Wirsbo MultiCor PAP. The kitchen sink is on an outside wall so I ran one loop under the cabinet to protect the water lines from freezing.

The owner purchased the plywood from Home Depot. They will make 4 cuts per sheet for free, and deliver! So the strips came to the job 12" wide 8' long. (use plywood, or Advantech subfloor material for best nailing of the hardwood, stay away from wafer or particleboard products)

The carpenter used a small portable table saw, on the job, to relieve both edges of the strips to allow the plates to fit flush with the top of the plywood. 3/4" cherry T&G strip flooring was nailed directly over the plates.

This is a fairly simple, straight forward install. Well within the means of anyone that can safely weild a hammer and saw

I have priced every "on top" system out their. Using carpenter labor, or homeowners, this system comes out the best. Both dollar wise, and by far performance wise.

I use PAP for a tight fit, and have never had a problem with fit, or noise. The slightly larger od and much smaller expansinn rate, combined with ease of install, makes PAP a perfect tube choice, in my opinion. Heck you don't even need an uncoiler. Throw a coil on your shoulder, use your foot to form and push it into the grooves. I then take a rubber mallet to set the tube home.

hot rod

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JudeNY

hotrod, thanks for the great detailed description.

Is the reason you were able to do 12"oc rather than 8"oc because the fin is in direct contact with the finished floor ?

PAP sounds like it would be good for me to work with. This is the first I've heard anyone mention it and I have been unable to find any info online, even on the Wirsbro site. Is it not widely used because of expense ? Is it equivalent to 1/2" pex in terms of sizing ? Do you know the bending diameter ? Do you know where I could find specs ?

I will be doing 2 rooms, one zone and the second room will be between the joist installation with C-fin. Can I use PAP for one room and pex for the other or should I be using the same tubing throughout ?

And thanks for directing me to the RPA site. I have spent most of the day there.

Riles_3

Wirsbo Multicor \"PAP\"

has a slightly lower List Price versus HEPEX.

hot_rod

Jude

12" oc worked to meet the heat loss in my case. Really you should do a heatloss estimate, regardless of the size of the project. This will tell you the necessary tube spacing, and lots of other info regarding temperature, loop length, etc.

Certainly going to 6 or 8" oc doesn't hurt, and in bathrooms I prefer the tighter spacing regardless of the design requirements. Mainly in slab or mudset installs to provide a nice even temperature across the floor area.

Plates 8" oc should give you a nice even temperature floor without stripping.

Lots of manufactures offer PAP tubes now. Kitec is another manufacture that has offered PAP for many years. In my area it is by far the "price point" brand

I like the Wirsbo MultiCor and Weil Alumpex, they may be made by the same manufacture, actually. Higher cost, but they seem to have a tad thicker alumuminum layer and less kink prone. In the end they all work fine for transfering heat:)

I have a few brands I prefer to work with, in my area it's more an issue of what is available locally or the quickest. As often I only have a few days notice to get the job installed.

I would say, at this point, you are ready to "pull the trigger" on your job. Any remaining questions will probably answer themselves as you gather pieces and get down to the install. Good luck.

hot rod

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JudeNY

Thanks hotrod