proper technique for radiant heating
Building a home and considering putting radiant heat in the lower level and the main level of a two story walkout (only putting radiant upstairs in master bath). My question comes from the pluses and minuses of putting radiant heat under hardwood floor in kitchen and hallway of main floor. The floor will be 3/4″ oak or hickory. Plumber suggested we gypcrete main floor putting piping in the gypcrete. However, GC wasn’t high on that due to the hardwood floor installation. He suggested putting up under the floor joist and then using the metal backing to radiate the heat upward. I can see several issues here from additional cost to install piping this way and also less effective “heat” when it has to go through sub floor and the wood floor itself.
All responses appreciated, I only know enough to be dangerous!!!!
Be the way live in se minnesota (thus we NEED heat!!)
Replies
Yeah, you need the heat almost as much as I do.
Ideally, your GC AND your plumber would agree on an installation. Since they both (and you) need to deal with it.
General info: Medium mass systems (gypcrete) are slower to respond to chnages in amibient temps, solar input or setpoints (setback to save energy, rise temps after vacation, etc). But gypcrete makes a great heat exchanger with very even heat distribution over the floor.
Low-mass systems (aluminium fins under the flooring respond quicker but cost a fair bit per linear foot. At least the framing doesn't need to be beefed up.
Hardwood? For the hardwood to disipate XX BTU/hour, it has to be a certain temperature regardless of whether it got to that temp from touching concrete or aluminum. So shrink/swell due to humidity changes is the same in either system.
I'd base the decision on the expertise of the installer (DON'T be on someone's learning curve). And secondly on cost. Either approach (gypcrete or aluminum fins) would work fine for the main level.
To maintain constant sub-floor heights probably suggests Al-fins on the upper-floor bathroom. And the low-mass nature of it allows an easy time-of-use thermostat so you have warm toes in the morning.
As usual everything DT said is correct.
I retrofit radiant into our last house... got in the crawl space and installed tubing 8" on center under the subfloor (7/8" fir subfloor with 5/16" oak strip flooring over it, except two rooms with 3/4" oak t&g flooring). After installing the tubing I insulated (R19) between the joists leaving a 2" air space above the insulation and below the subfloor. Ran 135 degree water thru the tubing and it heated the house nicely.
You need to consider the heat loss characteristics of your house. Our place was in a very moderate area of northern Cal and it doesn't take much to heat there. In MN it's a different climate. As I recall the max output of a floor is about 20 BTU per square foot. Is that enough to heat your house? You might need radiators as well.
Also... a good radiant forum at heatinghelp.com (the 'Wall')
For new construction, running in joist bays is probably not the best choice. More appropriate for retrofit.
Consider radiant subfloor panels like Warmboard or Veiga "Climate Panels".
http://www.stadlerviega.com/startpage.asp
http://www.warmboard.com/
I also live in SE MN and did a DIY sandwich (reasonable materials cost, much more labor than anticipated, great results). In order to DIY I did LOTS of research and found two forums that have really good info in thier thread archives...one already mentioned
http://forums.invision.net/index.cfm?CFApp=2
and:
http://www.radiantpanelassociation.org/i4a/pages/index.cfm?pageid=1
These two forums are as valuable to anyone considering radiant floor heat as BT is to anyone interested in lots of more general construction topics.
If you haven't spec'd your subfloor yet, look into Warmboard.
One way we do alot in new construction is to install the subfloor, then install 1" sleepers ripped from 2 bys. Install reflective bubble wrap, tubing, and have the tile guy do a wetbed between the sleepers. Run the heat to dry the wetbed, then Add hardwood floor to sleepers.
This works great if an entire floor is done this way-in terms of not having to match other floor heights, as you would have to use reducers otherwise.
IF you want floors at same heights, blast 2x3's to side of joists and cut plywood to fit in joist bays, put in wetbed, and inst. wood floor.
Like jonnyd, I installed my tubing in a DIY manner. I did'nt want to do a pin-up, nor did I want to pour gyp-crete with sleepers. I found the price of warm-board to be too costly so I made my own . Working with 3/8" tubing (1/2" O.D.) at 8" O.C. I ripped 5/8" CDX ply into strips, and fashioned end strips against the walls. In tile areas I used 1/2" cement board rather than CDX. Once the end strips and field strips were glued and screwed, I laced the tube in place, stapled it down and then filled the slots with gyp-crete. Put the hardwood directly upon the CDX , put carpet and pad directly upon the CDX, and applied a vinyl slip-sheet over the cement board and then limestone tile. We have been enjoying the radiant experience for over 1 year now with no problems at all.
Here's some installation photos for you.
good luck
Wow! Great pics! QWish I had the time and ability to do something like that. Tow your kids leaves me no time! Thanks for the reply!
Phil,
Looks good. Have done something similar. Couple of questions.
Why did you backfill the slots over the tubing?
How did you rout the cement board for the tubing U turns?
Thanks for the photos.
I've been researching radiant floor for three years, and these are the best, bar none, pictures I've ever seen of a DIY sandwich. Make my knees and back ache!
Several questions and comments:
How did you cut the Durock?
What supply and return water temps do you run?
What is your floor surface temperature on a design day? "Shoulder season" days?
Please describe and post pictures, if possible, of your boiler/manifold/t-stat/control system. single circulator and zone valves or one pump per zone?
Nice touch on the tubing around the tub rim!
Excellent use of materials, especially the use of Durock for sleepers in the tiled areas. I ended up using PermaBase over the 3/4" Advantech sleepers in the tiled bathroom.
Why the slip sheet between the Durock and tile? Advice I'm getting (and this is yet to be done, this weekend I hope) is to stick the CB down onto the sleepers with thin set, and probably fill the sleeper spaces with thin set as well, and then thin set the ceramic tile over the CB
JonnydThanks for the comments.1. Cut cement board w/ diamond blade on 4" grinder
2. Very low temp, around 100° f (I can verify w/ my rad flood sub)
3. I keep the house at ± 70° all day (me have no body fat)
4. Pictures included of my Munchkin Boiler and side H.W. tank
5. The house has 16 zones, w/ one circ. pump for the rad floor and on for the domestic H.W.
6. Used slip sheet (vinyl flooring) to minimize movement and cracking of tiles
7. Here's a picture of the m. shower tubing also
8. used jig saw on rounded wood end pieces to cut turns.
9. Used gyp-crete in the slots around the tubing to increase the heat mass and reduce creaking due to tube expansion and contraction.
10. Saved my back by using my senco collated screw gun w/ extention .
11. using Tekmar t-stats in each room/zoneCould'nt be happier with the outcome. No hardwood buckling or movement. No tile cracking. My gamble payed off!
Very similar in set-up, design, and results of my system, except I used AL plates.
Can you feel any striping barefoot?
Does that Munchkin modulate according to outside temp?
Care to share what the material, including boiler and distribution set-up, cost was per sq ft?
One concern I had with the concrete in-fill would be that it would crack in response to expansion and contraction of the pex, and then cause other problems but I guess proof is in the pudding.
I suspect with that many zones, your pump runs nearly constantly and that your steady state supply/return water temp is in the 4* to 8* range, and that you have a pretty well insulated and sealed envelope...all good things that seem to mitigate alot of the potential problems with radiant flor.
Thanks alot for your input on this...I suspect it will prove valuable to other pioneers.
1.Striping is barely detectable in the H.W. floor areas. Not detectable in the tiled areas.
2.The munchkin has operational limits based on outside temp.
3.Cost is unknown at this time. I did all the tubing layout and inst. myself. I payed cash to my sub for his installation labor. Payed cost+ 5% for materials including tax for all products run above board. It helps being in the industry, need I say more?
4.As I understand it, when the pex heats up, and is restricted from outward expansion, it expands inward thus no cracking or movement. I had the system up and running for over a month before cover, did'nt notice any cracking.
Thanks
Phil
I've said it before when you posted earlier pictures: that heated tub rim is awesome! Thanks for posting these photos. You have every reason to be proud of a superb bathroom and a nice heating system- without paying the big bucks for WarmBoard.
I'm still in a toss-up between running staple-up with insulation versus doing a DIY in-floor install like yours in my addition. I have to staple-up retrofit some of the existing house when I do the addition, so I might go this route for the addition also- but I'm still puzzling over it. I have existing rads to worry about, so I will have a more complex heating system design than you have regardless. But thanks for proving that a functional DIY sandwich IS possible!
OK, YOU . . . or your BATHROOM, are/is OVER THE TOP!
Did you do your tile work?
What are the slots in the ceiling above your shower?
How do you like your shower with a shower curtain, rather than the typical glass and doors? I think that is a nice idea. Keeps the room open.
No, I did'nt do the tile work, (have not the patience for that)
The slots in the ceiling are two of four pick-ups for the remote bathroom fan in the attic. Another is in the toilet room and the fourth is above the tub. Still need to make the trims.
Also the shower curtain is temporary, it gets two 3/8" glass side panels and a 3/8" dual swinging door (Agalite system)
Its been like this for about a year, and I'm really really anxious to use the steamer!!
Thanks for the feedback
Phil
Also the shower curtain is temporary, it gets two 3/8" glass side panels and a 3/8" dual swinging door (Agalite system)
Dang it, Phill, you said it before I could suggest it! I was looking at those pics thinking, "glass panels on the sides and a glass door in the middle." Just couldn't make up my mind whether I'd want to doors/panels to only go up to where the arch started, or to have them go up to the top of the arch.
Sounds like you're gonna use it as a steam shower, so I guess that means glass to the top.
And by the way, FANTASTIC bathroom! Visibly and functionally outstanding.jt8
Thanks JT8,The dynamics are such that we will have to have a square top door with a small header piece above, I would have liked to have an arched top door, however it would bind as it swings open. oh well.
The dynamics are such that we will have to have a square top door with a small header piece above, I would have liked to have an arched top door, however it would bind as it swings open. oh well.
That will look really nice. Functionally, as long as the stationary piece at the top isn't at nose height to you, you'll love it. An arched door probably would have put the pricetag through the roof, and the taller door would have made the door that much heavier.
Heck, I was afraid you were going to say you were putting art glass into the shower.. We would have had to come over and egg your house in that case (for having a BA that was nicer than my whole house) ;)
I've copied your pics into my 'ideas' folder. Shower layout, the radiant in the floors and tub AND shower... effective use of tile...etc. Very nice BA, very well thought out.
jt8
Edited 12/7/2004 11:50 pm ET by JohnT8
Now you have my juices flowing. Art glass? Hmmm. Say, does anyone know
if you can sand-blast or etch pre-tempered 3/8" thick glass?
WOW! Nice pics and a heated tub surround!
How did you cut the slots in the Durrock for the tubing? Looks so neat!
I pre-cut all the strips and end pieces with a diamond blade on my 4" grinder
before glueing and screwing them down. Then I layed the tubing in place and stapled it down. All is at 8" o.c. This way, layout is a breeze!
I really like your system. Do you have any idea how much weight this added? Are you in a cold area of the country? i.e. north east? Upper midwest? etc. I ask because I am. I am concerned that this system without AL plates, warmboard will not transfer enough heat on cold days. Thanks inadvance.
bob... all of the above posts are great.. me..
i'd probably go WarmBoard.. i've seen it installed and it makes a great subfloor for strip oak flooring..
Rick Arnold had a nice article using WarmBoard in the last issue of JLC
our last job was all RFH installed by the homeowner .. staple up from below.. or subfloor was TJI's at 16" oc.. and 3/4 Advantech ...
it worked pretty good.. but he spent a lot of time head scratching..
the Warmboard takes a lot of the guesswork out of the picture
Mike Smith Rhode Island : Design / Build / Repair / Restore