Radiant Ceiling Installation

SENWiEco

Evening Folks,

I am FINALLY starting the installation of my hydronic radiant ceiling heating/cooling system and wanted to check in with the pro's before I got too far into the project.

I am using Uponor hePEX and Radiant Design and Supply ThermoFin U transfer plates. I am installing the plates at 6" O.C. and infilling with foil faced polyiso.

I am still trying to determine the best way to efficiently install because the first room is taking way too long and I have another 2500ft2 to get done.

Here is my current procedure:

Step 1- precut several hundred foam strips at a time
Stem 2 - use a roller to apply contact cement to one side of a foam strip to one side of the transfer plate completing a couple dozen assemblies at a time
Stem 3 - use a roller to apply contact cement to the back side of the foam of an assembly and the OSB ceiling a couple of rows at a time, let sit for a couple of minutes and then press apply two together.

The problem I am having is that the contact cement is setting up VERY fast on the foil face and if I do not roll really quick, then as I roll, it just starts to peel itself back off the foil. Really not sure why this is happening. The cement is not setting up like this on other surfaces.

I am also finding that the adhesion between the rough OSB and the foil face is not great and sometime the panels just fall off the ceiling.

So now I am also placing 3 screws (each end and middle) on one side of the transfer plate (side glued to foam) and securing to OSB (step 4).

Finally, I am finding that the contact cement is setting up quickly in my roller tray and I am having to either pour in a very small amount that only does 1-2 rows, or I end up with glue that is starting to set off and hard to roll out evenly.

This process is also taking way too long. Each couple of rows is taking at least 10-15 minutes, and these are only 8ft long rows. I have a total of 540 - 8ft plates to install. At this rate it will take me a month to install just the plates + time to cut foam strips and glue strips to plates.

So a question to those that have installed this type of system.

- Am I just temporarily holding the system to the ceiling till the drywall is applied.
- Will the attachment of the drywall (screwed 12" O.C. between each row of transfer plates) be the main support for the system?

If so, I am proposing that skip step 3 and just screw the plates to the ceiling with three screws per plate. Should I also skip step 2 and just slide foam strips under the edge of a transfer plate that I have screwed to OSB and repeat?

Thoughts?

Many thanks in advance for any direction.

Ironman

I'd recommend these:

https://www.sunboardpanel.com/

psb75

The contact cement procedure sounds like a nightmare. I would skip it and simply apply each isoboard strip and Thermofin plate one at at time with screws and call it good. Maybe put in more than 3 screws per plate--6 may be better. Three is ok--initially. Fill the rest in later. VERY careful installation of the sheetrock layer is important. A very diligent schedule of appropriate length screws, all sunk to a perfect depth (DON'T break the paper!). All of that messing around with contact cement is doing nothing structurally.

Zman

It's sounds like you just have a contact cement issue.
Contact cement does not work well on materials with rough texture as it does not make contact with enough surface area. As you are finding, the working time is a PITA.
Why not use tubes of foam adhesive? It is like construction adhesive but it won't eat the foam.
https://www.loctiteproducts.com/en/products/build/construction-adhesives/loctite_pl_300_vocfoamboardadhesive.html

JUGHNE

My arms ache just looking at your ceiling....I imagine yours might also.

SENWiEco

Thanks @Ironman - I am committed to the products as I already have on site and believe in the quality and performance of the ThermoFin U. I did not get a chance to compare to Sunboard panels but did compare to others, and there was not comparison in quality and fitment to the pex tube. I am just looking for best installation practices for these types of systems.

SENWiEco

@psb75 - Thanks. Yes I have already prepped the drywall contractor that he will need to keep tight control of his team. I will also have the system pressurised so that if they hit a line, we will have water spraying out identifying leak location.

SENWiEco

Thanks @Zman - foam adhesive was going to be my next attempt. My basic questions is how well do these panel assemblies need to be attached. I would imagine that the securing of the drywall would easily carry the minimal load that the panels. tube, and water would represent??

SENWiEco

@JUGHNE - it is not too bad, I have been using https://www.homedepot.ca/product/simpson-strong-tie-quik-drive-pro250-subfloor-system-w-dewalt-2500-rpm-screwdriver-motor/1000787963 to drive the screws

SENWiEco

My overall question: Is there a functional reason that the foam strips and plates need to be rigidly fastened to the OSB or are we only needing to temp support them till the drywall is in place?

psb75

Foam adhesive is really only relevant if it is in actual contact with foam material--not foil face.
Basically you are "tacking" all of the heating material to the ceiling. There IS some value to whatever method you use (glue and screws). The REAL structural "holder" is the sheetrock layer and its multitude of screws. However your questions are totally valid. DO consider the TOTALITY of the "hanging" material--incl. OSB.

psb75

I'm not just "shooting from the hip" here. Anecdote: a general contractor of mine was sleeping one night and he barely escaped (death/injury) when his entire bedroom ceiling fell on him and his wife (sturdy bed headboard!). His ceiling was in a vintage 1960's house that someone had installed some kind of copper-piped hydronic heating system and all of the other (then available) attendant "ceiling-type" materials (incl. "beaver board" and nails). This was 5 years ago and I don't remember all the described-to-me materials and methods--but I do remember when he told me I exclaimed "**** were they thinking?" Oh, he then ALSO took that opportunity to replace all the other rooms that had that same ceiling design. Maybe ins. paid for all of the re-do. I don't know.
KNOW thy materials...and methods. Esp. when operating outside of "norms."

SENWiEco

@psb75 - Many thanks. Good point re foam adhesive. It will never see the foam. I am going to look at https://www.greatstuff.dupont.com/products/greatstuff-pro-construction-adhesive.html or https://www.rona.ca/en/spray-adhesive-751-g-56495022 to see how well it sticks. The OSB has been well secured.

SENWiEco

@psb75 Sounds scary. The copper pipe would have been supper heavy. the transfer plates and pex are lightweight in comparison. Tonight, I will do the math and figure out the load per square foot including the water to get an idea of the load we are talking about.

psb75

Good deal doing your "homework." I agree about the modern lightweight materials you are using--and SCREWS. Contact cement--notsomuch. Don't mean to be hyperbolic and scare you. But these things are...important.

hot_rod

A wide crown stapler works well for foam. I use a 1-1/2 staple for putting the Roth foam panels down, probably fine for overhead work.

SENWiEco

Thanks @hot_rod

Looks like the foam gun adhesive is working really well and is fast. I have finished the panel installation and just starting to run the first loop .

Still generally wanting to know if independent firm attachment of system is needed independently of drywall, or are we just holding everything in place till drywall.

SENWiEco

Thanks all for your suggestions. I switched over to Great Stuff construction adhesive and it is going MUCH faster and it glues up well. I tried to remove a plate I put up by mistake and had a nice cohesive failure where parts of the OSB came off as well.