Running Hot Water Under Subfloor to Heat Kitchen Tile

Reply

  #1  
Old 01-28-10, 08:26 PM
Member
Thread Starter
Join Date: May 2007
Location: New Jersey
Posts: 193
Received 0 Votes on 0 Posts
Running Hot Water Under Subfloor to Heat Kitchen Tile

Hey there. The tile floor in our kitchen is pretty cold in winter. We have an unfinished room below the kitchen in the basement room (the rest of the basement is finished).

The ceiling in that basement room has some very old fiberglass insulation in about 1/4 of the joists. It's very thin insulation and the kraft facing downwards is brittle And flaking.

We may eventually finish that room someday (as an office), but for now we'd like to try and get our bare feet a bit warmer on the floor above. I prob should have installed heat in the floor before I put it down myself, but alas, I didn't.

The house is heated in a single zone (ranch style home) with hot water radiators. There is a radiator pipe for the kitchen running through the room below.

I read that I can run Hot lines along the joists to heat the kitchen floor above. Obviously putting in some new insulation to hold that heat in and send it upwards.

A few questions:

-Is this effective. and if so...
-Would I have to run lines it through every joist? or would every other do?
-Could I use PEX or is Copper more conductive?
-Would it be as simple as tapping into the hot water line and creating a loop of some sort?

Just trying to weigh my options. Any help is appreciated.

Thanks

Fish
 
Sponsored Links
  #2  
Old 01-28-10, 08:57 PM
Member
Join Date: Jul 2009
Location: Toronto
Posts: 1,174
Received 0 Votes on 0 Posts
Give this a read,
http://www.wattsradiant.com/literatu...N-20050501.pdf

Onix is so easy to install and works very well.
Use it all the time.

Not the cheapest pipe around, but it's ease of installation makes up for the price.
 
  #3  
Old 01-28-10, 09:03 PM
Member
Thread Starter
Join Date: May 2007
Location: New Jersey
Posts: 193
Received 0 Votes on 0 Posts
Originally Posted by TOHeating View Post
Give this a read,
http://www.wattsradiant.com/literatu...N-20050501.pdf

Onix is so easy to install and works very well.
Use it all the time.

Not the cheapest pipe around, but it's ease of installation makes up for the price.
Thanks! Just took a quick look. Looks very interesting. Gotta look at it in more detail tomorrow.

Thanks for the suggestion!
 
  #4  
Old 01-28-10, 10:50 PM
Member
Join Date: Jan 2009
Location: Northwestern Ontario (Canada)
Posts: 549
Received 1 Vote on 1 Post
You wont regret adding some in-floor (underfloor) for your tile kitchen.. ceramic is just too dang cold on its own to be comfortable. Depending on the heat loss of that kitchen (roofing/second story, walls, windows, adjoining rooms) , the heat btu requirements might not make the floor 'warm' (as in, wanna lay down and nap on it).. but it will certainly rise way above the 'sucking the cold out thru your feet' feeling.

Too many sales sites imply that in-floor makes for 'warm floors'.. but you'd have to have a serious amount of heat loss to maintain a 'warm' tile floor.

I guess they cant really market a 'uncold' floor though.. lol

Matter of perspective..
 
  #5  
Old 01-29-10, 07:32 AM
rbeck's Avatar
Member
Join Date: Jul 2007
Location: Pennsylvania
Posts: 2,456
Received 2 Votes on 2 Posts
Fishy there are two types of radiant applications. Radiant heat or floor warming. What's the difference you ask....water temperature. For floor warming you are not counting on the radiant to be the sole heat source of the kitchen but just warm up the floor. This is doable and can work on lower water temperatures plus adds to the heat of the room.
You will need a mixing valve, pipe, fittings, circulator and tubing to name a few items. Usually you make 2 passes in each joist. Insulation must be at least an R-19 and leave 2" below the tubing unless you use the aluminum plates than the insulation can be right up against the plates.
To control this you have two options;
1. run the pipes back to the boiler and start the boiler as needed.
2. Run continuous pump with an on/off switch. The common zone will run enough to accomplish floor warming just teeing into the common heating pipe. There will be nothing to start or stop the boiler from the radiant zone. I did my kitchen this way in another house I lived in and it was the primary heat for the kitchen and worked fine.
Just dial in the temperature you want need, trial and error and turn it on in the fall and off in the spring. The lowest temp you can use and maintain the warm floor the better.
 
  #6  
Old 01-29-10, 07:45 AM
Member
Thread Starter
Join Date: May 2007
Location: New Jersey
Posts: 193
Received 0 Votes on 0 Posts
Thanks for the replies guys... I guess I was hoping to just tap into the existing radiator pipe that feeds the kitchen. That pipe from the boiler is already below the kitchen so I thought it would be easy. So since its single zone, whenever the heat it the house is on the floor would get some heat. Seems like the easiest way. But maybe not idea since the floor wouldn't get heat as often as I might like. I was wondering if that would affect the heat in the rest of the house. Is that possible?

rheck, what tubing type do you recommend? Is one better than another? I had hoped Pex would work since its flexible and easier to work with but probaby not a good conductor.

To be honest I'm wondering if this is all a bit over my head. I think I'm capable of doing it I just wonder if I have the time or patience

Thanks again

Dave
 
  #7  
Old 01-29-10, 06:15 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Dave, PEX is used in heating systems all the time, but the stuff that's used is not the same as for potable water systems. Heating systems require an Oxygen barrier so that O2 can't permeate through the tubing into the system. (and it WILL, believe it or not!) O2 is corrosive to ferrous metals in the presence of water... not good for your system.

There are a few types used for heating... PEX-AL-PEX has an aluminum layer sandwiched between layers of PEX and is nearly as O2 proof as possible. But it is NOT as flexible as one might think by looking at it! Others have a coating applied to the tubing. The Onix that was mentioned may be the easiest to work with, probably the most flexible... one big plus for DIYers who haven't pulled tubing before is the fact that it won't kink. If you kink regular PEX, you have to cut and splice with a special coupler. Onix doesn't care... and termination is probably easier too...

The big thing with underfloor though is the insulation, as rbeck mentioned... you want the heat going UP to the floor, not down. And the cavities with the tubing should be mostly air tight...

If you suspend the tubing in the cavity, I think you could get by without the mixing valve and just run the regular boiler water through the tubing... you aren't looking to HEAT the space as you said... only to warm the floor a little... I don't see any need for any 'controls'... let the tubing warm the floor whenever there is a heat call... Onix will take the heat... (others will too)... thing about using full boiler temp water is that you might actually end up OVER heating the room... which is why I believe rbeck was suggesting the controls.

[Just looked at the Onix install manual again, and they recommend that Onix always be in contact with the floor... not suspended... so I think you would need a mixing valve as rbeck suggested... and dial in the water temperature that works for you... ]

Browse around PEX - Radiant Heat - Radiant Heating - Plumbing Supplies - PexSupply.com for information... I don't think they carry the Onix though...
 

Last edited by NJT; 01-29-10 at 06:46 PM.
  #8  
Old 01-29-10, 06:28 PM
Member
Join Date: Nov 2005
Location: USA
Posts: 2,459
Received 0 Votes on 0 Posts
  #9  
Old 01-31-10, 07:05 PM
Member
Thread Starter
Join Date: May 2007
Location: New Jersey
Posts: 193
Received 0 Votes on 0 Posts
Thanks guys.. all very interesting and helpful stuff. That doc was great.. I think this is totally doable (though I may wait till the spring when the heat is off to not freeze out my family when I drain the system )

I am wondering if the radiant floor subsystem will lower the water temperature to baseboards downstream (most of the house including the 3 bedrooms are all downstream)

Sounds like the radiant heat doesnt need too high a temperature. I may want to mix the return back in cool it a bit. (especially since I'm upstream)

I'm trying to figure out what setup I have in relation to those diagrams. My house is a single zone that has one larger diameter pipe from the boiler that circles the basement.. then smaller copper pipes shoot out and back to the radiator.

Thanks again. All great stuff!
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: