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Author: BeenFooled Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 128800  
Subject: DIY Radiant floor? Date: 11/27/2006 12:49 AM
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Anyone here done this? (I'll get to you in a minute Goofy :-)
The area is about 200 sq. ft., rectangular, most of it new construction (sunroom add-on). I am working with a contractor to do the construction, but he is OK with me biting off pieces to do myself. I am considering this as one of the pieces, since he got a bid from a plumber for the best part of $5000, including a new water heater (see previous thread) and running its flue up 4 storys (which can't be fun).

Anyway, I knew Goofy had done it and I remembered the story, thanks for the link refresh though. What I did not remember was your source of PEX and how you'd fastened it, etc., and now I see that you used copper. I don't think I want to do this in copper (although your comment about heat transfer is well taken! - and I am perfectly comfortable sweating copper), I think I'd like to use PEX - mostly because the whole thing will be set into 1.25" or so of mortar under tile, and I am afraid the copper expansion will lead to mortar bed failure in short order - somehow PEX seems to me should be able to handle this more gracefully. Or am I wrong?

So if I go down this route, I have a few questions....

(1) it seems to me that you don't want to start at one end of the floor and wind your way around in an orderly scan to the other end, or you'll end up with very uneven heating. Do people then run multiple separate coils from a manifold all the same length (like you do to balance dripper hoses), or do you come up with a clever pattern to make sure things wind around in a way to warm up evenly? Are there such standard patterns somewhere or does one just make it up?

(2) where to get the PEX?

(3) should I bury it in mortar, or should I try to run it under the floor so I have access to it if it fails?

(4) what do I need in terms of pressure and temperature valves and gauges in such a system? Expansion tank? I saw the air bleed thing and check valve mentioned in Goofy's story. A few of these little widgets and before you know it the plumber's bid doesn't seem so high.

Anything else I should think about before I fire the plumber?

Goofy, re: stagnant water, did you see my post where I found out that you can in fact engineer a simple bypass valve that lets you drive the cold water back through the floor in the summer on its way to the HWH - therefore there never is any stagnant water (except as you say if you are on vacation for a while, but that's an even bigger problem with the potable cold water, and I always run it awhile upon return anyway - I am sure everyone does).

Thanks
BF
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Author: Goofyhoofy Big funky green star, 20000 posts Top Favorite Fools Top Recommended Fools Feste Award Nominee! Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83759 of 128800
Subject: Re: DIY Radiant floor? Date: 11/27/2006 6:41 AM
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Anyone here done this? (I'll get to you in a minute Goofy :-)

Can't wait. Sorry ;)

A couple thoughts. You could do this with electric heat mats for about half the $5000 quote (and your own labor. It's easy, I did Mrs. Goofy's bathroom this way.)

including a new water heater (see previous thread) and running its flue up 4 storys (which can't be fun).

Electric water heater. No flue required. As you saw in my link I even have a "local" HWH, just a 10 gal version, which sits under the sink vanity and produces all the water I need for the radiant flooring. Cost around $100, IIRC.

I used copper because I knew nothing about PEX, nor had the tools, nor any experience. I couldn't find any DIY with PEX at the time, either. Of course I was running it through rafter spaces and not heating a thermal mass, so the situation was different.

(4) what do I need in terms of pressure and temperature valves and gauges in such a system? Expansion tank? I saw the air bleed thing and check valve mentioned in Goofy's story. A few of these little widgets and before you know it the plumber's bid doesn't seem so high.

The air bleeder was maybe $5, the check valve another $20. I don't have an expansion tank, nor temperature valves, nor pressure valves, so all the rigamarole (fittings, nipples, etc.) couldn't have been another $30. With the closed system, and the air bleed thing at the highest point, any excess pressure bleeds out as air (I have a drip pan underneath, I occasionally see a couple drops of water, which evaporate in short order). My recirculating pump has "temperature settings" which start and stop the water flow at prescribed temperatures.

I use a $10 Intermatic timer to run the pump, so I make "floor heat" from around 5AM to 10AM in Spring and Fall (none in summer), and run it 18 hrs/daily in winter to heat the room. I let the HWH run all the time (except in summer) and just control the pump to limit the amount of heat I transfer from the HWH to the floor by pushing hot water around.

I considered getting a cheap bi-metallic thermostat for the room and wiring it to control the pump, but it has been unnecessary.

Goofy, re: stagnant water, did you see my post where I found out that you can in fact engineer a simple bypass valve that lets you drive the cold water back through the floor in the summer on its way to the HWH - therefore there never is any stagnant water

I had it in the plans to do that, but when I moved the HWH heater under the vanity I didn't want to lose the additional space on one wall, so I bagged it. As it turns out I realized that even with a bypass, the level of the piping is below the rest of the bathroom, so when you "shut it off" it doesn't drain, it just sits there anyway. With a discreet system it doesn't matter - but I do a flush before I start it up each Fall anyway; it takes 10 minutes and a 10 foot length of garden hose which I run over to the tub for drainage.

The one downside to this sort of radiant heat is the lead time; it takes at least an hour, preferably two to get the water to heat the air space to heat the subfloor to heat the tile to a comfort level. Mrs. Goofy's thermal mat comes up to temperature in about 5 minutes. It was also child-simple to install. Best, I put one of those "twist-to-start" timers on the wall next to the "intended" control, so she just twists it "on" and it automatically goes off an hour (or less) later. She loves it.

(1) it seems to me that you don't want to start at one end of the floor and wind your way around in an orderly scan to the other end, or you'll end up with very uneven heating. Do people then run multiple separate coils from a manifold all the same length (like you do to balance dripper hoses), or do you come up with a clever pattern to make sure things wind around in a way to warm up evenly? Are there such standard patterns somewhere or does one just make it up?

I don't know any of this, but I do know they talked about "heat striping" when doing PEX tubing in concrete. The heat doesn't travel far horizontally through the concrete, so if the lines are too far apart you get stripes of hot versus cold, which isn't good. Since mine heats an air cavity the heat seems to spread more evenly. I recall one "This Old House" about radiant heating where the guy did have a manifold and several zones, but I don't recall if that was for different rooms or to balance a single room.
 


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Author: FoolYap Big funky green star, 20000 posts Feste Award Nominee! Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83761 of 128800
Subject: Re: DIY Radiant floor? Date: 11/27/2006 7:23 AM
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I don't know any of this, but I do know they talked about "heat striping" when doing PEX tubing in concrete. The heat doesn't travel far horizontally through the concrete, so if the lines are too far apart you get stripes of hot versus cold, which isn't good. Since mine heats an air cavity the heat seems to spread more evenly. I recall one "This Old House" about radiant heating where the guy did have a manifold and several zones, but I don't recall if that was for different rooms or to balance a single room.

FWIW, the contractor who added the hot-water radiant subfloor in DW's room over the garage (approximately 250 square feet) used a manifold, and split the floor into three separate zones. Not to be controlled independently, but to balance the room. He said if the room were done with a single zone, the temperature-drop of the tubing across the length of the room, as the tubing snakes back & forth across the length, would be too much to adequately heat the far end.

He also paid attention to the insulation in the garage ceiling below the floor, in the room's ceiling, the rooms walls, the number of windows, etc, to calculate a flow-rate through the pipes sufficient to handle the heat-loss everywhere. That may not matter as much in most installs, but we were pretty far from the boiler, and he was concerned about the diameter of the piping that had already been run near the room (by the builder, for "future expansion"), as well as the size of the pump that is used for other radiant floors in the house.

If we didn't already have HW radiant floors elsewhere, I'd sure have considered electric radiant for that one room.

--FY

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Author: otter6 Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83762 of 128800
Subject: Re: DIY Radiant floor? Date: 11/27/2006 7:33 AM
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doing it ourselves.... will be using PEX, woodfired Central Boiler as the heat source...

following are links to "websites" associated with Radiant heat.... lots of ideas, concepts such as how to run the tubes, etc... Everything you need to know is out there... and after you read this stuff, visit one of your local "installers/dealers" and pick their brains for the questions you need clarification on... The "supplier" I am using has been very willing to answer any question I have thrown at them cause I am buying my parts/supplies from them (note, they are about breakeven with the NET prices... if they weren't, I would be buying off the net almost all except the PEX (if there is a hole in it, I want to deal with the supplier directly and immediately)... good luck...

lots of info at these sites:

http://www.houseneeds.com/Shop/HeatingProducts/RadiantHeating/safelink/safelink12inchbuy.asp

http://www.radiantdesigninstitute.com/page23.html

http://www.radiantdesigninstitute.com/page2.html

http://www.radiantdesigninstitute.com/page3.html

http://www.mvsupply.biz/radiant_heat_design_guide.htm

http://www.houseneeds.com/Shop/atop/radiantheatingindex.asp

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Author: otter6 Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83775 of 128800
Subject: Re: DIY Radiant floor? Date: 11/27/2006 11:44 AM
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some key info I gleaned for my installation?

if you have more than one loop, make sure the multiple loops are the SAME length. Has to do with "delta p" across the loop and balanced flow.

the pattern is important to make sure you direct the heat to where you want it the most

the length is important because if its too long, you will end up with water that is too cold at the end of the loop.... heating suffers

if you have hardwood flooring, radiant heat is not "encouraged" as a direct source of heat to the hardwood... has to do with shrink and swell of the hardwood.

if you put the tubing into concrete such as say a slab? consider insulating under the full slab to decrease the loss of heat to the soil....

just some bigger picture items.... that may not be obvious unless you read the fine print...

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Author: alaskack Big red star, 1000 posts Old School Fool CAPS All Star Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83783 of 128800
Subject: Re: DIY Radiant floor? Date: 11/27/2006 2:29 PM
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Try this link:

http://www.radiantec.com/index.php

They sell products and have installation guides and manuals you can download.

Calvin

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Author: bankingintern Big red star, 1000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83788 of 128800
Subject: Re: DIY Radiant floor? Date: 11/27/2006 6:25 PM
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I've been looking at this, in slab wiring. From my POV going electrical is far easier DIY and the risk of failure, and impacts are far lower. Also the cost is a LOT less than the $5k your

http://www.warmyourfloor.com/index.asp?PageAction=Custom&ID=10

If your pouring a slab for your addition, you can simply add the cable before the pour and you'll be good to go.

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Author: otter6 Big gold star, 5000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83791 of 128800
Subject: Re: DIY Radiant floor? Date: 11/27/2006 9:09 PM
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there is also the "after installation" operation costs of providing the SOURCE of heat...

isn't electrical one of the least efficient/more costly ways to heat with versus NGas, fuel oil, or wood (that in my case, will cost me the gas to run the power saw and tractor to bring it in)...

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Author: lowellches Three stars, 500 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83793 of 128800
Subject: Re: DIY Radiant floor? Date: 11/27/2006 9:43 PM
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more radiant info:

http://members.aol.com/miffedone/Radiant.heat.floor.1.html

http://www.warmlyyours.com/homeowner/index.aspx

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Author: bogwan Big red star, 1000 posts Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83799 of 128800
Subject: Re: DIY Radiant floor? Date: 11/28/2006 9:16 AM
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I have read about electrical systems.

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Author: bozob Big red star, 1000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 83832 of 128800
Subject: Re: DIY Radiant floor? Date: 11/29/2006 10:53 AM
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One suggestion is to contact your local HVAC/heating supply places. At least one of them will be a supplier of radiant heating products including PEX and all the neccesary valves and manifolds. Plus they'll probably have someone on hand who has some basic knowledge of this stuff.

bozob

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