Bathroom Remodel - Some Basic Insulation Questions for Radiant Floor

smore1945

I'm remodeling a 2nd floor bathroom and I'm interested in adding hydronic radiant floor heating. I've identified a couple different products/methods for this installation but I can't decide which is better for my situation.

The two products I'm considering are uponor quik trak panels, and uponor fast trak panels. I haven't done an in depth cost comparison yet, so at the moment I'm interested in whether one is better than the other for my situation.

My main concern is how I'll properly insulate under the panels. If I use the quik trak plywood panels is it ok to use rigid foam insulation between the sub floor and the panel? If I use the fast trak panel can I do the same? The fast trak 1.3i panel would be ideal with the incorporated insulation but it looks like those have been discontinued.

The existing subfloor is warped and rotted in places so it will be replaced. I could add insulation between the joists. Is that sufficient? I'm thinking any insulation is better than no insulation, but I'm worried the 'correct' r-value in rigid foam might be too thick.

I could ramble on forever but I'll leave it here. I'd love to hear some recommendations for my situation or experiences with either of these products.

Ironman

How many square feet is the bathroom? How old is the house? What’s heating it now? Have you done a Manual J load calculation to determine the actual heat loss?

hot_rod

Floor warming, or trying to actually heat the space? A room with no other heat source?

Is it over a cold crawl space? Why is there no insulation in the joist bays now? The heat load of the room will depend on what is below, a heated or cold space.

The panels with foam work well for over the top. Roth for example, although other brands are available now.

The Roth panel lets you use 6" OC spacing, 3/8" tube for easy installation.

smore1945

Thanks for the responses, I'll try and answer some of your questions.

The bathroom is 50sqft, 28sqft of heated floor. The bathroom is on the 2nd floor of a two story 60 year old house and the space beneath is heated living space. The bathroom is currently heated like the rest of the house with forced air but due to some renovations below I need to remove the duct that supplies the bathroom. I haven't done a full manual J but chatgpt helped me come up with about 900 BTU/hr, but that number presumed adequate insulation in the floor.

The roth panels you mentioned look like they'd do the trick. Unfortunately I can't find anywhere online to buy them, so I'm guessing they're one of those B2B contractor only companies where I'd have to jump through all kinds of hoops with a sales person, so I'm going to stick with the uponor products that are easily available and seem to be competitively priced.

psb75

There is also Warmboard R. This is their renovation board. I believe this has insulation under it. Warmboard S is thicker with subfloor under it. I think the spacing is 12" for 1/2" tubing. Also Sunboard Radiant and Ecowarm.

hot_rod

I get them from LowEnergy in Denver

Also available in NY

Are you going to run this as a separate zone

IMG_9885.jpeg

IMG_9884.jpeg

? What type of boiler do you have?

It will be a tiny zone and could cause an issue for the boiler run time

Mad Dog_2

Forced Air heat? The most economical way to do this is use a small water heater to supply the radiant tubing. Mad Dog

smore1945

Thanks again for all the suggestions and comments. I have tons of little questions about this project but I'll save those for separate posts so the discussion are topical and useful for future readers.

Regardless of the brand, I'm considering 2 different methods/product types. One is a plywood panel with grooves for holding the tube. The second is what I've learned is generally called a "castellated" panel that has nubs that hold the tube and requires concrete or similar to be poured on top. Would any of you experts recommend one method over the other for my situation? And if so how would you insulate?

Kaos

Generally for a remodel project you want to match the tile height to flooring height in the hallway. This means you don't really want anything above the subfloor.

If you don't have a boiler, your best bet is one of the resistance heated mats that go directly under tile. Something like Ditra heat works great, simple install and takes up minimal height.

If you do have a boiler, I would run the heat pipes through the joists. Since you are pulling up the subfloor to replace it, you can run the pipes there and install heat spreaders like UltraFin. When doing this type of heated cavity, make sure to air seal the rim joist area with rigid foam sealed in place with canned foam. Outside air leaks are the enemy of this type of install. You can also insulated bellow the pipes with regular batts.

If you don't have a boiler, you can still do the above install if you use the hot water recirc loop. This only works for small areas which sounds like what you have. The idea is to loop the recirc line under the floor before returning it to the water heater. This should only add a couple of extra feet of pipe. In the winter you can run the recirc all the time to heat the place and on a timer in the summer. The key to this is the water must always be periodically circulated to avoid stagnation.

hot_rod

If you can get under the room, that opens more options.

Any on top system will raise the floor level. Perhaps there is a layer that could be removed if it were an old mud set? There are transition strips to accomodate a small difference in floor levels from room to room.

I would go with electric cable or mat,

or a small 2-1/2 or 6 gallon electric tank if you want pipes instead of wires :)

An example of my go to tank system for master bath floors and walls.

smore1945

I'm set on using hydronics and not electric, I already have the heating source for the water worked out, and I'm set on installing above the joists; I don't have access from below. I've got the details of matching the floor level mostly worked out, but the amount and type and thickness of the insulation is the variable I'm trying to solve for, so that's why I'm asking about the choice between the two different methods.

I can do the math to figure out the R-value needed, but I'm trying to figure out how exactly to go about installing the insulation. I'm guessing I can use rigid foam between the sub floor and the quik trak (plywood type) panel without issue, what about the same with the fast trak (concrete pour type) panels? Do I need a vapor barrier or moisture barrier underneath if I'm pouring the underlayment? What about a decoupling membrane under the thinset and tile?

ILikeEmOlder

From the perspective of a home remodeler:

I think installing insulation above the subfloor in your situation is a non-starter. Trying to accomodate for the extra height of the finished floor is a nightmare scenario is most cases. You are talking about at least an additional 3/4” of height (relative to the connecting hallway and rooms adjacent to the bathroom).

I’ve spent my career as a carpenter (working almost exclusively on older houses), and I can tell you that old houses often present these exact challenges, and the solutions are always a PITA, and always cost a lot of money to execute.

I strongly suggest that you rethink this one.

Kaos

I've installed ultra fins from the top without issues, no need for ceiling access. Pull up the subfloor, drill the joists, put down the batt insulation and air seal rim area, run the pipes, clip on the fins, put subfloor back down. Pretty quick install and since the pipes are well bellow the subfloor you don't have to worry about stray nails.

With old house, make sure the check all your joists and level as needed. For a good tile install especially larger format, the joists should be perfectly flat.

If you really must go for above subfloor, you don't need to insulate. There will be some heat going to the space bellow but since that is part of the conditioned space, the heat isn't lost. The only time this might be an issue is if you have a bedroom bellow the bath in which case you might overheat that bedroom.

smore1945

Kaos- "If you really must go for above subfloor, you don't need to insulate."

It never occurred to me that I don't "need" insulation if the space below is conditioned, which it is. This might be the solution I'm looking for! I totally understand the ability to install the heating to the joists, I just don't like it.

ILikeEmOlder mentioned above the issues I'll have with meeting the existing floor, but without insulation above the subfloor I have no issues. If I replace the current subfloor with the 3/4" ply I already have then i'll have 1.5" to work with. Both the Quik Trak and Fast Trak are 1/2". Tile is 3/8". Need 1/4" for thinset. I have 3/8" left for cement board or build up from the self leveling underlayment.

Am I missing something?

Now, my questions are these:

Do I need a decoupling layer below the tile for either of these applications?

Do I need (or want) a moisture barrier of some sort on top of the subfloor?

Is there any reason to not recess the subfloor flush with the joists and add 3/4" of insulation above the subfloor? Besides the added cost and work involved in recessing the subfloor? In other words if I want to spend the time and money, is it ok to lay that insulation on the subfloor or will that cause a problem I'm not thinking of?

Thanks again for all the help! This is really starting to come together!

epmiller

Maybe I'm missing something here but if you are going to remove the floor down to the joists you can just install fiberglass between the joists and then put the new subfloor down. Lay the quicktrac or whatever on top of that and then the finish floor. That's what I did in my house. I do like some insulation below the radiant heat to reduce the downward losses which will help "push" the heat into the space you want it.

yellowdog

I think 28 sq ft of heated floor will have a hard time heating 400 cu ft of air space.

ILikeEmOlder

Smore,

If you choose not to insulate above the subfloor then you should be fine.

I assume you plan on using 5/16” PEX tubing (laid into the 1/2” Quik Trak panels), is this correct?

To your other questions:

If you choose to use Quik Trak panels, I would consult with the tiling contractor you choose, and allow him\her to work with a system that they are very proficient at installing.

If it were my house (and I was dead-set on radiant tubing), I would install the tubing into Joist Trak panels beneath the subfloor, with 3/4” AdvanTech as the subfloor. Install Schluter decoupling membrane, thinset, then tile. This typically equates to a finished floor height of 1-1/2” (which is almost perfectly level with a typical built up floor height using 3/4” ply and 3/4” hardwood).

smore1945

epmiller "Maybe I'm missing something here but if you are going to remove the floor down to the joists you can just install fiberglass between the joists and then put the new subfloor down."

I agree this way is beginning to look like the easiest way to go about this if I want any insulation at all. I have a weird aversion to fiberglass insulation and I don't have a good reason for it!

yellowdog "I think 28 sq ft of heated floor will have a hard time heating 400 cu ft of air space."

Will it? My rough heat loss calcs are telling me the water heater I'm using shouldn't have any trouble keeping up, but I'll definitely look at it again more closely once i've settled on insulation amounts and their effect on the numbers. Not included in my calcs is the fact that the best place for the pex to exit the heated floorspace is directly under a 1960s cast iron bathtub that probably weighs 300+ lbs., so i'm planning to wrap the pex around it. That'll add quite a bit of heat into the room.

ILikeEmOlder "I assume you plan on using 5/16” PEX tubing (laid into the 1/2” Quik Trak panels), is this correct?"

Yes, I'll be using 5/16 pex as recommended by uponor. I haven't decided between the quik trak and the fast trak, but they both use the same pex. My decision will be mostly based on any difference in cost. They seem to both be acceptable in terms of functionality, unless anyone has an objection to the fast trak with the poured underlayment. If you told me the cost per sqft was identical I would probably choose the fast trak because I have the option to space the pex closer than 7" centers and I like that I'll have a perfectly level surface at the exact height I need after pouring the self leveling underlayment compound.

My tiling contractor is me 😉

DCContrarian

@smore1945 : " I haven't done a full manual J but chatgpt helped me come up with about 900 BTU/hr, but that number presumed adequate insulation in the floor."

@yellowdog: "I think 28 sq ft of heated floor will have a hard time heating 400 cu ft of air space."

The only thing that will determine the heating load is the amount of surface area exposed to the exterior, what that exterior is made of, and the outside temperature. If the floor below is heated, insulation in the floor has no impact on the heating load. The volume of the room really isn't relevant, the room could be exposed on five sides or it could be entirely internal with no outside exposure.

OP said there's an existing forced air heating system. In addition to calculating the heating load, I'd also look at what's there to get a ballpark of what the current heating supply is. I'd also do a fuel-use calculation to sanity-check the heating load calculation.

If the source of the heat is going to be an electric water heater, I agree with the other posters who said just use an electric mat under the tile. It will use exactly the same amount of electricity, and is far easier to install. You don't have to worry about floor height. No pumps, no expansion tank, no running plumbing, no leaks, no purging. No flow calculations. Just turn it on and it works.

ethicalpaul

I have a very small upstairs bathroom and I wanted to heat the floor. I used Quik Trak or however it's spelled, on top of subfloor with tiles on top and it's great. No insulation because I don't care where the heat goes as long as the floor is warm, which it is.

I used water as my heat source instead of electricity just because I wanted to install a hot water loop on my steam boiler, but in your case, unless you're crazy like me, I'd strongly consider the electric kind for its simplicity.

smore1945

https://forum.heatinghelp.com/discussion/comment/1847675#Comment_1847675

what did you put between the quik trak panels and the tile? did you just trowel the thinset onto the panels or did you use cement board first?

I agree with you, and another comment above, that the electric mats are easier and if you're using dedicated water heater then the COP are the same at around 1 (might even lose a bit with the water loop), but my long term goal is a heat pump that will replace my gas furnace, in which case I'll (probably, hopefully) be able to tie the loops into that. Running the water loops on their own on demand electric water heater now is no more efficient than electric, but getting that hot water from a heat pump in the future will be almost free.

epmiller

@yellowdog my one bathroom is a bit over 400 cuft of space, two exterior 2x6 walls (about 40% of the total wall area) with one 9 sqft window. It is the slowest zone in my house but it heats just fine with max water temperature of 125° for the ODReset curve. This was done about 8 or so years ago when all the info I could find said I don't need floor contact with the pex tubes. They were bare tubes suspended in a 2" air space, nothing like UltraFin to help and it worked. Recently I had the ceiling below open so I attached about 1/3 of the tubing that I could reach with sheet aluminum heat spreader plates. Now that area of the tile does get much warmer to the feet and the run time of that zone may be a bit less although it isn't something I care about, as long as my wife is happy. 😄

@smore1945 I have used QuikTrak for a customer and it is a decent system. On that particular job I put down 1/4" Hardie backer and tiled on top of that. I'd be a little reluctant to tile directly on the QuikTrak without something to decouple the tile from all those cracks and gaps. Side note: My son did a bathroom for a customer by covering the floor with aluminum flashing and making the plywood spacers himself for the 5/16" tube. (QuikTrak was out of stock and the Uponor rep told him that's how they did it before QuikTrak.) After helping me with my 1200 sqft QuikTrak job he said he actually prefers the way he did it, it is easier to change spacing of the tubing. (should have read your post more carefully. Definitely wrap the tub, that's what I did on my bathroom remodel, it adds heat output and the tub doesn't suck the heat out of the bath water quite as quickly to boot if the heat is running.)

hot_rod

There are a number of ways to tile over a wood product Ditra is one common product it is the cleavage membrane and waterproofing, but $&

My tile guy still uses a wire reinforcement, thinset, a red liquid waterproofer, then tile over the red sealer

Cement board on the shower walls, seams sealed with the same red

Still others will fasten cement board, seal, then tile. It seems all the tilesetters I have worked around have their preferred method.

TCA Tile Council if America shows the options and approved methods, also

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1847731#Comment_1847731

I had to consult my photos to remember—there was some thermal compound in the channels I think, then thinset I think, then cement board, then thinset for the tiles

hot_rod

https://forum.heatinghelp.com/discussion/comment/1847755#Comment_1847755

the paper roller seems quite distant from the closet flange. Or is it just me.😁

ethicalpaul

haha what’s code? Regardless, this is grandfathered in from decades ago😅

Plus It’s an elongated bowl and those two walls are only like 57” apart

smore1945

hot_rod "There are a number of ways to tile over a wood product Ditra is one common product it is the cleavage membrane and waterproofing, but $&"

I'm definitely aware of the schluter products they've done a good job of marketing themselves, but their stuff is WAY too expensive! I'm sure it works great though and pros probably love working with it. Maybe in the next life!

epmiller "My son did a bathroom for a customer by covering the floor with aluminum flashing and making the plywood spacers himself for the 5/16" tube."

This has definitely crossed my mind. I'd have no trouble at all ripping up a bunch of plywood. The quik trak panels have the aluminum on the bottom, but wouldn't it be better if the aluminum was on top if you could ensure contact? Makes sense to me to draw the heat up towards the tiles and heat the surrounding plywood as little as possible. Or maybe we're splitting hairs in terms of efficiency and it's quicker and easier to install the aluminum on the bottom. I could also use the premade aluminum transfer plates that are widely available. lots of options.

epmiller

@smore1945 Sorry, gone for a bit.

The aluminum just helps spread the heat out. The ratio of the insulating properties of the floor above to the insulation below the heat are key here. I work with a minimum of 1:10, above:below and that seems to work out for me and I use the less expensive stamped sheet aluminum heat spreaders. Getting the heat spreaders in tight contact with the subfloor above is important and then insulate well.

Mark Eatherton

Regardless of your radiant panel decision, the basic rule of thumb is 2 x the R value below the panel as you have above it. 1" foam = R-5, but difficult to work with. Fiber glass is probably your best/easiest option. Use to be able to get R-11, but I think the minimum is now R-15. Not insulating the floor usually causes the space below it to overheat… Your 5th grade techer lied to you. Heat doesn't rise, it flows omni directionally through the path of least resistance.

Kaos

https://forum.heatinghelp.com/discussion/comment/1849031#Comment_1849031

28sqft of heated floor with no insulation at 80F sends 2200BTU to the bath and about 1000BTU to the room bellow. Now that could cause overheat with a small passive house level insulated bedroom but not with a normal house especially if the space bellow is open.

Mark Eatherton

https://forum.heatinghelp.com/discussion/comment/1849038#Comment_1849038

Well, IF (small word, BIG meaning) the room below has enough heat loss, sure it probably may not cause an issue. But I can't tell you how many uninsulated jobs I've been called out to for 2 reasons. 1st reason is space being heated under performs. 2nd reason being the space below it is overheating. Why would you NOT want to put insulation below the panel? Even if the ceiling below is lathe and plaster (worst case scenario) and you didn't make access from above, you can fill the cavity from below with blown cellulose insulation through a 1-1/4" hole/joist bay and 3/4" PEX tube. You have one chance to do it right… Why not take advantage of the opportunity when it's inexpensive and the sub floor may be open. Telling someone that insulation is not necessary is just not right in my book. It IS necessary to guarantee performance and efficient operation.

ME

Mad Dog_2

Oh My Lord...ME in THE HOUSE!!! great to see you visiting us Mark. Mad Dog

TAG

I have done 3/8 tubing over a subfloor with a wet bed and tile with good results … I'm wondering why the OP would not want to insulate under the floor since he has the ability to do it ? You want to insulate.

I think over stuffing the bays with something like rockwool and making a small cut in the rockwool for a tube in the panel would work … this would force the panel against the subfloor when you install it. Maybe even the smallest about of some thin adhesive just in case.

Even 3/8 tubing is going to raise the floor.

Warmboard recommends cement board installed above the panel for tile

psb75

Tile substrate in a bathroom needs to be waterproof before tiling.. Tile and grout are NOT WATERPROOF. You shouldn't adhere tile to a surface that will get regularly "wetted" unless it has been completely waterproofed before applying thinset and tile. All to say, you should be able to use the shower before it has been tiled.