Radiant heat install, above floor

[tltaylor22]

So my kitchen project is moving along. One of the things I am doing is installing pex over the floor boards and then new tile. I've talked to several people about how to do this and get a different answer each time. Here's the scenerio. I've already got the boiler and run forced hot water to some base board heater units. The area that I'm looking to add heat to is 650 sq feet. I had a heat loss calc done and was told to run 3 x 250' lines with 8"spacing between the 1/2" pex.

The original floor has 1" pine planks on the diag. with 3/4" plywood over the top of it. It then had a 1/2" article board stapled to that with Saltio tile over the top. The tile and 1/2" board are being removed. I looked at having the pex poured into a cement slab over the floor, but expense and engineering prohibit it. What I propose is ripping a bunch of 1/2" plywood into 8" strips and laying it spaced out to make the groves for the pex. I'll router half round end caps for the pex bends. Should I staple the pex down into these grooves?

I was then going to scratch coat in a layer of Hardy backer and then my 20" tiles. Should I leave any sort of expansion joints for the heat and cool cycles? What am I missing or misthinking on this? The basement cieling under this floor could be insulated is needed. Do I need an additional pump or can I run a line of the discharge of the existing system? My boiler is way under used right now as I ripped out 3/4 of the baseboard heat that was in the house when I bought it. I hated having my furniture a foot away from all the walls.

 

[Joe_E]

I don't have an answer for you but I should of done this in our master bath. I was talked into a single toe kick heater under the vanity which absolutely is terrible in mid winter.

All the hot water radiant heat I have seen on the home shows on tv have them using a flexible pipe weaved back and forth. If I remember they poured a thinset mix over the whole pipe system and troweled it off. Tile was then laid on top.

 

[EricG]

Under floor radiant typically runs at a significantly lower temperature then baseboards. I think you'll need a separate circuit & thermostat at a minimum.

 

[tltaylor22]

Good point Eric. I'll look into what i have the boiler set at for the baseboard. I have no problem adding a second pump and all that. How do thermostats fro floor heat work? Is there something I embed in the mortor?

 

[EricG]

Good point Eric. I'll look into what i have the boiler set at for the baseboard. I have no problem adding a second pump and all that. How do thermostats fro floor heat work? Is there something I embed in the mortor?

No, just a regular wall mounted thermostat - the point is keeping the air temp where you want it.

 

[FJ40_owner]

You could easily add a floor sensor in the grout. They are smaller than a cigarrette.

Using a room sensor you will have alot of lag.

Once you understand how your load works the floor sensor will allow more precise control.
Are you using a controller that has adjustable parameters or a dumb thermostat?

 

[haystax]

Couple of ?? What type of floor joist? Exactly what type of finished tile? How hot is your boiler output currently? Is it cast iron? What brand of PEX are you planning to use? You will need oxygen barrier tubing and the pex-al-pex stuff is much nicer to work with because it keeps its shape. It would be a little work but you will probably be fine with the router and sleeper method. I would also suggest looking into a product called Ditra from Schluter systems that I used rather than hardibacker. You can save some height that I ultimately needed for the dishwasher to fit and the floor transition is much nicer w/o the hardi

The absolute best forum for your questions is heatinghelp.com and then click on "The Wall"

I think you will need a tempering valve to lower the floor temp and probably and additional circ pump and t-stat for that room. I did not use any slab or floor sensors and have found that the system responds just fine, maybe there is a benefit but I cannot tell. I have been very happy with Uponor products. There are dual sensor t-stats that use a combination of floor and air sensors and Tekmar makes Uponor's electronics and are pulse modulating to better control radiant heat systems. A single t-stat running a pump relay to a Grundfos 15-58 circ should handle your needs easily.

You may run into problems of returning too cold of water to the cast iron boiler and risk temp shocking the unit. You may also be able to use an injection type mixing system rather than a dedicated circ pump. Grunfos has some excellent literature and Wilo makes a very cool ECM circ pump but you should be able to get by with a very simple dedicated pump.

Good luck - here's a shot of my system that i installed, it's pretty easy once you decide to jump in and get to work.

 

[tltaylor22]

Haystack,
Great questions. This part of the house was built in the 1950's so I have solid pine 2x10 for floor joists. The finish tile is porcelain 20". I'll look up the boiler info when I get home. I have not bought the Pex yet, but had planned on an oxygen barrier hose.

I've had several people recomend the Ditra material and several people say not to use it. Comments have been split down the middle. I really just want to use whatever it takes to make sure that the tile doesn't crack. I'm only doing this kitchen once and I'm living in this house for a while.

 

[haystax]

Google the term - "deflectometer" and see what it says about your floor joists and the deflection recs for porcelain. We have marble over 11 7/8" TJI joist on a 13' span plus the 1 1/8" Warmboard. I wasn't sure about the Ditra but after reading several forums I decided it was the safest bet.

I think John Bridge has the best info and forum for this type of thing.

Where are you located?

 

[tltaylor22]

Finally home from work. I'm in Utah and went and visited Standard Plumbing's Hydronic Heating supply today. I think I have a good list of parts going now for my system. I will need a mixer to drop the temp on the floor loops to 120f. The guy I was working with said that was pretty normal. I believe my boiler is Cast Iron. It's a 50k BTU Peerless. I've got a 150k BTU boiler in the garage, but I'm pretty sure I'm alright with the one I have installed already. He wasn't to worried about the cold water issue as long as I had the mixing valve and new pump hooked up right.

Your 1 1/8" Warmboard, was that installed right on top of the Joists? I've got the original 3/4" pine flooring plus a layer of 3/4" plywood over that. Turns out my joists aren't 10" they're the standard 2x8's. The spacing is a little wierd. Some are 16", some are 14". Then there are doubles about every 6th joist. When I ran the Deflecto (Great link btw, John Bridge forum has lots of info.) it said I was good for ceramic, but not Stone. I read a few places in the John Bridge forum that if it passes for Ceramic it will be fine for Porclain. Does that sound right?

BTW Haystack,
Your system is way to clean looking. I'm thinking more like a spahgetti bowl...Actually it gives me something to am for.




I will tell you that out of all the forums with different topics, IH8MUD and Expedition portal are the best. Yeah we get some differences of opinion here, but on the tile forums things seem to go accross the board. Everyone has a different answer on how to do stuff.

 

[Toyo FJ40]

I've done the type of install your thinking about, sandwiched between 2 layers of plywood. If your putting tile over it I would just put wire lath over tar paper and wire tie the pex to the wire and put a wet bed over the pex. It's easier than sandwiching the pex and gives better heat transfer. Plus no chance of hitting the pex when nailing down the hardybacker.
Don't forget that radiant doesn't work as well if you don't insulate under it.
You can do slab sensor or wall thermostat. I have never had a problem with wall thermostats as long as you don't change the temp. Set backs don't work unless you give it 3 to 4 hours lead time to come up to temp. If you do a slab sensor I would use an outdoor reset so the slab will stop heating when it hits say 68 degrees outside.
Taco makes a radiant block that has a zone pump and a injection pump with outdoor reset to vary the slab temp by outdoor temp all in one unit. Taco Mixing Block

Kevin

 

[tltaylor22]

Kevin,
By wet bed do you mean pouring the whole floor with like an 1" or more mortar? I had someone bid to do a light weight concrete pour 1 1/2" thick, but it was a crazy amount of money. I'm using 1/2" pex. Could I get away with 3/4" or less of mortar, just enough to cover the tubing. Then just lay tile over it? How much Wieght would the wet bed add to the floor? Just worried about the floor joist with that much wieght. This part of the house was built in the 1950's.

I like the Taco Mixing block. Looks slick. I'll see if I can source one local.

I spent some time with a local commercial supplier who recomended the Ditra instead of CBU. I have had professionals tell me that I would be fine with putting in my sleepers and tubing and then laying CBU right over the top. Others have said I need to lay a 1/2" layer of plywood over the tubing and then CBU. Others have said to avoid the CBU all together and use the Ditra ove rthe extra plywood. As long as it doesn't break the bank or crack the tile, I'm good with what ever. The wife would kill me if I crack her new 20" porcelain tile.

 

[Toyo FJ40]

Wet bed is a sand mix concrete, not morter, that is mixed with very little water like a morter mix you would use to set stone. It is leveled and packed over wire lath and tiled over with a thin set. If your subfloor is solid you can do a 3/4" wet bed but over pex but a 1 1/4" would be better. I just finished a job were they just filled in between the pex with wet bed and then layed 2" thick limestone slabs over it. But it was over an insulated concrete slab so it well supported.
How big an area are you working with?
Wet bed


Kevin

 

[tltaylor22]

I've got 650 sqft. Wet bed soudns interesting. The link said 4 or 5 to 1 sand /portland. That is basically what I used to do the 1000 ft of lawn curbing in the yard.

 

[haystax]

You need to be sure that your floor framing can support the added weight of the mortar -

1 1/4" makes for a tall transistion to other floors and will definitely alter you cabinet and countertop heights, might not be room for a dishwasher to slide under a countertop.

Just a couple observations -

 

[Toyo FJ40]

It's pretty simple. You can lay boards down that are the thickness that you want and then fill between them and level with a straight edge. Then pull the boards and fill the gaps in. 20" tiles will need a real flat surface so that you don't have corners that don't line up. You'll just have to check that your level both ways as you lay the wet bed.


Kevin

 

[Toyo FJ40]

Now concrete weighs about 4000 lbs per Cubic Yard dry and if my maths right you need about 2.5 yards to do 1.25" so the weight should be around 10000 for your floor or about 15 1/3lbs per sq ft.

 

[tltaylor22]

I'm making slow progress on the radiant. My father and I installed all the sleepers during the last week and last night ran the three 250' loops. It actually looks really good. I will hook all the loops up tot the manifolds thrusday night and then we'll start laying the 4x8 sheets of 1/2" CBU.

 

[tltaylor22]

This remodel is killing me. We laid 100 sqft of the 20" porcelain tile when I broke one while bedding it down. After inspecting the break I found a hairline crack that was in the tile before the glaze was fired. I then went through all the ones i had laid and found a few more. After replacing those I went through several boxes in my truck and had a 10-15% failure. I spent the morning with the importer of the tile and they are dropping off all new stuff in the morning. Being in the business I'm in I understand how frustrating it can be to bring something in and have problems that are not your fault. I'm not mad at the company I bought it from or the importer for that matter. I did insist that the importer go back to her boss and the manufacturer and figure out what it's worth to them to make it right beyond the replacement tile. I lost 2 day of vacation time, my father took two days off of work and my grandfather who is a General Contractor drove 200 miles to come lend a hand for a few days. They are lucky I found the problem now instead of when I turned on the heat and started snapping tiles. Then I would have them on the hook for removal and reinstallation for faulty product. Because of my work schedule I now have to hire someone to come lay the tile, in order for me to have this thing wrapped up before thanksgiving. We'll see what they do I guess.