sawoodham
New Member
Posts:1
 |
| 18 Apr 2012 12:10 PM |
|
Wise Ones,
Posting newbie, but i need help. Our old home (circa 1930) was fitted with radiant heat under the wooden floors. It doesn't work well because the tubing is under the subfloor, and though the previous owners insulated just heating through the subfloor and surface floor seems to be too much for it. it is also undermined by all the old windows and the fact that part of the 1st floor was unrenovated and unheated. we hope that by replacing all our single pane windows, we'll get the heating situation to an acceptable, if not most efficient level.
We are undertaking our own renovation, and would love to have radiant heat, as we love it in principle. Problem: half the 1st floor flooring will be new and that is where we thought we could install radiant heat properly with the right type of subfloor with trenches (as i understand it) for the tubing. however i understand that the floor heights between new and existing will differ and we don't want that either.
is warm board or something else and option for what we can do the to-be-renovated areas and the to-be-left-alone areas that could work to effectively heat our home. Or do we have to take up the entire surface floor and deal with everything, or just go FHA as our contractor prospects seem to be encouraging us to do???
thanks!
sara
|
|
|
|
|
|
|
NRT.Rob
Veteran Member
Posts:1741
|
| 18 Apr 2012 01:37 PM |
|
joist mounted radiant can work well if it's got a same amount of wood on top, and you're using heavy plates. chances are you need to improve your envelope and maybe your joist system is not using good plates?
A heat load calculation answers these questions. it's possible Warmboard would do the job where joist plates wouldn't.. but that's just guessing and doesn't address the existing areas.
what kind of water temps is the system running? what's the heat source? |
|
| Rockport Mechanical<br>RockportMechanical.com |
|
|
BadgerBoilerMN
Veteran Member
Posts:2010
|
| 22 May 2012 08:43 AM |
|
We specialize in radiant floor heating retrofits here in Minneapolis. Your problem is not uncommon and we often use more than one product in the same space i.e. sub-floor plates and grooved panels (Warmboard is primarily use for new construction) to make warm floors and keep them level at the same time.
As Rob points out, only a proper heat load will give you a clue. |
|
| MA<br>www.badgerboilerservice.com |
|
|
MikeSolar
Basic Member
Posts:376
|
| 22 May 2012 10:40 AM |
|
Do you wish to keep the rest of the floors (nice hardwood or tile)? If not, many times I have put sleepers on the sides of the joists and plywood between the joists so that I could get an extra 3/4" for 1.5' of light weight cement. It takes a bit of labour but the result is well worth it. Low water temps, good efficiency and you can put whatever you want over top.
Although I have done "stapleup" in the 90s (too many times), I won't do it now. Efficiency means low water temps and that mean thermal mass and tight tube spacing (6" max). Tight spacing is not as necessary with a boiler as with a heat pump but it still helps. |
|
| www.BossSolar.com |
|
|
BadgerBoilerMN
Veteran Member
Posts:2010
|
| 22 May 2012 06:32 PM |
|
Seriously?
We use extruded aluminum plates below existing floors (if the heat loads permit) and get predictable results. I have no idea why you would use cement between joists for any purpose, though I admit it sounds like a lot of work. |
|
| MA<br>www.badgerboilerservice.com |
|
|
NRT.Rob
Veteran Member
Posts:1741
|
| 22 May 2012 07:17 PM |
|
that's a "ledger" method a few of the internet companies promote. at least he's using concrete and not the crappy sand bed those companies advocate. heavy plates would of course be a lot easier, and they didn't really exist in the 90's. the loads of course always determine what is best.
thermal mass has nothing to do with water temps though. |
|
| Rockport Mechanical<br>RockportMechanical.com |
|
|
MikeSolar
Basic Member
Posts:376
|
| 22 May 2012 08:11 PM |
|
It has worked very well when people have had height issues. There are 1000s of old houses around me where the bathrooms and kitchens use a ledger method with 3" of cement below the tiles. The stuff hasn't cracked 100 years.
Not going to argue about thermal mass and water temps. I'm too old school or maybe "European" in my thinking to use aluminum plates anyway.
|
|
| www.BossSolar.com |
|
|
BadgerBoilerMN
Veteran Member
Posts:2010
|
| 22 May 2012 09:25 PM |
|
We have a couple of old houses in Minneapolis/St.Paul and we put tube in a mud-set when it makes sense, but I drive cars, use power tools and were bright clothes on occasion, so aluminum plates go under my retrofit floors. I am glad no one tries to openly defend bear-tube staple-up any longer.
|
|
| MA<br>www.badgerboilerservice.com |
|
|
NRT.Rob
Veteran Member
Posts:1741
|
| 23 May 2012 10:23 AM |
|
not to be rude Mike, but the word is "incorrect", not "european" or "old school". thermal mass has absolutely nothing to do with water temps. it's conductivity that determines the temperature delta you need water to room to drive heat from one to the other.... that's it. thermal mass stores heat. it does not improve conduction. concrete has less conductivity than aluminum.
GOOD aluminum plates... and that's the key, you need good conduction pipe to plate... will outperform concrete with identical floor assemblies above every time. Of course, the floor assembly is NOT equal in the situation you're talking about. the concrete will perform better. but how much? is it worth the work? that's a very fluid question. in MANY... though not all... cases, the answer is probably not. |
|
| Rockport Mechanical<br>RockportMechanical.com |
|
|
BadgerBoilerMN
Veteran Member
Posts:2010
|
| 23 May 2012 10:37 AM |
|
Rob is right. This is why we use dedicated software to design radiant floor heating systems for new houses and renovations. We don't have to guess about the performance of our radiant floors.
Where we consult on older homes, many on the Historic Register, we make the radiant panels work using the most cost effective techniques available. We would never use the "Ledger" method unless an architecturally important feature of an older home required it.
We have a lot of PEX in slab-on-grade concrete, but for "dry" radiant floors, it is usually an extruded aluminum emitter or an grooved aluminum clad panel "sandwiched" between sub-floor and finished.
|
|
| MA<br>www.badgerboilerservice.com |
|
|
knotET
New Member
Posts:89
|
| 23 May 2012 10:06 PM |
|
Rob: thanx and most all.
Thanx..
2x Heat capacity (mass here) to 1x just takes twice as long to get toesies warm if conducting Ex at a same rate of conductivity at a same surface temp considered only if a same TOP SURFACE (equal) flooring material is touching those toes...
I.E.
A ceramic heater or a hair-dryer blasting on a ceramic coffee mug... Both can be equal in Ex transfer after the plugs are pulled at the same time. 2 mugs in the heat of the dryer just took 2X Time to get to a peak temp, and 2 X longer to cool off when unplugged. Rob, thanx again. |
|
|
|
|
knotET
New Member
Posts:89
|
| 27 May 2012 02:15 AM |
|
some interest to me:
'studies to do' catagory
http://www.ohio.edu/mechanical/thermo/Applied/Chapt.7_11/CO2/CO2geotherm.html |
|
|
|
|
MikeSolar
Basic Member
Posts:376
|
| 27 May 2012 07:52 AM |
|
Posted By NRT.Rob on 23 May 2012 10:23 AM
not to be rude Mike, but the word is "incorrect", not "european" or "old school". thermal mass has absolutely nothing to do with water temps. it's conductivity that determines the temperature delta you need water to room to drive heat from one to the other.... that's it. thermal mass stores heat. it does not improve conduction. concrete has less conductivity than aluminum.
GOOD aluminum plates... and that's the key, you need good conduction pipe to plate... will outperform concrete with identical floor assemblies above every time. Of course, the floor assembly is NOT equal in the situation you're talking about. the concrete will perform better. but how much? is it worth the work? that's a very fluid question. in MANY... though not all... cases, the answer is probably not.
If it is incorrect, then a market with 500,000,000 people, and the research institutes that the market pays for are wrong too? Aluminum plates are virtually unheard of in europe. They are for our construction methods where weight may be an issue and the impatience of builders to let gypsum dry properly. In my opinion, if you want LOOOONG term quality, comfort and reliability, the tube goes in a thermal mass. In the end we are looking for two things from a heating system, comfort and economy. Comfort can come in many forms and Dana1 is making some convincing arguments for ductless splits (much to my chagrin), but a radiant, even if you cannot tell it is on, is still the best in my opinion. There is no way with a aluminum system that you will cover 100% of the floor area and since heat distributed is based on radiation area, tube in cement or gypsum (and I accept the fact that aluminum is a better heat conductor than cement, I would be a fool not to) is still a better overall distribution method. You must make up for the areas where you cannot have tubing and aluminum and that means a bit higher liquid temps, whereas in cement, the heat will slowly migrate and stay in cement that does not have tubing (better than it will in a insulating wood covering.) In our low mass houses, the ability to change temps quickly is way more important than in a high mass home which won't change due to outside influences as quickly so I accept that the system has its place, especially in dual system houses (forced air and radiant in the same area) In the end, to me, comfort is not in quickly changing temps, it is about keeping whatever comes in or goes out to a slow trickle and I will notice changes in room temps much more in an aluminum system than in a cement system. I am looking for my old design manuals from Rehau and wirsbo that have some more info to support my claims (way too much stuff in the shop). |
|
| www.BossSolar.com |
|
|
knotET
New Member
Posts:89
|
| 27 May 2012 09:54 AM |
|
Posted By MikeSolar on 22 May 2012 10:40 AM
... Low water temps, good efficiency ...
[the accuracy of Mike's remark is in a few ways possible: At a SOURCE desired to be receiving all the same (compared to other under-floor designs at a same total volume of distributed fluid flow) in-cement-radiant systems of known fluid flows measured/adjusted per BTUh Ex ([Q]-work- of an Energy-eXchange) -all at a same condition- but at a lower temperature EW/EL returning to a heating source, i.e.) in solar collectors (as [W]-heat exchange HX devices) and hi-eff boilers that with nGas may need a low-er enough temp for to condense, and also about using lower temp EL say to an HX in HW-AHP and -GTHP, at their condensers in refrig heating, (industry-known) -- these then lower temperature flows getting back to the source(s) like those cause for a solar system to allow that SAME Ex to be produced in less sunlight, the nGas burner shuts off sooner, the compressor >than the heat sink radiating Ex conducted to it as a zone, results in less amps and/or a HtP cycles more into lower staging/etc. (IF, then) liquids receive a requied SAME Ex while distributed to MORE SURFACE AREA (large enough cement floor receiving), - but just in less time at a particular SOURCE of of the same work::: -Then too, if Ex at the 'heat-sink' in- a top layer of a floor-radiation as a 'distributor' , HX does not look like jacob's ladder in an infra-red photo+AND the MEAN-to-average-temp.diff (dT) for over/across EVERY sq-inch of that HX-floor is found sufficiently meeting a load as would a plate and/or tube system yielding "strips" of a same heat Ex but there required with hotter radiant system fluids, - less efficiently delivered at a same flow from a same distributed load back at HIGHER EW to a temperature-differentially sensitive source.]
---
... and you can put whatever you want over top. [from his other posts, I bet he does not mean 1" insulation padding]
Although I have done "stapleup" in the 90s (too many times), I won't do it now. Efficiency means low water temps and that mean thermal mass and tight tube spacing (6" max). Tight spacing is not as necessary with a boiler as with a heat pump ---- but it still helps. [ it surely do, bro.!] |
|
|
|
|
knotET
New Member
Posts:89
|
| 27 May 2012 09:59 AM |
|
Posted By NRT.Rob on 18 Apr 2012 01:37 PM
[Is it for sure already] "not using good plates? "
SAW: any more 'room for a view' ?
A heat load calculation answers these questions. it's possible Warmboard would do the job where joist plates wouldn't.. but that's just guessing and doesn't address the existing areas.
what kind of water temps is the system running? what's the heat source? |
|
|
|
|
jonr
Senior Member
Posts:5341
|
| 27 May 2012 11:01 AM |
|
Having gone through the calculations awhile back, I have a lot more respect for aluminum plates and less for concrete. And that's not including the drawbacks of high mass radiators.
As an aside, I'd take thinner aluminum plates with more coverage area over thicker ones but less coverage. Of course thick plates with 100% coverage would be ideal (but expensive). |
|
|
|
|
MikeSolar
Basic Member
Posts:376
|
| 27 May 2012 02:41 PM |
|
Posted By jonr on 27 May 2012 11:01 AM
Having gone through the calculations awhile back, I have a lot more respect for aluminum plates and less for concrete. And that's not including the drawbacks of high mass radiators.
As an aside, I'd take thinner aluminum plates with more coverage area over thicker ones but less coverage. Of course thick plates with 100% coverage would be ideal (but expensive).
The thickness of the plates, and tube spacing, is really a function of the time needed to dissipate the heat from the tube. Even in solar panels we have found that we don't need more than .8mm thickness to get the heat from the perimeter of the fin to the centre where the heat can be removed. The same is true of aluminum for transferring the heat to the floor. I think the only reason some companies (Rehau for one) use thicker aluminum is that they have an extruded product and there is a minimum thickness needed for the process. They also want more structure for strength but don't need it for heat transfer. The drawbacks to high mass rads are placement and aesthetics (there is no accounting for personal taste), and the minimum water temps needed to run them. Temps are a function of heat loss of the building so it is entirely within the designers ability to ensure it is suitable for low temps. What other drawbacks do you see with rads? |
|
| www.BossSolar.com |
|
|
MikeSolar
Basic Member
Posts:376
|
| 27 May 2012 02:44 PM |
|
Posted By knotET on 27 May 2012 09:59 AM
Posted By NRT.Rob on 18 Apr 2012 01:37 PM
[Is it for sure already] "not using good plates? "
SAW: any more 'room for a view' ?
A heat load calculation answers these questions. it's possible Warmboard would do the job where joist plates wouldn't.. but that's just guessing and doesn't address the existing areas.
what kind of water temps is the system running? what's the heat source?
I won't use joist plates anymore. Too much wood insulation. Besides, I don't think you can get the 50-60 years out of a tube that is "potentially" under the stresses associated with expansion in aluminum. There is a place for warmboard but it limits layout design somewhat. |
|
| www.BossSolar.com |
|
|
Blueridgecompany.com
Advanced Member
Posts:656
|
| 27 May 2012 03:38 PM |
|
Hello All,
well I have to chime in here, we have been supplying a surface mount sandwich system for some time now RHT Floor panel coupled with the thin omega style heat plates. Unlike a staple up systems, surface mount floor panels respond quickly and work well at low temperatures, maximizing the use of condensing boilers, geo thermal or solar. In a building where light weight cement is impractical due to weight or extensive finished wood floors where you will be nailing your floor the floor panel surface mount approach is a good alternative to the staple up with plates. As you all know,The staple up requires a higher delivered water temp due to the push through the additional sub floor, there goes some efficiency and here comes expansion and contraction.
As to the extruded aluminum, not convinced it makes a difference on operation cost to justify the added product cost in an already stressed economy. We see a lot of DYI and the reason for that is to save where you can.
Spend the extra on a condensing boiler, insulation,energy star appliances.
Dan |
|
| Dan <br>BlueRidgeCompany.com |
|
|
NRT.Rob
Veteran Member
Posts:1741
|
| 28 May 2012 04:30 PM |
|
Extruded plates will beat the pants off of nearly any lightweight plate out there... no lightweight can do a tubing groove with as good of a contact. it's as big of a difference as no plates vs lightweight plates again.
Warmboard aluminum will outperform concrete as well with identical flooring assemblies above... it's near 100% coverage and on top, no extra insulation. I bet with the labor savings it's probably similar in cost too, and faster response. I'm not saying concrete is BAD, I'm just saying, it's hardly the only game in town and you're jumping through some pretty silly hoops to make it work on what is at least partially superstition based on your responses. If you're doing a slab on grade home, obviously put it in concrete. If you need some weird custom framing detail, maybe not.
extruded plates also hold pipe so it can't move, so the "thermal stresses" are moot. no argument that plates in a joist bay won't be as good as concrete on top of a subfloor, of course. but I design very little but very low temperature systems, and we use both plateless and plated radiant on a regular basis when it makes sense to do so. which is a lot of the time, when you run the numbers. I have at least a couple dozen plateless systems out there at 110-115 degree design temps because the loads allowed for it. My shop, on the other hand, is 90 degree max warmboard with wood on top.
|
|
| Rockport Mechanical<br>RockportMechanical.com |
|
|