have pretty much finished the exterior of an addition inc. a big deck and am now going through plumbing, electrical & heating
theirs is forced air gas but to get a duct to the main area of the addition I will have to cut a swath of hardwood & subfloor with a potential of encountering dirt almost to bottom of floorjoists – not too bad but the old 8″ thick foundation before getting to new crawlspace will not be fun either – this transition area built in 1913 between an open basement & the addition i’m bldg w / crawlspace is about 11 feet
they are not looking forward to this ( nor am i ) and asked me about alternatives
they do not want to consider baseboards or wall heaters but asked about heating under the floors & electrical
I told them of the endless nails we will be driving through the red oak probably eliminates the possibility of electric radiant heat but what about under subfloor radiant heat using their gas water heater, pex & heatshields/max insulation ?
the addition of a boiler or the like would put us back in the excavation category I think but a tankless might keep us in ballpark
this is a conditioned space w/ heat registers now about 22 feet from outside perimeter walls
2 X 8 floor joists 16″ centers 3/4″ t&g subfloor 18plus ” crawlspace
I do know that this is not optimum flooring for radiant situation but it is what we have
all ideas & experiences appreciated
Replies
that's basically how my whole house is heated.. there is a slight loss of effeciency due to the R value of the wood involved but if once you install it, you insulate each joist bay withfoil back foam insulation the loss is extremely trivial.
Radiantec can seel you everything you'll need. They are a regular advertizer in Fine Home building magazine. You can trust them completely..
so Frenchy your only heating source is gas water heater?
and the setting is 115 - 120 degrees?
No. Two electric water heaters are my primary heat source, however on really cold days (-20 or below) I supliment the heat with gas forced air with the ducts aimed at the windows.
Don't forget my walls are 18 inches thick.
I usually don't need the 2nd water heater untill the temps are well below zero. I have a valve that I need to go down and turn to convert the second from hot water to both hot water and and heat..
Not an easy one for sure.
How big is the area we are discussing?
Staple up with REAL extruded alum plates at this stage seem your best bet. Forget about the tin foil and reflective insulation (dust will do that in in short order)
Keep your tube spacing down and push whatever insul up tight.
Put in flooring and grind off the nails ,ouch.
Oooh tankless, Siegenthaler probably not like.( Very high head loss and not rated for this use), some tanks rated for heating, worth a look.
Hate to disagree with Frenchy (but most everyone else does soooo. :) ) Do your research and if necessary hire a real pro. Don't want to go dissing any internet retailers now do I?
I'll definitely be talking w/ some local heating pros but it always amazes me how behind we are here concerning new technologies that workthe area is 24' X 12" and transition area ( where ducting space would have to be provided for ) is 12' X 12'
now for my appreciation for effective systems just the fact theirs is gas this scenario may be better than yours - they do not have 18" walls
On the other hand you aren't trying to heat 5500 sq. ft. where temps get down to minus 40 below. It's a matter of heat loss calculations, something that Radiantec helps you acheive.
It's absolutely true that you can turn it over to experts who have their own bias. That's the easiest way and all you have to do is write a check..
On the other hand those so called Pros use simple rules of thumb with a nice broad safety margin built in. Then they convert everything to materials they have available. That's where effeciencies go down the drain. You may be buying a lot more heat than needed or paying for a much bigger system than is really called for..
If I'd listened to the local HVAC guys my system would have cost me $15,000 more than I spent plus my heating bills would have been significantly higher than they are.
Just to show you the degree they over spec things.. the smallest furnace I was recommended in my old house was 165,000 BTU virtually everyone else speced a larger one. Yet during the dead of the winter when all I had on one wall was a blue tarp that furnace kept me plenty warm and comfortable even with 40 below wind chills..
Oh. Forgot one thing. Open/combination systems are verboten with the real pros.
Can you say, Legionnaires disease? One system for heat, one for potable, flat plate heat exchangers are good!!. Would you really want to risk your client's health and lives?
I appreciate your feedback
not sure this will enter inspection / code phase unless asked whether there was a heat source providedam here to learn all I can
would putting a pump on it & the fact it would not be a very long trail of pipe / tube limit that legionaire quotient
Unequivocally no to any and all open/combination heating systems. No exceptions, no buts ,no nothing, not at all , not ever. Can your say possible stagnation in the non-heating seasons. It is just not worth the potential risk of your client's aspirating legionnaires whilst in the shower. Try Google Dave Yates and Legionnaires.
Sorry. :) Did I say never?
Tell us how you really feel. :)
The open system Radiantec sells doesn't cause stagnation, no more than any other waterline. Or a hot water heater. And it's OK in the IBC. California's plumber union says PEX is poison, too.
No, it probably wouldn't. You need to separate potable from the heating side, I think. Either a separate water heater or a heat exchanger. The code is your friend here, shouldn't take it as an option ... that's why they call them "life safety" codes.
Why is it you can't go through the rim joist w/ a duct? Also, assuming your new addition is energy efficient, you may not have to run ducts to the exterior wall (depending how far it is). I was a little confused by your statement that it was 22ft to the register. Remember, if you'd eliminated an exterior wall w/ an addition, your heat loss to that adjoining room is reduced (or eliminated).
If considering radiant floor, focus on the heat source options. Tankless, small tank, regular tank, electric, gas.
Where is the current furnace? Closet? Where is the existing ductwork if the joists are almost on the ground already?
My other question would be why do you wait until the framing is done to consider heating options? Seems like this should have been 'worked out' during the design/planning phase. No offense intended ... I've no idea what the details of your project are ... and ultimately stuff does happen.
You'd run it through a heat exchanger, I believe ... not use it directly.
a little knowledge is a dangerous thing.
For example legionnaires disease is a airborne spread pathogen.
Second there are far more likely scenario's whereby people get sick from water.. most likely is contamination at the source.. most cities have open source water supplies. Lakes, rivers, ponds, etc.. that happens far more often than legionnaires disease..
Next is poor maintenance of in house filtering systems. In my own case I found a hidden filter than had never been serviced in the 15 years I'd lived there prior to teardown (I didn't know it was there) Since the house had stood vacant for over a year and before that had been occupied by a young kid for 3 years there is every likelihood that filter was nearer to 20 years old. (no, we never got sick from the water)
Followed closely behind unused bathrooms etc.. One bathroom in the old house was virtually unused for nearly a decade. I'd go in there and check periodically and have to turn the water back on to refill the toilet bowl because the water had evaporated out of the tank and was allowing sewer gas to escape.
That whole bathroom was on the end of a separate run so it was a real potential source of contamination..
Finally cabins or vacation homes and other locations where the water is dormant for the 8-9 months they are not in use..
As you can see normal life continues on in spite of stagnant water systems.. Which is why the requirement for open/closed water systems is a local issue not a national issue.. Some communities allow it and some don't.
You are right. a little knowledge is dangerous.
Legionaires breeds in water. Then it is released into the air through a shower head. Hmmmmmm.....................
You choose to ignore the most common cause of water born disease and go for the really obscure. Far more people die from water borne contaminates at the source than have ever been affected by legionnaires disease.
It's a unique set of circumstances needed to create the breeding grounds for legionnaires. The incident which caused the first detected case of legionnaires to break out was the air conditioner hadn't been serviced in several years. There was open stagnant water which breed the disease and then it was drawn in thru the air intake
eliminate any of those conditions and it's not possible..
You are correct about a little knowledge being a dangerous thing.
Legionnaires is water borne in the air we breathe by aerosolized droplets of water. This disease affects the old, sick and weak and is thought to be extremely underdiagnosed or just misdiagnosed as plain old pneumonia.
"open stagnant water which breed the disease and then it was drawn in thru the air intake "
Sounds like a shower connected to an open system to me.
Why take the risk?
How many people were killed last year on the highways compared to how many were run over and killed by zebras?
A cogent argument requires that we do not create straw men to question the validity of the main point.
Why take a risk that you obviously do not want to understand?
can you find a documented case? I hear this frequently but I'm still waiting.
Take thousands of feet of plastic pex tubing on manifolds in the typical system and the fact that bacteria multiplies beautifully on plastics in a nice warm wet environment and you have a disease amplifier bar none.
Legionnaires exists and has been shown to like these environments.
I only have to read as a layman and decide that the risks are not acceptable when there is a sound 100% safe alternative to an open system.
The more these systems proliferate the sooner you will have your proven documented case. As it is no one is really looking and cases may simply go misdiagnosed.
"bacteria multiplies beautifully on plastics"So plastic of any kind is unsuitable for potable water? You're right, why take the risk.
In a warm stagnant environment.
Edit: please use the entire quote to be fair.
Edited 12/1/2008 6:54 pm ET by s crough
Actually copper may be better as it has some antimicrobial properties.
But let's be serious most water is chorinated and renewed constantly through domestic potable piping.
Many thousands of feet of tubing unrefreshed can become stagnant
most water is chorinated and renewed constantly through domestic potable pipingTake a look at the Radiantec system, it's elegant. And refreshing!
Like I said earlier. I do not want to get into dissing an internet sales company.
Not all water is chlorinated and bacteria abounds in all untreated water sources.
I prefer the belt, braces and suspenders approach to my clients health.
The greatest advances in public health have been achieved through sanitation of the public water supply. Why compromise that phenomenal achievement to save a few bucks?
Last house I did was over 6000 feet of tubing on 4 manifolds. That is over a mile and definately not refreshing
So what time frame do you claim for stagnation.. if I leave a cottage for a week, a month, 9 months more? when should I call in the guys in white suits to allow me back into my vacation home.
What if I fail to use a circuit in the house say an unused bathroom for the same time? when should we move out?
The trouble with pros is that they became pros by doing something over and over again and being paid for it..
Monkey see monkey do sort of thinking is real common in construction..
It's hard to take what the guy who brought you into the industry and discard it because there are better ways of doing things..
If you've been doing something one way for your whole life and made a good living doing it, how quickly would you accept alternatives?
Because change involves an element of the unknown and the unknown reresents risk it's not only hard to do but your prudent nature avoids changes.. To your mind you are doing the right thing.. Let someone else take those risks..
I was in an excellant position to take those risks.. as the installer and maintinace guy I could quickly see flaws and where additional efforts/attention were required..
I came into it with a completely open mind.. In fact I didn't use the services of Radiantec. but in retro spect I sure wish I had.. they saved a lot of work for my brother-in-law and the system they designed works beautifully!
Any reason you cannot utilize a radiant ceiling? Works the same as the radiant floor, just not not under foot.
All the hubabaloo about mixed/open systems and Legionaires and other assorted issues, while all real concerns, do not apply unless you plan to combine you hot water comfort heat system DIRECTLY with your domestic hot water system. I didn't see any mention of this before the warnings were issued.
Using a tankless water heater will work, as will a water heater with a tank. IF your are going the least expensinve route (using a domestic water heater as a comfort heat source), I would recommend a small tank heater over a tankless unit.
I didn't see a mention of the size of the space, or the details of construction. In the PNW, the winters are relatively mild and water heaters usually have plenty of capacity for small additions.
Tim
I understand the concept of radiant heat however isn't that in conflict with heat rises theory?
Heat radiates in all directions. However objects further away "accept" less heat than nearby objects. So you would need more heat to do a floor from the ceiling than a floor from the floor wouldn't you?
So in your case, with radiant floors, is your head cold? :)
heat rises,
the peak of my ceiling 28 feet above my head is 1/2 degree cooler than my feet are..
No.
You are not paying attention here.
Heat radiates through space or conduction through materials.
Hot air rises. Through bouyancy and convection. And you have plenty :)
Your criticisms of other professions in your region may be warranted, but you hold onto some of the very preconceptions and misguided ideas they may have, and you need to cast your net farther to find better people..:)
I would have expected a little more stratification for a 28' ceiling.
In my old house I noted the ceiling was always warmer than the floor. In many homes that is the norm. I believe that indicates the flaws of typical heating/ insulation systems.
The fact that a digital infrared thermometer found only a total of 1/2 inch of temp drop in 28 feet means the insulation package and heat source is correct in my house.. I'm typing this in bare feet and it's 18 degrees outside right now.. The thermostat is set at 68 degrees. I can walk comfortably around the house and never feel the slightest chill. The fact that it's so much cheaper to heat than the old house 1/2 it's size with 3 times the number of windows.. is another bonus that I recieved from challenging the status quo.
I suspect your thermometer misleads you.
Hot air rises and somewhat stratifies, thus giving warmer temps up high rather than lower temps.
You must be moving that hot air somehow.
Hard to believe isn't it? Your experiance dictates otherwise doesn't it?
Well both my thermometer and far more crude attempts of measurement by my hands and feet confirm the same thing.. I can confirm it by focusing on spots every 2 feet or so and the temp drop is real and steady.. no stratification at any level.
Heat rises is how it's done.. right now the only heat source is in the basement.. there are no registers or ducts outside of the basement and since the second (or third) floor do not have any radiant heat in them (nor is the floor completely finished up there) the only heat they get is from what rises in the house.
But have you calibrated the instrument and are positive it is accurate?
Still hot air rises. Maybe you have a source of heat loss somewhere and do not know it ?
Could be misapplied efforts:)
Well I've confirmed the temp with several other sources and they all match. Water does boil at 212 and that's what my thermometer says...
Hmmm heat loss, I did tell you that the exact same furnace used to cost me $500 a month and now I spend $200 a month? This is in a house over twice as large with 79 windows.. No you didn't read that wrong 79 windows.. the largest are 3304 sq.inches the small one is only 240 sq.inches.
Bottom line I suspect there is little heat loss. Not sure knowledge yet. Gonna' wait until I do the full tighten up before I hire an infrared photographer.
Until I do I suspect that with a near 2/3rds reduction in heating costs in spite of doubling of size and tripling of windows plus added energy costs in intervening years. I'm not overly concerned.
OK. So the basement radiant and you heat the house. :)
Actually quite impressive when enough attention is given to details.
I ,also, am a fan of ICF and radiant, but I do weary of the gratuitous slagging off of professionals.
Just because your local experience is not great does not mean that some very talented people are not at work conceiving new technologies and applications. :)
I don't have a single problem with advanced thinking.. In fact I hunger for that sort of thing..
You are right though..
In the 17 1/2 years of selling equipment to the construction industry the percentage of people I've met who have been thinking, really thinking about things and how to improve them has been dismal.
If cars were built like the housing industry I know we'd start all our cars with hand cranks and still use wooden spoked wheels..
A digital infrared thermometer will only measure the temperature of objects, not air.
It does measure the tempurature of wooden beams or boiling water. The beams to get to those temps must be subjected to some way of transfering the heat into those temps. Air is the media or source for that heat transfer. ( the neat little red dot confirms that I'm hitting what I target)..
Don't you hate to constantly have to define every nuance of detail? I sure do..
I don't hate the nuances and the detail, but I'm an engineer, that kinda goes with the package. Some of those nuances are important. Water and wood count as "objects" in this case. I should have more correctly state that IR measurements apply to surfaces. This is such a case. Measuring the surface temperature of wood beams in the room may or may not be representative of the air temperature and stratification that exists. Here's why.
The beams, as we discussed in waaaaaay too much detail in another thread are wood and wood is not a very good insulator. Therefore, wood is a good conductor. The beam is in contact with something that may or may not be at the same temp as the air. The temperature is affected by heat conducted into and out of the wood more so by the contact and conduction than by the air.
The air in heated spaces is stratified unless a high volume of air movement is involved. This is just the physics of our atmosphere (another one of those nuances). Air at the same pressure, as it is inside a house, has different densities at different temperatures. The air closest to the floor is heated to the same temperature as the floor surface. The air above the heated air is cooler and more dense. The warmer air rises. This is a situation most are familiar with and results in stratification. The stratification in a space that is heated by a low temperature surface like a warm floor do startify much less than those that utilize higher temperature differences. This true whether forced air, steam or high temperature water is invloved.
If you wanted an accurate profile of the temperature stratification in you twenty-six foot high room, you would need to measure the air temperature with a scientific dry bulb thermometer, every foot or so. I wouldn't do this personally, because it is relatively useless information, but if need to prove the point, do it right.
Great explanation. I love and appreciate the details but wonder how many will.
one other point about wood.. it has mass.
Therefore it absorbs heat and is capable of radiating heat. when you have 50,000 + bd.ft. of hardwood you have a great deal of mass that is heated to the 68 degrees I set my thermostat at. As that mass cools it yield it's heat back into the room and thus stabilizes temp swings.. Since a significant portion of that mass is in the trusses I believe that is another reason why I have virtually no stratification..
(that and my 18 inch walls with an R30 rating, and my ceilings with an R 50 rating.) you take R 50 and cover every seam of the SIP's with 9 inches of white oak at a minimum (maximum of 18 inches)) you get pretty decent heat retention.
I don't know if you've seen my place you can if you want see it at 85891.1 & 94941.1 scroll through that thread and you'll see some of the timbers etc.. that stabilize the temp swings here.
I was presenting this only as an additional option to be considered.
Radiant heat transfer (between two "bodies" or surfaces) is directly proportional to the distance and the difference between the absolute temperatures ^4 (to the 4th power).
The "heat rises theory" (more accurately, warm air is less dense than cooler air at the same pressure, so warm air rises, heat does not) is mostly applicable to natural convection systems.
Floor radiant heat is closer to the occupants and transmits heat to the space by natural convection, so the same amount of comfort can be the result of a lower temperature difference. This would require lower supply water temperature and could possibly make the overall heat transfer more efficient. In reality, the differences are minor, other than the great feeling of warm floors to the touch of a socked or bare foot. The amount of heat transfered to the space and the occupants would remain unchanged, but it would occur at slightly different temperatures.
"Radiant heat transfer (between two "bodies" or surfaces) is directly proportional to the distance and the difference between the absolute temperatures ^4 (to the 4th power)."On the relation between radiant heat transferred vs. distance and temperature, I agree with the temperature relationship, but I have to question "proportional to distance." The heat absorbed is a matter of the relative areas of the emitting and receiving objects and the manner in which the heat spreads out as it travels from the emitter.
[Edit: make that area of the receiver relative to the area over which the emitted heat spreads at that distance]If the heat is transferred between two parallel surfaces (one hotter than the other), the distance won't matter if there is nothing in the way to absorb some of the heat. If the hot surface is linear (say, a hot vertical pipe in the center of the room), then the heat absorbed by something else would be inversely proportional to the distance. If the source is a point (eg. small sphere), then heat absorbed is inversely proportional to the square of the distance. [2nd edit: make that heat absorbed per unit area].Edited 12/1/2008 1:47 pm ET by DickRussell
Edited 12/1/2008 1:49 pm ET by DickRussell
In a vacuum, between two "black" bodies, etc., etc.
I recall the theory, and also the lab tests of that theory. Distance counts, but not much.
"Radiant" floor heating is a misnomer. I don't know who coined the term, but it has almost nothing to do with radiative heat transfer.
but it is pretty universally understood what's involved..
Care to explain?
BTW, "radiative" is not a word. Kinda make the rest of the argument a mute point, eh? But, I'll humor the post.
The heat transfer to people, objects and air in a space with a warmed floor as the "terminal unit" takes place like almost all heating processes in our atmosphere, by conduction, convection and radiation. Ulitmately, how much by which means depends on the circumstances. If you believe that radiant heat transfer does not provide a significant portion of the process, crunch the numbers to prove it to yourself. I did, because I once believed as you do. I was wrong, as are you.
Well, I was originally speaking relative to other, hotter heat sources, which radiate more due to a higher temperature difference with their surroundings. But I got curious and went over to engineeringtoolbox and found a useful table: http://www.engineeringtoolbox.com/radiation-constants-d_150.htmlHere are the radiative heat transfer amounts for small temperature differences between a wood floor and surroundings at approximately 70 F (530 F above absolute 0): 5 deg. F temperature difference (i.e. floor is 75F)((535**4) - (530**4))*.126*(10**-8)=3.8 btu per hour per sq ft10 F hotter:((540**4) - (530**4))*.126*(10**-8)=7.7
Look up the concept of mean radiant temperature. This is a critical factor in determining the actual radiant heat transfer in a space. 70 degrees for the surrounding space is not a good number, IMPO. 75 degrees is also a pretty cold floor as well. 7.7 btuh/sf will heat most well insulated spaces in mild weather. I have found in designing RFH systems with real wood floors in spaces with high heating requirements (over 35 btuh/sf) supplemental heat is required. The main reason is that to prevent damaging the wood flooring, a surface temperature of 85 degrees or less is recommended. For comfort to the touch, I have also found that temperatures up to 85 or even 90 degrees is about all you want to feel on bare feet anyways.
If you were to compare how much heat was transferred to the space via conduction and convection, under the same conditions as your examples, you will find them similar in orders of magnitude as the radiant portion of the heat transfer. The computations to determine this are more complex that simple radiation (have you ever heard of a Grashof number?) Which gets back to my point, that radiant floor heating actually does have plenty to do with "radiative" heat transfer.
In his first post he considers using the tankless without mentioning the need for a heat exchanger to isolate the heating side from the potable :)
My assumption was that the tankless WH would be used soley for the infloor comfort heating and not in addition to domestic hot water service.
I do not disagree that mixing potable systems with heating systems is an extremely bad idea.
You are correct. Initially he mentions using the gas hot water heater then goes on to mention tankless as an option.
My addition to that being whatever appliance is decided on be manuf. rated for that application.
Bad enough what we might do in our own homes but what we do for clients must meet a higher standard.