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DIY pex underfloor radiant heat

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Elbryn said:
i thought about placing heating elements under the tile in the bathroom when we remodeled it. know what we ended up doing? rug in front of the sink and a portable heater that plugs in. it'll take a good while for you to heat through subfloor, thinset, and tile before you actually felt heat, unless you left it on all the time. it's far easier and efficient to turn a portable space heater on on the floor when you get in.
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I did something similar. But I put in a ceiling fan that had a heater built in. The fan cost about $50 and there was roughly $25 for electric wire, another circuit breaker, and a new switch. $75 for heat right where you need it. Safe, reliable, instant heat. A $10 portable heater like you mention would work just as well, but I liked the built-in idea on a separate circuit so that a hairdrier wouldn't overload anything.
 
If you really want to do this, call a reputable contractor (read: not the cheapest guy in the yellow pages) and get a quote on this. Take this number and multiply it by 2.5 to find out much it'll cost after you try and do it yourself, fail, and have to get the contractor in to fix what you did and then do the job correctly.
 
So much hate for the DIYer in this thread. While there is a reason that professionals make the money they do, pex is quite easy to work with. the learning curve is small. Fittings, tubes, crimp tool rings and a proper layout and you should be good to go. You might want to consult someone about your heat source, but the recirc pump and the zone valves are simple enough to install. Pex is damn foolproof in the install. Some large retails who sell pex also offer free designs and parts lists. They want you to do it right and by giving you the proper layout and parts they make the sales.
 
Physically making the connections is the easy part. I think you are underestimating all the labor and knowledge that goes into this type of installation. There are volumes and volumes written on hydronics. Not to mention that they type of boiler that excels in these installations require expensive tools to properly calibrate.
 
Greenman said:
Radiant heat using electrically heated water is going to cost a fortune to run. Also, if your going to do this in a wood subfloor keep in mind that rats chew through pex. They do it enough that the material is banned in the county where I live.
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They do it enough? I've never heard of rats chewing through Pex. They can - but I've never heard of it. I have 1000 feet of Pex in my barn. I've had 2 major rat infestations. Lots of chewed wood. Not one bit of the Pex has been touched.
 
waffleironhead said:
So much hate for the DIYer in this thread. While there is a reason that professionals make the money they do, pex is quite easy to work with. the learning curve is small. Fittings, tubes, crimp tool rings and a proper layout and you should be good to go. You might want to consult someone about your heat source, but the recirc pump and the zone valves are simple enough to install. Pex is damn foolproof in the install. Some large retails who sell pex also offer free designs and parts lists. They want you to do it right and by giving you the proper layout and parts they make the sales.
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THIS is probably a bigger reason why Pex is banned in certain areas - strong plumbers union convinces local zoning boards that rats chew through Pex. (Rats chew through electrical wires too but NM-B is still allowed by code - because most DIYers are frightened of doing their own wiring.) Sweating copper joints - more fear from casual DIYers about leaks. Toss in some damn near impossible to screw up Pex...
 
GregGreen said:
Physically making the connections is the easy part. I think you are underestimating all the labor and knowledge that goes into this type of installation. There are volumes and volumes written on hydronics. Not to mention that they type of boiler that excels in these installations require expensive tools to properly calibrate.
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Hence why I asked, I'm was hoping for actual tips, instead of bashing. Questions that come to my mind are things such as, if I need a manifold, sizing, and after NN feet how much heat is lost, what is best type of pump, or best way to heat the water etc lot of things to consider... I'm willing to experiment. There is a great sense of accomplishment when something made nearly from scratch is up and running. I also want it to be safe, some of the ideas that crossed my mind were quickly discarded, such as making a coil out of copper, putting it in front of an electric heater and shoving the whole thing in an insulated box. That's probably a fire waiting to happen if the thermostat is not set correctly, or fails.

The best thing I've thought of so far is to use the smallest electric water heater I can possibly find. Not sure how well those work under low pressure situations though. Guess as long as the water level is above the element at all times.
 
DrPizza said:
They do it enough? I've never heard of rats chewing through Pex. They can - but I've never heard of it. I have 1000 feet of Pex in my barn. I've had 2 major rat infestations. Lots of chewed wood. Not one bit of the Pex has been touched.
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I should have elaborated on that a bit more. The problem they were having around here is with rats that were poisoned with common rat bait. Apparently the poison kills the rats by making them bleed out internally, that makes them very thirsty before they die. The theory is that they can smell water through the pex, and chew through it to get at the water they need. I have no first hand knowledge of this, it's the official story from the local building department. Pex was allowed here for several years, until the rat damage became common enough that they declared the material as unsuitable for use in the county. I've herd of several other city's here in CA that are having similar issues with it.
 
RedSquirrel said:
Hence why I asked, I'm was hoping for actual tips, instead of bashing. Questions that come to my mind are things such as, if I need a manifold, sizing, and after NN feet how much heat is lost, what is best type of pump, or best way to heat the water etc lot of things to consider... I'm willing to experiment. There is a great sense of accomplishment when something made nearly from scratch is up and running. I also want it to be safe, some of the ideas that crossed my mind were quickly discarded, such as making a coil out of copper, putting it in front of an electric heater and shoving the whole thing in an insulated box. That's probably a fire waiting to happen if the thermostat is not set correctly, or fails.

The best thing I've thought of so far is to use the smallest electric water heater I can possibly find. Not sure how well those work under low pressure situations though. Guess as long as the water level is above the element at all times.
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Sorry if I came across as condescending. It is often more of a project than it can seem. I would still recommend contacting some contractors. Find one that will design the system or get the system designed for you on the condition of you installing it yourself. A lot of people don't understand that there is a lot more to it than hooking pipes to a water heater and praying. Unforunately, I know enough to know that but not enough to actually help you design the system.

And if you do it all yourself, DO NOT forget to install oxygen barrier HePEX -- otherwise you will rot out your heat exchanger.
 
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That's really weird then - none of my lines are copper; we completely re-did everything around the farm with Pex. I've poisoned dozens upon dozens of rats. Zero problems with the Pex. I'm sure there are probably a few anecdotal stories out there, but I've never heard any reports of problems in my area, especially from people I trust. While googling around, I did run into a picture of one piece of pex that was chewed through by rats looking for water. Must have been at least a dozen holes all the way through; all I could think is "yeah, right." After one hole, I think a rat would have all the water it wanted.
 
DrPizza said:
That's really weird then - none of my lines are copper; we completely re-did everything around the farm with Pex. I've poisoned dozens upon dozens of rats. Zero problems with the Pex. I'm sure there are probably a few anecdotal stories out there, but I've never heard any reports of problems in my area, especially from people I trust. While googling around, I did run into a picture of one piece of pex that was chewed through by rats looking for water. Must have been at least a dozen holes all the way through; all I could think is "yeah, right." After one hole, I think a rat would have all the water it wanted.
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I work at a plumbing supply house atm and I have never heard of anything like rats chewing through PEX lines. I'll see if I can find out more at work tomorrow.
 
DrPizza said:
That's really weird then - none of my lines are copper; we completely re-did everything around the farm with Pex. I've poisoned dozens upon dozens of rats. Zero problems with the Pex. I'm sure there are probably a few anecdotal stories out there, but I've never heard any reports of problems in my area, especially from people I trust. While googling around, I did run into a picture of one piece of pex that was chewed through by rats looking for water. Must have been at least a dozen holes all the way through; all I could think is "yeah, right." After one hole, I think a rat would have all the water it wanted.
Click to expand...

I've never investigated the issue. I used pex in a house I built and liked it, then decided to use pex exclusively, and within 6 months it was banned. I'm just going to go ahead and assume the whole thing wasn't my fault.
 
RedSquirrel,

You should stop thinking out loud

It is a simple concept but much more difficult to apply than you think. There are many large projects that fails even with mechanical engineers and master plumbers working on it.

<---- plumber, gas fitter, HVAC mech, heating cooling/geothermal specialist
 
Greenman said:
I've never investigated the issue. I used pex in a house I built and liked it, then decided to use pex exclusively, and within 6 months it was banned. I'm just going to go ahead and assume the whole thing wasn't my fault.
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Where is the ban?

It is use exclusively in residential in Canada, and I think most if not all of US residential construction as well., Commercial/industrial must use copper.
 
Hot water radiant heat under a floor is only worthwhile if you already have a boiler (like if your house is already set up with radiators). It could make sense if you are doing a full-on renovation and have most of the house torn apart...and are planning to make it your primary heat source. To try to retrofit a single room with hot water, though, is simply stupid.

If you want radiant heat in a small area or a single room, an all-electric system is a simple (and DIY-friendly) way to go. My wife and I installed one in our entryway under granite tile. It was easy...put down the backer board, staple the mat and make sure the leads are out of the way, lay the tiles, and then wire everything up. It's not as efficient as a hot water system, but it's much better than installing a boiler for a single 5' x 13' area.
 
waffleironhead said:
I was under the impression that barrier pex was only required with ferrous parts, or is that what you were referring to.
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Oxybarrier is a good idea for heating, however you can use a pot feeder or injector to mix inhibitor to protect metals (copper/brass/iron).
 
reitz said:
Hot water radiant heat under a floor is only worthwhile if you already have a boiler (like if your house is already set up with radiators). It could make sense if you are doing a full-on renovation and have most of the house torn apart...and are planning to make it your primary heat source. To try to retrofit a single room with hot water, though, is simply stupid.

If you want radiant heat in a small area or a single room, an all-electric system is a simple (and DIY-friendly) way to go. My wife and I installed one in our entryway under granite tile. It was easy...put down the backer board, staple the mat and make sure the leads are out of the way, lay the tiles, and then wire everything up. It's not as efficient as a hot water system, but it's much better than installing a boiler for a single 5' x 13' area.
Click to expand...
Efficiency is not the only thing, electric mat/wire heating isn't the same as hot water because the heat intensity is higher (no mass heating) therefore it is easier to have hot/cold spot and certain time it is hot & other time it is cold.

Infloor water piping heated water generally run between 90-130F, and default is 110-120F, therefore it is less likely to have hot spot if it was design well (supply line out at the perimeter & return in the middle).
 
RedSquirrel said:
Hence why I asked, I'm was hoping for actual tips, instead of bashing. Questions that come to my mind are things such as, if I need a manifold, sizing, and after NN feet how much heat is lost, what is best type of pump, or best way to heat the water etc lot of things to consider... I'm willing to experiment. There is a great sense of accomplishment when something made nearly from scratch is up and running. I also want it to be safe, some of the ideas that crossed my mind were quickly discarded, such as making a coil out of copper, putting it in front of an electric heater and shoving the whole thing in an insulated box. That's probably a fire waiting to happen if the thermostat is not set correctly, or fails.

The best thing I've thought of so far is to use the smallest electric water heater I can possibly find. Not sure how well those work under low pressure situations though. Guess as long as the water level is above the element at all times.
Click to expand...
Yes you will need manifold. Depends on the run, temperature lost/volume/seasonal temperature average/windows/doors, the size & length of run can be any where 0-450f using 1/2"-5/8" tubing. Each zone can have individual manifold or combination of zones to 1 manifold with each loop manually or electronically control by mixing valves/thermostats/pressure valves/actuators. Then there are a gamut of stuffs in the mechanical room including safety, fail safe, and backup systems.
 
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