Radiant tubing above or below floor?
I’m a Mechanical Engineer building a new home in Massachusetts and it’s almost completely framed at this point. I want to use hydronic radiant tubing under the floors for heating. I’ve seen the Uponor PEX tubing and the quick track which sits on top of the floor, as well as the joist track that sits below the floor. I called Uponor and they said it doesn’t make much difference which type is used, but quick track is more expensive for material. Does anyone have any experience with installation of either of these types – would you rather do one over the other? Are there any pitfalls I need to be aware of? Are any other brands of PEX better?
I’m leaning toward the under floor joist track because I will have access to the tubing in the basement below, at least for the first floor.
Thanks,
Paul
Replies
Not to be too critical, but you already made the most common mistake in regards to radiant heating installation in a new home. You should have been planning heating systems before you framed in your house. The two systems you describe are more commonly used in retrofit applications than they are in new homes.
You have basically eliminated the three best options for in-floor heat....lightweight concrete, gypcrete, and Warmboard by not planning your framing to fit these systems.
In your case, I would probably now settle for the Joist Trak because it will not affect your ceiling heights and door rough openings. It is a good product, but no substitute for the above three in my opinion.
Anything Wirsbo-Uponor makes is good !!
BoJangles,
Thanks for the comments. I knew about Warmboard long before I started. I knew it was the best and I wanted to use it but it was way too expensive at over $6/sf for the board alone and I figured the payback period would be longer than my lifetime. It's a good product if money is no object. I'm also planning to put a masonry heater in the center of the first floor, so I needed to have money in the budget for that, especially because I get a lot of wood for free.
I did not want to to embed tubing in concrete because the large thermal mass makes the cycle time too long for daily temperature setback savings, plus there would be extra expense for structural support plus the cost of concrete everywhere. I wanted a fast feedback system, and I judged low mass aluminum/pex types to be second only to Warmboard in response time. Now I'm just trying to select a reliable product.
Paul
Your not going to get a quick responce from radient floor like you would a fin tube system. Generally you control it with something like a Teckmar outdoor reset , set the thermostat and let it go, for best comfort and savings.
I know that radiant systems have much longer lag times, but I don't know how long. I currently have a forced warm air system in my house and the programmable thermostat sets the temp to 60°F about 30 minutes before I leave for work in the morning. It starts to heat to 70°F about one hour before I come home. I was hoping I could do something similar with the radiant system to save energy, but the temperature change signals would probably have to occur several hours before the response. As long as the lag time between setpoint and reponse is less than the desired cycle time, it should be possible to setback the thermostat. All other things being equal, it is impossible to reduce energy use if I do not set back the thermostat. Leaving it at 70°F all day with nobody home is wasteful and does not make sense to me.
If you post your question over on the "Wall" @
heatinghelp.com
The experts there can give you a better explation.
From my expirence, In floor radient is more costly to install, but the most comfort and best cost savings in operation. Theres no comparison to a warm air system, you will love it, like anything else, if it's install properly.
I am also about to embark on a radiant floor heating project. I did decide to go with thin slab gyp. but did research alternatives. From what I understand you will want a heavier guage extruded aluminum product for the best performance and lower water temperatures. I'm pretty sure the joist-trac underflooor panel is just that. From what I understand the quick-trac above floor is not so great for the price. Have you checked out Rehau's Raupanel? Looks pretty great and performance is similar to warmboard I believe, but the price is probably up there near the cost of warmboard as well. Try addressing a post to NRTRob. He'll be able to tell you everything you need to know, he's not too far from you either.
BoJangles,
I'm sorry but I violently disagree with you regarding putting concrete over a floor as the "best"
several points
first such a system makes repairs nearly impossible, makes modifications nearly impossible, and gives you a floor of concrete.. stand on a concrete floor all day and your back will ache as well as your feet.
If you glue (because you can't nail) some kind of wood flooring over it you still won't be any better off.
Now I use concrete in bathrooms and kitchens where I will tile but for the rest of it I will put it under the floor
Frenchy, You can disagree, but you don't have to "violently" disagree. I'm just stating my opinion on which heating systems provide the most comfort in a home.
Hopefully you have calmed down by now!
My wife owns and operates a company that has been installing radiant heating systems since the 1950's. I am a homebuilder who has built hundreds of houses with lightweight concrete radiant floors and I can tell you for a fact that there is no other heating system that will provide that level of comfort.
You can install regular hardwood flooring, laminate, tile, or carpeting over these systems and be perfectly comfortable while enjoying the ultimate in radiant heat.
BoJangles.
I absolutely agree that in floor radiant heat is the finest way to heat a home. However I have severe objections to embedding infloor radiant into Concrete liteweight or otherwise..
I really understand what the differance is.. My grandparents had in floor radiant heat in their 1949 ranch home. The warmth was wonderful as well as lack of dust flying around from forced air.. However the strain on backs and feet was serious..
My currant home has infloor radiant heating done with a staple up system. In spite of massive over building to keep stiff floors there is no such back issues or sore feet issues. Plus service and access is relatively simple to achieve..
I have given my objections earlier and stand by them. Perhaps violently was the wrong adjective to use.
Heh, whatever keeps your feet warm!
I still think you should write a FHB article on your shellac floors.
Well,.... from my perspective it is the "best" floor I have ever experienced. Our house is all concrete, and was built to be very energy efficient. (ICF walls to roof, stressed concrete panels between floors with an overpour of concrete embedded with the pex tubing). It is the most quiet and comfortable house I have lived in, and I love the solid feel of the concrete floors. We have cork floors and almost everyone that comes in our home comments on how comfortable the floors feel on their feet. It is simply not true that you cannot achieve a comfortable floor using concrete.
As for the OP and the quest for using less energy, Perhaps you could make different choices that would make your home very energy efficient without relying on setting the temperature back and forth each day. Our house uses a fraction of the energy of any of our neighbours and the temperature is set at one point.. and stays there all winter.
Given the way you want to use your heating system, and your concerns on cost, perhaps radiant heat is not the best option for you. You seemed to be happy with how forced air functioned for you, so perhaps that is the way to go this time also.
Kivi
A couple of points. I have a SIP's house on ICF foundation so believe me I understand energy savings.. . I use in floor radiant heating for most of my heating but I live where temps swing well into the 40 below region. That plus I live where I have some great views and naturally I have a lot of windows..
Normally to offset the heat loss you crowd a lot of tubing below those windows in an attempt to metigate the heat loss but that makes the boiler/pump/s sizes go up dramatically to offset losses that may only occur a few days of the year. The rest of the time you are using a too big boiler/pump for those occasions when the system isn't capable of matching the your needs.'
My system uses a simple water heater to work rather than a more expensive boiler. Plus the energy use of a boiler would be much greater than the energy use of my water heater (not to mention the bigger/more pump/s) However as the temps drop below 15 below the cold from those windows becomes noticeable.. that's when the forced air furnace is kicked on. Since the ducts are right below the major glass areas there is a great deal of added comfort in those areas only and only at those temps..
Compared to similar sized nearby homes My energy use is a fraction of my neigbors. Approx. 1/3 (oh and I walk arounfd bare foot all winter)<grin)
As for using cork on your floor,, true enough that will certainly reduce one of the objections that I have to concrete. However, two more points
Cork is not terribly durable.. Well not as durable as hardwood is.
Second cork is a good thermal insulator.. reducing the heat transfered from the in-floor radiant. It seems to me you're adding a great deal of expense to arrive at about the same spot that a staple up system does.. IMHO
The underfloor option is less effective (therefore making your heating system less efficient), requires greater attention to detail and additional material, than does the imbedded option. Other than that, there is no difference. I have experience with both. I designed, sold, installed and problem solved hydronic systems for years. I was the local Wirsbo rep in my area.
Between the joist (BTJ) systems are less effective because to get the heat where it is desired, you have to pass through the sub-floor and the floor covering. The aluminum plates helps to transfer the heat to the underneath side of the sub-floor. Higher water supply temperatures are required to provide the same heat flux (you're an ME, you know what that means, right). Depending on the boiler you have or plan to use, this could/will affect the thermal efficiency of the unit. Lower temperatures, especially in high efficiency, condensing boilers, means higher efficiency. To help keep the BTJ system more effective, you have to seal/insulate the space between the joists, else a fair portion of the heat you wish to provide to the floor above is conducted, convected and radiated elsewhere.
The manner in which you imbed tubes in the floor (TIF), be it in a WarmFloor type of product, a QwikTrak or similar panel with space for tubing, or in a substrate like lightweight concrete, gypcrete, ThermaFloor or the like, is arguabley important, but no matter which method you employ, the TIF installation is more effective and requires less material and labor to install (i.e. no critical requirement to insulate BTJ).
Uphonor/Wirsbo products are adquate, not the best. I prefer Rehau. I sold and used both. Rehau is superior.
if you are comparing Quik Trak with Joist Trak, Joist Trak is a more effective product.Even though it is in the joists, it has superior conduction to quik trak by a fairly wide margin.Quik Trak's conduction path, even though it is on top of the subfloor, is still extremely weak, and still has to traverse 1/2" of plywood, compared to an increase of only 1/4" with a typical subfloor to go into the joist.. only a small stripe at the pipe itself has direct conduction to the floor. Joist trak has a real groove, real aluminum, with real contact area to the subfloor.Wirsbo's own output charts corroborate this, as does our experience in the field.There are better overfloor panels, like Raupanel. Raupanel is also about $3 to $4/sq ft more expensive than heavy plates in a jost bay. You'll probably drop 15 to 20 degrees from your operating temperatures in many cases, but that's still a pretty bitter pill to swallow and if the poster can't afford Warmboard, he can't afford Raupanel either.Quik Trak in particular, IMHO, is pretty much a waste of money unless you HAVE to be on top of the subfloor and you HAVE to have a 1/2" profile. I would use heavy plates in the joist every single time instead of it.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Rob,
You work with this everyday and I trust your knowledge on this. It has been several years since I was directly involved with infloor heating projects as a designer/supplier. I prefer imbedded designs, and I prefer Rehau over Wirsbo/Uponor. I have no direct experience with Warmboard. 90% of the my jobs were concrete slabs. I did a RauPanel job that was very successful. Never sold any QuikTrak. I never installed a between the joists system, but did design a few. I don't prefer that way of heating, regardless of the brands or products involved.
slabs are definitely great. Warmboard and raupanel are very effective products as well. but short of those options, heavy plates in joists do a pretty darn good job, better than the vast majority of other over-floor panel products out there, and WAY better than light plate or plateless joist systems for sure.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Rob, I see the term "efficient" thrown around loosely in connection with "radiant" floor heating. What is meant by that, most of the time? Is it referring to getting out the required heat in minimum feet of PEX, or minimum lag time to warm up things? I can't imagine it's referring to fraction of the heat source that goes into heating the house, because all of the heat (except for what goes out the vent pipe) goes into the house, as with any heating system.
frankly it's misused, an awful lot. people imply your fuel bills will be lower and that can be true, but it's a complex interaction of factors there.but using lower temperature water to heat can increase overall system efficiency for a variety of reasons; generally things like lower parasitic losses, lower exhaust temps, stuff like that.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
NRTRob,
Thanks for your input. Based on your statements, I'm going to focus on below-the-subfloor systems. I agree with your summary of the Quick Trak product, from my engineering point of view.
I can afford to use any product, but I don't want to spend more than needed to have a very good system, based on cost/benefit and value for my money. I'm also leaning toward the below floor systems because I won't have to adjust anything for the increased floor thickness.
I just finished reading ASHRAE's paper "Radiant Floor heating in Theory and Practice", and I liked what they found about using under floor heavy plates together with Styrofoam spaced 5/8" below the panel.
I'm thinking that I'll place insulation above the unheated spaces (garage below 1st floor living space), but leave it out on the second floor. My logic is that I'll get some radiant heating from the ceiling to assist the first floor heating. The second floor will be warmer anyway because warm air will rise through my large stairway space, so the second floor will need less heat flux, and can afford to give up some of it's heat.
I also need to select the manufacturers of my components. Another post on heatinghelp.com suggested that Thermofin C is a better product than Quick Trak, with respect to fitting the PEX more tightly. Do you have a preference?
I've also read (on your website) that you use Mr. Pex brand tubing. One thing I like about the Wisbro Pex is the ability to expand the PEX tubing and slip it directly over a barb fitting of similar material, whereby no compression clamp is needed. This seems to make more sense than putting pex over any type of metal fitting that will have a different coefficient of thermal expansion, and especially where a compression ring affords more opportunity for a failure. Can this be done with Mr. Pex tubing? What do you think?
By the way, you need to fix the main page of your website - today it is not working. I was able to go directly to the products page via Google, however.
Thanks,
Paul Formisano
do not skip insulation under a joist system.I will repeat that.Do not skip insulation under a joist system.stratification is less with radiant: downward loss can be severe: you cannot shut it off from the first floor if it overheats (and it can); you are unnecessarily raising your water temperature requirements on the 2nd floor making it work that much harder than it needs to.We use radiant engineering's thinfin "C". it's a better plate than joist trak, but they will both perform well.any PEX-A product has expansion memory. I would not personally choose to buy a limited use proprietary tool when a compression fitting would do instead, however.the page is slow to load sometimes, but it seems to be working for me? I'll check into it though, thanks.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Good points. I agree. I'm so used to living with hot air systems all my life that I forgot about the drastically reduced stratification of a radiant system.
Thanks,
Paul
One thing I like about the Wisbro Pex is the ability to expand the PEX tubing and slip it directly over a barb fitting of similar material, whereby no compression clamp is needed. This seems to make more sense than putting pex over any type of metal fitting that will have a different coefficient of thermal expansion, and especially where a compression ring affords more opportunity for a failure
You can buy a Wirsbo expansion tool on e-bay for about $175 any day of the week, and sell it for the same price when you are done with it.
The Wirsbo system uses the cheapest, most practical, easiest to install, and most trouble free connections available (pro pex expansion rings)
A Propex ring costs about 20 cents....your typical compression fitting costs about $5.00 or so...sometimes much more. It doesn't take long to pay for your tool investment!
Their brass fittings are also very reasonably priced and versatile.
We install over 100,000 feet of Wirsbo pex every year and I cannot remember ever having a failure or leak at a connection.
See the new rings yet? They have a ridge to help stop them from slipping.
The new valve/wallplate combo is interesting.
Rich.......Yes, I 've seen the new rings and am looking forward to using them. We have to go through a few thousand more of the original style first!
That is a big improvement because it not only makes it easier to slide the ring on to the pipe, but stops it in the right place too and locks it from sliding back.
( I'm sure you know that, but I just wanted to mention to others that it is a good improvement to a good system)
As far as I know, they are only available in 1/2" now.
As for the proPanels.....slick, but possibly a little pricey??
QuickTrac will be more responsive and efficient. But that has been said.
As for expense, take note of how much, if any, insulation you'll need to do under the subfloor.
I've done both, and when using underdeck components (JoistTrack w/ tubing), you need to spend $ on L & M to effectively insulate and seal the cavities of the joist bays, so as to contain the heat and get max transfer up through the deck to the flooring above.
Using above-the-deck QuickTrac panels, we've not insulated below, but that may not be best practice.
Can someone chime in here and tell us what is the Uponor best-practice recommendation for doing insulation below, when using QuickTrac panels?
I's a structural engineer, not an ME like you, and didn't get the solid grasp of thermodynamics as you did. In fact, I darn near flunked thermo.
View Image
"A stripe is just as real as a dadgummed flower."
Gene Davis 1920-1985
From "Modern Hydronic Heating" by John Siegenthaler. (Good book by the way). Insulation should be installed in the joist bays to minimize downward heat loss. How much depends on the temperature of the space beneath the floor as well as the R-value of the floor coverings. A conservative rule of thumb is to provide a minimum of ten times the finish flooring R-value as underside insulation. Insuation is essential for proper performance. Some suggested minimum R-values:
Floors over heated space: R-11
Floors over partially heated basement: R-19
Floors over vented crawlspace or exposed to other ambient conditions: R-30
The book gives the same suggested R-values for each type of radiant installation: gyp., underfloor, and above floor.
Edited 6/4/2008 4:04 pm ET by Doobz26
Edited 6/4/2008 4:04 pm ET by Doobz26
Gene,
From a heat transfer standpoint, it is important to insulate heated space from unheated space to save energy. Eventually, through conduction, a subfloor will become nearly the same temperature as the floor above it, and will lose energy to unheated space below. The rate of loss below is less than the rate of loss from above because warm air rises and cold air sinks, so the temperature difference is less under the floor than above it (during heatup), but you will still lose energy and should insulate - unless you want to heat a finished basement.
I aced Thermodynamics, took three years of it plus two of heat transfer. Truth be told, radiant flooring transfers more energy in the convective mode than the radiant mode. True radiant heat transfer is generally ignored by engineers for low temperature systems in the range that we live in. I'm not sure why or how the term "Radiant heat" got started for these types of systems.
I took a look at the Raupanel product. It looks almost as good as the Warmboard. I'm going to check the price.
Paul
Did you find a price on the Raupanel? I'd be curious as to how that compares to the quicktrack.
Again, Quik trak will NOT be more responsive, and it will NOT be more efficient than a heavy plate joist system. If that is an experience you have, it is a control or flooring issue, not a panel type issue.All radiant floors should be insulated underneath. to what degree depends on your method, and what you are doing below the radiant panel.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I'm glad to know that, Rob. I stand corrected. One of our pro heating contractors here promotes the QT as a faster warmup and better efficiency.
For JT installations in a deck with heated living space below, what is your recommended insulation scheme for the between-joist cavities?
View Image
"A stripe is just as real as a dadgummed flower."
Gene Davis 1920-1985
I should eat a few words first. response time might be fairly similar (that's not a characteristic our systems worry about at all typically, so I haven't paid attention to that in the field), might even be slightly in quik traks favor, but efficiency is definitely not better. heavy plates drop 10 to 15 degrees in water temperature requirements, if the joist bay is properly insulated.I would want at least R13 over a heated living space, under a plated joist system.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
To save yourself money you can fabricate your own above the floor system, known as the sandwich method. Labor intensive but alot cheaper than a warmboard.
FCOH,
Did you make up a special sheet metal rolling fixture to create the aluminum channels? I was thinking about doing that because I made a custom tube bending jig before that worked perfectly and I figured I could do the same with sheet stock.
Thanks,
Paul
If you put it above the floor your going to be tripping on it all the time. I'd put it below. Not an engeneer.
Above the subfloor and below the finished floor, in between, vs. below the subfloor are the options.
I did my new house above floor. But I made my own quicktrack using 3/4" plywood and a radius template for the switchbacks. I cut everything at e.g. 10 deg angle and about 8" wide ... My wife and I laid the tubing and screwed the plywood to the floor as we went. It's labor intensive, but it worked well. Can use e.g. a chisel to wedge the plywood tight against the tubing/previous plywood row.
I was lucky to buy 1600 sqft of used plywood in good condition and also some square drive screws. I bought some preformed aluminum sheets like 8" x 24" and interspersed those in the straightaways.
A lot of extra work working around special areas ... doors, corners, etc., but it really worked like a charm and I was very happy with the way it came out. LOTS cheaper, but more labor ... pay your money take your choice.