DIY pex underfloor radiant heat

Red Squirrel

No Lifer
May 24, 2003
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Has anyone tried this? I have a couple ideas for a cheap DIY floor heating solution, but curious if anyone has ever tried to do it themselves.

Basically you have a water reservoir and a pump that pumps it into tubes then it returns back. Somewhere along the lines it is heated, the heat generated by the pipes eventually radiates through the floor, heating the floor above.

There are systems you can buy that do it for you, but it seems like it would be easy to DIY. Just not sure yet how I'd heat the water safely yet. A very small electric hot water heater is probably the best bet.
 

xanis

Lifer
Sep 11, 2005
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Why would you want to do this? Just wear socks and/or slippers. Problem solved. :p
 

Eli

Super Moderator | Elite Member
Oct 9, 1999
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Has anyone tried this? I have a couple ideas for a cheap DIY floor heating solution, but curious if anyone has ever tried to do it themselves.

Basically you have a water reservoir and a pump that pumps it into tubes then it returns back. Somewhere along the lines it is heated, the heat generated by the pipes eventually radiates through the floor, heating the floor above.

There are systems you can buy that do it for you, but it seems like it would be easy to DIY. Just not sure yet how I'd heat the water safely yet. A very small electric hot water heater is probably the best bet.

LOL

I will reiterate - LOL.

Unless you are a master plumber, this is a nightmare waiting to happen.

You are an inquisitive individual, but it seems you tend to way underestimate the complexities of things.

It would be MUCH easier to just get the bare heating elements and then have cement or whatever is used poured over them. Having water plumbed through your floor in a grid for heating is a horrible, horrible idea - for a DIY project.
 

Red Squirrel

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It's been done, just wondering if anyone has it and how well it works.

http://www.radiantec.com/installation-manual/do_it_yourself.php
http://www.aimradiantheating.com/store/underfloor.html
http://www.houseneeds.com/Shop/Heatingproducts/heatu/underfloorhowto.asp

The heating pads added with the tiles is another solution but it's kinda hard to do when the tiles are already in place. :p

Apparently some people actually use this as their main source of heat, but THAT I have a hard time believing, unless they live in California and think that +25 is cold. It's more or less a secondary heat.

Not sure how long it takes for it to actually get through the various thicknesses of floor though.
 
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DrPizza

Administrator Elite Member Goat Whisperer
Mar 5, 2001
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It's not that complicated of a project - if you know exactly what you're doing. As far as worrying about leaks - that's the last thing in the world I'd worry about if I was running Pex.

However, if you're going to use electric to heat the water, why not just put in electric radiant heat under the floor? Why add in a middle step?
 

Greenman

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Oct 15, 1999
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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.
 

Red Squirrel

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lol if I had rats under my floor that would be a problem on it's own. I'd be more worried about them chewing through electrical and data lines and would have dealt with it a long time ago, or would of not bought the house.

I calculated and it would cost me about 30 bucks a month extra to run this if I go with 3kw, which is oversizing. The source of heat would probably not have to stay on the whole time. Not yet sure how I'd heat it. I thought of a few ways but the safest seems to be a small hot water heater.

I thought of getting heated tiles but at the time the tiles were installed I just never figured I'd need it and was way over budget to begin with. And yeah pex sounds pretty easy to work with so leaks are not really a concern.
 

Jeff7

Lifer
Jan 4, 2001
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It's not that complicated of a project - if you know exactly what you're doing. As far as worrying about leaks - that's the last thing in the world I'd worry about if I was running Pex.

However, if you're going to use electric to heat the water, why not just put in electric radiant heat under the floor? Why add in a middle step?
Additional benefit: Instead of waiting for the heaters to warm the water, which will then warm the floor, using the heating elements to heat the floor directly will get the job done much quicker - unless you keep the water heated all the time, which I suppose could work too, assuming you've got an insulated tank available for the job.


A cheap solution: Throw rugs. :D
 

Red Squirrel

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Additional benefit: Instead of waiting for the heaters to warm the water, which will then warm the floor, using the heating elements to heat the floor directly will get the job done much quicker - unless you keep the water heated all the time, which I suppose could work too, assuming you've got an insulated tank available for the job.


A cheap solution: Throw rugs. :D

Actually those tile pads can take a good 12 hours to heat up. My parents have heated tiles in the washroom downstairs where I used to always get ready in the morning when I lived there. If the switch was off and turned back on heat would not be felt till next day. They are pretty much meant to be kept on and don't think they use much power, so yeah that would have been the best solution but can only be done before the tiles are installed.

One thing to consider with my system is transfer plates too, just the pex alone will take a while to go through the floor, transfer plates may help a bit. Heat rises though so I can use that to my advantage. Not sure how long it would take to really feel the heat, and how long it would take for it to go away when turned off. I'm thinking a couple hours at least. I've thought of using solar heat but I doubt that would make any difference.
 

Red Squirrel

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Did not start on that yet but I've been playing with different designs. I'm thinking of incorporating a 4 post rack into the equation, those can be had for 500 bucks which is somewhat reasonable. That way I could get true U size (my design wastes lot of space) and be able to easily setup standard rack mount equipment. When I do my rec room I'll try to get all my sound stuff rack mountable too.

That's probably going to be a project for once my loan and furniture is paid off. Same with this heating system. Looking at prices of pumps and various HW heaters, it wont come cheap. I probably wont even end up doing it, just an idea at this point. I got the idea when I realized how hot the floor gets where the furnace ducts pass by and upon some further research turns out some people do it professionally.
 

Eli

Super Moderator | Elite Member
Oct 9, 1999
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It's been done, just wondering if anyone has it and how well it works.

http://www.radiantec.com/installation-manual/do_it_yourself.php

The heating pads added with the tiles is another solution but it's kinda hard to do when the tiles are already in place. :p

Apparently some people actually use this as their main source of heat, but THAT I have a hard time believing, unless they live in California and think that +25 is cold. It's more or less a secondary heat.

My fiancee and I house sit for some folks that have radiant heat as their main source of heat. It's actually really nice. The only downside is the lag - it takes 2-4 hours to raise the temperature appreciably. But once it's warm, it is a nice heat.

Anyway.. Well, OK.. maybe I was a little harsh. I was thinking like, DIY all the way .. from finding fittings, etc. If you just took one of the current systems and installed it yourself, that probably wouldn't be so bad.
 

skyking

Lifer
Nov 21, 2001
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It is a common method for heating slab-on-grade homes. It also lends itself to solar heating systems, and you can supplement the solar with an inline boiler as needed.
I'm kicking around a design for a slab-on-grade beach house for our lot.
http://www.dawnsolar.com/gallery.html
Check out the pex tubing collection systems in the lower pictures, the combined solar/PV systems too.
 

Greenman

Lifer
Oct 15, 1999
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lol if I had rats under my floor that would be a problem on it's own. I'd be more worried about them chewing through electrical and data lines and would have dealt with it a long time ago, or would of not bought the house.

I calculated and it would cost me about 30 bucks a month extra to run this if I go with 3kw, which is oversizing. The source of heat would probably not have to stay on the whole time. Not yet sure how I'd heat it. I thought of a few ways but the safest seems to be a small hot water heater.

I thought of getting heated tiles but at the time the tiles were installed I just never figured I'd need it and was way over budget to begin with. And yeah pex sounds pretty easy to work with so leaks are not really a concern.

If your house has never had a rat in it, that would make it the first one I've come across in thirty years of remodeling.
 

krylon

Diamond Member
Nov 17, 2001
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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.

Lurkers coming out of the woodwork to talk about rats. This thread gains my seal of approval.
 

geno

Lifer
Dec 26, 1999
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RSO105-crew-socks-lg.jpg
 

drnickriviera

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Jan 30, 2001
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lol if I had rats under my floor that would be a problem on it's own. I'd be more worried about them chewing through electrical and data lines and would have dealt with it a long time ago, or would of not bought the house.

I calculated and it would cost me about 30 bucks a month extra to run this if I go with 3kw, which is oversizing. The source of heat would probably not have to stay on the whole time. Not yet sure how I'd heat it. I thought of a few ways but the safest seems to be a small hot water heater.

I thought of getting heated tiles but at the time the tiles were installed I just never figured I'd need it and was way over budget to begin with. And yeah pex sounds pretty easy to work with so leaks are not really a concern.

You sure about that sizing? That only works out to around 10,000 BTU.
 

Red Squirrel

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May 24, 2003
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If your house has never had a rat in it, that would make it the first one I've come across in thirty years of remodeling.

Not really, if it's properly sealed off from the outside there's no reason for any rodents to get in. It happens that people have rodent issues but if dealt with it should not become an ongoing issue. This house was built in 1965 and I see zero signs of rodent issues. No chewed wires or anything.
 

Elbryn

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Sep 30, 2000
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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.
 

Red Squirrel

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May 24, 2003
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You sure about that sizing? That only works out to around 10,000 BTU.

Yeah it's not for the whole house just for a small section, about 200 square feet or so. I'd almost have to do a small scale model to test as I have a feeling there are too many floor thicknesses for it to go through.

I should have just got the one that go right under the tile before the tile was put in. Easier and lower wattage. :p