Radiant Floor heating within a finished ceiling/ floor.

[Rooster]

Hey guys,

I am in the process of designing a TF Barn conversion, into a living space/ farm office.  I am adding interior lofts within the two end bays/mows.  I would like to heat the building with radiant floor heating, utilizing a OWB with a LP boiler backup. I want to divide the building into multiple zones.  I can install the tubing under the first floor from the basement/ milking parlor, but I am looking to "sandwich" the tubing within the layers of the loft floors.

The sequence that I am concidering is as follows:

Top down:

3/4 in re-claimed maple flooring
3/4 in plywood subfloor
3/4 in x 6 in firring strips positioned over joists, with tubing running between strips
3/4 in T&G car-siding (pretty side down and seen from the first floor living space)
6 x 6 ceiling/floor joists

 



Some ideas that I have been playing with are:

~Using 1/2 in tubing for flexiblity, making a single loop between floor joist spacing.

~Using thin reflective foil insulation under tubing to push heat up through floor.

~Using thin radiant tin plates to spread the heat to a larger surface under subfloor.

~Standardize tubing placement to allow for accurate nailing patterns for hardwood floor installation.


I am looking for anyone's advice, opinions, and encouragement .

Thanks!  In advance!

Rooster
 

[Jim_Rogers]

Have you discussed any of these ideas with a professional radiant heating person?

[Rooster]

I have spoken with one, but since it didn't look like a "duck" or quack like a "duck" he wasn't interested in geting involved.  I will probably contact others in my area, I just wanted to have a preliminary plan to show them, and I don't want to have to "re-invent the wheel" everytime start a unique project.  

I am just looking to see if anyone has done something like this, or if I am missing something in my initial design.

Thanks,

Rooster

[Ron Wenrich]

I put in a Stadler system about 15 years ago when I converted my summerhouse into living area.  I'm running an oil burner, but your application would probably do as well.  I put it over the subfloor, then there is a 1/2" plywood series of grooves that you put plex tubing in, then the floor of your choice.  In the bathroom, it went under concrete board and ceramic tile.  Nice and toasty.  In the rest of the area it went under a 3/4" cherry floor.  Works good, unless there is a hard wind.  Old house.

Stadler was a German company.  They seem to have merged with Viega.  I saw this system on This Olde House many years ago.

Here's some examples:

http://www.tjsradiantheat.com/radiantheating.html
http://eandemechanical.com/radiantheatinginstallations.asp
http://www.launstein.com/radiant-heat/radiant-manufact/radiant-manf-home.htm   Lots of links for what you're doing.

[beenthere]

Rooster
Appears you have sandwiched the heat into a thin 3/4" plenum with 1 1/2 inches of solid wood above. To me you have a well-insulated box around your heat tubes. I can't put my finger on it, but doesn't look like a good way to transfer the heat from the tubes to the room above.   It just seems....

[sprucebunny]

You might look at Reflex insulation. The foil-bubble-foil stuff. It would go under the tubing as they usually recomend insulation under the tubing. I have radiant under a 1" thick plywood floor and it works great. There's 3" of fiberglass under it.
The aluminum heat spreader plates are expensive.

When I did it, they recomended clips that held the tubing 1/4" below the floor. Not sure how you are going to position the tubing in a small space.

[shinnlinger]

I cut a 4 ft roll of armafoil (think tyvek tinfoil) into 6inch rolls with my chop saw and stapled pex tubing to the bottom of my main floor with an air stapler.  Reflective, Fast, Cheap and easy.

For my second floor of my timber frame, I put ripped 2x on center(1-1/2 x 1-1/2) on top of my 4x8 floor joists and then pre painted drywall and set them down in each bay form the top.  This created a 1 inch space which I will run pex thru before I put subfloor down.

Dave

[Holmes]

 Hi Rooster  Your design will give more radiant ceiling heat than radiant floor heat meaning it will heat both areas. You need to insulate below the tubing to drive the heat up thru the floor. Your floor has an r value of 1.8 the ceiling has an r value of .9 so the heat will go down. 1" of foam board under the tubing will work , double pipe each bay and suspend the pipe from the floor .  I can go into more detail if you like. I have installed hundreds of radiant heat systems.  Holmes

[Rooster]

Here is another idea.

From the top-down:

~3/4in. Maple flooring
~3/4in. Plywood cut into 12in x 8ft pieces with 30 deg. bevel to hold tubing.
~3/4in. T&G pine
~6 x 6 joist

 



I am thinking that I might be able to make my own radiant plates out or used printing press plates.

I am open to any number of ideas.  I guess I would like to keep the thickness of the floor system to a minimum and also maximize the effectiveness of the heating system.

Thanks for all the responses.

Rooster
 

[shinnlinger]

Rooster,

Did you see my post on the Arma foil?  You will not find a cheaper, easier way to radiate heat.  Sure you can make a jig out of plywood and smash rebar in your printers plates for a few hours and then cut and piece them together underneath one at a time, but with those rolls of foil(again, think tyvek tin foil) you just pinch the pex and staple away for the whole run between the joists.  A 1000sf roll was about $130 and I just cut it into 6 inch widths on my metal chop saw.  They sell narrow rolls for more money if you want.

For your second floor, put the foil down underneath your pex.  

Dave

Dave

[ballen]

Hi Rooster,
Look at:
www.warmboard.com
It's basically plywood subflooring with the pex grooves pre-cut and the whole thing covered in aluminun.  Get's the heat right up just under the finished flooring.
I have a sample and it looks pretty good.
Bill

[shinnlinger]

I wonder how much that warmboard costs?  Looking at it though, I will suggest that you can lay your v grooved subfloor as planned and then roll out the entire 4 ft wide rolls of arma foil and then press your pex down into your grooves. 

[Holmes]

   Warm board is a designed system . You show them your layout  they design and sell you the way to lay it. It's 1 1/8 in thick and is the sub floor. $$$$   Your second design is better. You can use shinnlingers idea or put 6" aluminum flashing down under the plywood  centered on the opening and then silicone the tubing to the aluminum.  Ideal spacing is 8" but if you are well insulated you can do 12" .You should  use tubing with an oxygen diffusion barrier to protect your indoor boiler. 1/2 " tubing max overall length is 400'. you will still get some heat migration down to the rooms below without some type of insulation below the tubing and that may make it difficult to control the first floor heat.  Now if you have a room that needs additional heat you can put in radiant floor and radiant ceiling heat, or you can put it in a wall.  Viega and Upinor make a staple down product that 5/16 tubing fits into 7"X 48" about $11 each also quite expensive.  Holmes

[red oaks lumber]

is a 6x6 2' on center strong enough to carry that load with out bouncing when walking across your floor? depending on the span a 4x8 will give more strength. just my thoughts

[Rooster]

Thanks guys. This kind of feed back is just what I was looking for!

Bill,  I did look at the warmboard.  That looks really slick!

Dave,  What kind of Arma Foil did you use?

Arma Foil
Arma Foil VB
RB-RES
http://www.energyefficientsolutions.com/rbproducts.asp

Holmes, You have taught me that I have a lot to learn.

As I take in all these ideas, I am curious to know if I were to:

~ Nail down the T&G pine ceiling boards
~ Cover pine with a layer of the Arma Foil
~ Nail down the beveled plywood sub-floor
~ Lay 8in strips of foil over the grooves  
~ Push plex tubing into grooves, trapping foil
~ Install hardwood flooring

Am I getting closer?

I also wanted to describe the building layout.  The barn is a 28ft x 40ft three bay timber-frame.  The first floor will be fully open except for a couple of small rooms (bath, storage) with a couple of heating zones, and will be used minimally. I can access the first floor from the basement.  The center bay has a cathedral ceiling with a possible wood burning stove.  The west end bay will have an open loft with a heated floor with it’s own heating zone.  The east end bay loft (14ft x 28ft) will be used the most as a farm office/study.  It will have a partition wall separating it from the center bay.  The height of the first floor ceiling below the loft is just under 8ft.  It is this bay that I am trying to design the heated floor system for.

Rooster

[shinnlinger]

I used the foil as I didn't need the vapor barrier, but the rb res looks even cheaper and should be just as effective.  Maybe ask if it is as malleable as as the foil.

[Holmes]

 Looks good to me . You could put the foil under the plywood for the tubing  instead of on top. It's job is to help get the heat out of the pex tubing and spread it across the floor.  Holmes

[shinnlinger]

Here are some shots of what I did.  I ripped 2x4 in half and nailed them OC on the top of my joists(4x8).  This created a space that I put prepainted strips of 5/8 sheetrock.  Saved a ton of afterward ceiling painting and was way cheaper than cardecking, and who needs to look at a wooden ceiling in a timberframe?  Also reflects light better.  The big plus though is  it also left a 1 inch space that I can run pex and wiring in.  Subflooring will go on the riped 2x

[Rooster]

Dave,

That made a nice looking ceiling!

What did you use to position the tubing between the drywall and the subfloor?  Did you use any radiant plates to spread the heat along the underside of the flooring?

Thanks for your help!

Rooster

[shinnlinger]

I haven't put the pex down yet.  I was thinking of no foil because I didn't put enough pex under the main floor so ceiling heat wouldn't be a bad thing.  I figure heat rises as well and usually you want bedrooms to be cooler.

[barbender]

My FIL tried running his pex between his wood I joists and stapling Reflectix foil bubble foil insulation up under it. It keeps the heat from going down, into the basement, but it doesn't get the heat to radiate upstairs. In effect, the hot water just keeps circulating throught he circuit and doesn't transfer. You need something to transfer the heat, and some kind of insulation to keep it from going down below. I intend on pouring a 1-1/2"  concrete slab to run my pex in, over a 3/4" plywood subfloor. If you can build your floor to handle the weight of the concrete slab, I think this is the way to go. One other option I saw in a Menards flyer was a plastic grid you put down, and the pex snaps into it.

[frwinks]

I have spoken with one, but since it didn't look like a "duck" or quack like a "duck" he wasn't interested in geting involved.  

Rooster

I know the feelin'... just had three local HVAC contractors try to understand my house last Thursday.    It was the most pain I've endured since starting the project.  Seems terms like thermal walls, solar heat gain, superinsulated walls and ceilings, airtight construction, etc have not made it's way into the code yet  
I was given quotes for equipment, three to four times the required size
They wouldn't have my "heat the basement slab, bypass the main floor all together(I have two thermal walls, hi performance glass, wood stove and super tight construction), minimal baseboard radiant upstairs" way.  All that after they felt how the house feels right now, with a 1000W bulb and minimal heat leakage from the basement.

I replied over on TFG, but here it is as well
All of the foil insulation products need airspace to do their thing. Sandwiching it between pine and plywood will not give you the desired effects.
How about
-heavier pine ceiling
-1" or 1.5" of Polyiso insulation with routered out pex channels
-printing plate transfer plates
-heavier finished floor

[Holmes]

Rooster   I should have said this earlier. You should have 3 times the r value under the tubing than the r value above the tubing.  1" wood above is an r .8 so you need r 2.4 below the tubing to 'DRIVE' the heat up  toward the space you want to heat.   Holmes

[Rooster]

Throughout the majority of the postings there are three main ideas:

Insulation, Reflection, and Radiation

Am I safe to suggest that Radiation is the best way to draw the heat from the tubing and transfer it to the floor surface? 

And that Reflection and Insulation help increase the efficiency of the heating system?

So would the Arma Foil be more of a Reflective element than a radiant? Or is there enough mass in the foil to transfer heat as a radiant element of the system?

Sorry for all the newbie questions, and I appreciate all the input.

Rooster

[Brad_bb]

Craig, granted, I've never installed a radiant in floor heat system myself, but it seems to me that the main term we should be considering is Conduction.  In a concrete floor, the tubing conducts directly to the concrete, which is good as a large thermal mass can hold the heat and release it gradually.  In floor systems, I've seen special aluminum plates used to conduct the heat from the tubing to the underside of the floor.  The conductive aluminum plates spread the heat out across the floor surface so as to more evenly heat it and not have hot and cold spots.  The purchased plates are good because they are formed(probably extruded) to allow the tubing to snap into them and have more contact area for conduction.  What I've seen done, especially in retrofit situations, is to affix the aluminum plates to the underside of the subfloor.  Typically in a joisted application, you have a cavity between the underside of the floor and the ceiling of the floor below.  They'd typically insulate that space to make sure all of the heat went up into the floor you're trying to heat.  The heat will naturally want to go up, but the insulation helps direct it even better.  

  I understand that you don't want a significant cavity below as you want the timbers exposed.  You would like to lay your ceiling wood on top the the floor joist timbers first for convenience, but my suggestion would be to lay your spacers if desired, or your subfloor first.  Then attach your conductive plates to the underside of the subfloor and run your tubing.  Then install the ceiling wood below, with short pieces between joists-probably loose like a false ceiling.  You could even do paneled sections to ease installation. You could leave a small space for a little insulation.  The ceiling below would be installed like a false ceiling, either on support rails, or timber would be knotched or whatever.  The benefit to this would be to allow you access to the floor heating system from below later if you ever had a leak or puncture, or if it needed to be replaced.  I'm not sure how long that tubing is rated for in use, but I'm sure it's less than the house life.

  The way you suggested would necessitate tearing up the whole floor to access the radiant heat system, no?  This isn't my idea, I think I got it from Thomas Massie and watching what he did in his house.  I'll have to go back and read his blog again to find his details.  He would be a good one to run this by too.  I think I have his new email if you need it.  Brad
http://massiehouse.blogspot.com/

[Brad_bb]

Here's a pic.  Where I have the wood bracket for holding the ceiling, you could also a)cut a groove in the timber to insert the panels, or b) space the floor up enough(like with 3 or 4 inch spacers) that you can set the ceiling panels on top of the floor timber.  Check out January and February 2007 of Thomas Massie's blog.  His floor system is slightly different from what I described - a framed 24 system on 12 in centers, but as he states, has zero bounce and gives him the space needed to run the tubing.  I don't see how he finished the ceiling below, but we can ask him. Brad

[ReidH]

I will be doing the following on my TF addition for heated flooring this year.

2x6 TnG subfloor on top of the joists.
 
3/4 inch plywood strips about 6.5 to 7 inches wide spaced to mount the heat transfer plates on top.

Heat transfer plates, such as Thermofin on top of the plywood with Pex-AL-Pex tubing.  The reason for the Pex-AL-Pex is that it has a coefficient of expansion that is equivalent to aluminum, which is what the heat transfer plates are constructed of.  If you use regular Pex, the expansion rate is much higher than the plates and when the tubing trys to shift position, you will hear squeaks.

Hardwood finish floor on top of that.

For insulation I am adding the following on the underside between the joists:

2 inches of rigid insulation protected with drywall on the underside of the subfloor.  The joists will look to be a little shallower than they really are, but you can use the 2"  insulation space to conceal runs of wiring for ceiling mounted lights/chandeliers as well.  You could use TnG instead of drywall for the finished ceiling as long as your rigid insulation is provided with adequate fire protection.

Reid

[Holmes]

Brad_bb  Pex tubing will probably outlast the house. The rubber hose type tubing will not.  Your design is a good one as is ReidH's. 
Heat transfer plates are great at getting the heat out of the tubing and into the wood and is the best way to go if you are not using concrete or gyp-crete.  Holmes

[Brad_bb]

I've learned the hard way that if you don't build in a way to service it, then for sure there WILL be a problem and you'll have to tear it all up.  I wouldn't trust it for over 100 years.  We have houses that have lasted longer than that, and if it got to that point, I'd want to be able to service or replace the system.  Though, we'll probably have home fusion heaters by that point that are smaller than a toaster.

[witterbound]

Do they still make radiant hot water heaters that hook up to a boiler, like in the old days?  It sure seems like this would be a better way to heat your upstairs, than going through all you're planning under the floor.

[Thehardway]

Radiant hydronic heating wood floors makes for a very comfortable house if done correctly, however, since wood is a relatively poor conductor of heat, it is not a very efficient or economical means of heating and unless you have a low cost fuel source (such as waste wood products or solar collector).  Locating piping too close to the floor surface can causes a "striping" effect.  The heat does not spread out effectively as it conducts through the wood, this is often the case with floors that utilize channels or strapping on the sub-floor and directly under the finish floor.  Water temps must be kept very high for radiant heat through wood 120 ^ because of thermal inefficiency.  This can cause excessive shrinkage and movement or warping.   Too low in the floor and it bleeds through the ceiling below as previously mentioned.  This causes more inefficiency and causes rooms below to get too warm in the head space whilst cold at the feet.  This is bad.  You can see a delicate balance is required.

You would probably be better served and it would be more economical to use hydronic radiators for such an application and strategically place them in the space to be heated and allow natural convection to do the rest.

I like radiant floors under concrete, gypcrete or tile but I have reservations about under wood. 

At temps needed for radiant through wood, you will need to use oxygen barrier pipe or use all non ferrous circ. and heating devices to avoid problems as well.

[DouginUtah]

I agree with most of what Thehardway has said . I used PEX in my basement slab spaced at 1', which turned out to be overkill--it would have been overkill even at 18". But for my main floor I used slantfin  (www.slantfin.com) baseboard heaters (at about 3/4 the lengths recommended by their heat loss program) and if I set the thermostat at 70 it never varies more than 1/2 degree. This is for new construction with very good insulation.

[Holmes]

 I do not agree with Thehardway. Radiant heat is a very efficient way to heat a house if it is installed properly.  Striping is caused by poor installation. water temps in the tubing above 120* f are the result of poor installation. Systems with these problems need heat emission plates or suplemental  heat, like X amount footage of baseboard  radiation.   Radiant heat does not cause shrinkage in the flooring, a lack of moisture in the wood causes shrinkage.  Unless you install humidification in the dwelling the wood will shrink no matter what you have for heat.
  Baseboard  Radiation is a good way to heat.. It cost a lot less than radiant heat to install and if you want to use lower water temperatures just install twice the amount of base board radiation and run 130* water thru it...For every 3 degrees the water temp. is lowered you have a potential for 1% savings in fuel.  Holmes
 

[beenthere]

I'd have to side more with TheHardway on this. Holmes has missed a few points in his side of the discussion. But thought TheHardway outlined it quite well.
No offense meant to Holmes, just sayin.

[Thehardway]

Holmes,

Not trying to pick a fight here.  I agree with most of what you have said but there are a few key things that don't ring true.  Efficient radiant heat depends on goodly amounts of thermal mass.  Aluminum, steel, concrete, tile etc. all do very well at absorbing, conducting distributing and radiating heat over a period of time and space.  In radiant applications this means that the tubing can heat the floor that the tubing is in contact with and once it is up to temp it will stay there for a significant period of time.  It does not lose it's heat rapidly like air, and therefore does not require constant heat input and circulation.

Hardwood works better as an insulator than as a conductor or thermal storage mass. It does not absorb heat well nor conduct it well.  It burns before it heats through. This is precisely why they used to put wood handles on pots and pans.  Barbender relates an experience representative of this.  Can it be done? Certainly, but it is not near as efficient as it should be and not from lack of proper install, rather the property of materials.  You won't find many wood radiators out there nor wood heat sinks because of this particular inefficiency.  If one insists on warm floors, then it can be done but it is not near as economical as some other heating methods and they must be willing to accept the tradeoffs.

The other point I might make is that any honest wood floor installer or radiant heat installer will tell you up front that you can expect significant seasonal movement in the floors and there are several reasons for this.

The most obvious one you have already pointed out but with the wrong conclusion.  Humidity.

In a house heated with hydronic radiant heat, there is no consistant source of humidity.  If it is properly installed, the water stays in the tubing.  This means that the cool air in the home becomes extremely dry in the winter and heated by the floor rises as natural convection carries away the moisture in the wood very rapidly.  Conversely, when the heat is turned off, warm moist air in the house deposits its moisture at the floor which stays slightly cooler and condenses and absorbs the moisture like a sponge, swelling as it does so.

In order to adequately control the seasonal humidity changes, a secondary humidification/de-humidification system would be necessary.

Wood being hygroscopic in nature does not dry on its own past a EMC of approx. 10-12%.   EMC does change after EMC is obtained with changes in both relative humidity (a function of temperature) and to a lesser degree with temperature alone.  If relative humidity is not elevated as air temp is increased, wood will give up its moisture and become dimensionally unstable.
Those who kiln wood are keenly aware of these properties. 

Guidelines for installing hardwood floors over radiant heat do exist but meeting them to ensure a stable floor adds significantly to the cost of the floor.

Here are a few of the reccommendations:

EMC between 6-8%
t&g boards less than 3" in width
beveled edges
quatersawn boards
thinner boards better than thicker
acclimate wood and install at average seasonal relative humidity
provide for seasonal alternative humidity control system

This is not my opinion but that of flooring manufacturers.

I agree you can run water temps lower to avoid striping effects but you also limit your overall output and increase cycle times once again decreasing efficiency.


I love radiant heat, I hate squeaky or warped hardwood floors

[Don_Papenburg]

Rooster , My plan is for 3/4 sub floor  5/8 strips 5.4" wide . that gives me a 6" tube spacing  using 1/2 pex.       I would not space tubes more than 6" apart .  As was mentioned previous it would leave a thermal striping effect.  I would like to run 3" under wood but I can't get a bend tighter than 6" .      I have my basement on 6" centers over 2" EXP with 4" concrete over.  I keep the basement at 70 F. and it will keep the first floor 60 F.
The six inch tube space lets you run a lower water temp.  I try to keep mine at 120 in and 100 out. 

5/8 ply is about the dia. of 1/2 pex .  I think that you could lay the all foil over the top with the 5/8 ply strips  because that will let the foil contact the tube without the U shape.

[Rooster]

I want to thank everyone for the "lively" debate.  I will be working with a local heating contractor, and I have asked him to take a look at this thread.  I will post the details of the the system that we will be using, and I encourage others to post their radiant floor projects along with the pros and cons of each application.

Thanks again,

Rooster

[stumpy]

Hi Craig. Go on line to a company called Radiantec.  They are very helpful and they will put together a heating "scheme" including parts list for free.  Granted, yours is not a typical installation, but I found them very helpful and accommodating.  They also sent me a packet of info along with the parts list.  There's a booklet that is very informative about the different method of radiant heat.  I was going to build a shop building with radiant heat in the floor.  They highly recommended using a standard LP water heater.

[Holmes]

   I was going to build a shop building with radiant heat in the floor.  They highly recommended using a standard LP water heater.

                   
The water heater can do the job but they are only 70% efficient. A good boiler can be 95% efficient. You could be losing 25% of your btus out the flue, so very every $4 you spend on a gallon of fuel $1 goes out the flue. Give it time and cold weather and a lot of money will be thrown away. Holmes

[D Hagens]

  I've installed miles of pex for radiant heating and it's an awesome and very efficient way to heat ones home This is a very detailed discussion and there's some very good points brought up.
 Now here's something to think about.........I would never install this in my house ever The reason why is because I don't like the feel of the heat, it's a different feel to me compared to forced or the above floor radiant that I've been used to.
 It's always a question I will ask a customer before I will install the product.

[frwinks]

ha, I found it.  The detail I tried explaining in my earlier post came from Rupert Newman's Oak Framed Buildings.  I just stumbled across it again this weekend and remembered this thread. What I like about it is the no nonsense approach, just the stuff you need without redundant layers of ply, stapping, nailers, etc..

[Brad_bb]

Too small Rafaelfrwinks.  We need a cropped close up please.

[frwinks]

hope this one is better