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Warm Air Rules...The reasons

Here in humid country, ya gotta have central air so 95% of the homes have forced air. I know from growing up in an old house with 6' radiators how comfortable it is. I also remember 3-4 window shakers to keep out the steamy stuff all summer. We have a few expensive homes going with RFH and ducts for cooling. But otherwise, we gotta do the best we can with air. 2 stage variable speed furnaces are selling well, the neatest furnace is the Rheem/Ruud modulator, with variable input from 40-100%. That's the closest forced air can come to the comfort of hydronics.


  • Warm Air Rules...The Reasons

    1) If you think about the time it takes to bring hydronics from a cold start to satisfy the t-stat, compared to the time it takes to satisfy a house heated with Warm Air.
    edge- warm air
    2)I.A.Q.- no comparison- Try treating your air with pipes.lol cant be done.
    edge-warm air
    3) Zoning- you got it, we got it. ever use a troll-a-temp..ahhh nice.
    4) Price- no brainer....
    edge-warm air
    5) Comfort- I have been in rediant houses before, just answer one question, what is the deal with panel radiators?, must be that the radiant cant keep the house warm enough. yeah, thats right, ever see back up heat on a w.a.f.????
    edge-warm air
    6)We got A.C. and you dont...haha
    Edge-Warm Air....
    In closing I must say that I did not set out to bash you guys, only to stop you from bashing warm air. The points stated above are factual and can NOT be debated!!!!!Thank you and I look foward to more waf talk here.
    Timmothy S. Plennum
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    If'n ya wants to talk warm air...

    why don't you go to a warm air web site, like Area51hvac.com???

    This place is for Wet Heads.

    Now, if'n ya wants to understand all there is to know about true comfort, hang here.



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  • ed wallace
    ed wallace Member Posts: 1,613
    warm air

    I do installs on warm air and hot water hot water is much better rads hold heat longer more comfortable than cold spots due to air blowing out of ducts

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  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490

    I'm interested in hearing his thoughts.
    Retired and loving it.
  • paul lessard_3
    paul lessard_3 Member Posts: 186
    ed wallace

    Ok Ed,I'll take back all those hostile thoughts i had about
    you (plumbers can't thoubleshoot or wire nuthin)
    Hope to see you around

    paul lessard
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    A question:

    Why does it have to be You vs. Us? Can't we learn from each other and, hopefully, raise the professionalism of the entire heating trade?
    Retired and loving it.
  • heatboy
    heatboy Member Posts: 1,468
    I am also if..........

    he can present them in a professional manner. So far, the behavior doesn't merit a discussion. I do have a query though. When trying to accomplish two diametrically opposed physics in the same duct system, which do you sacrifice? Heating or cooling? It would seem impossible to do both efficiently within the same ductwork. Also, the cold side of a structure in the Winter is never the warm side during the Summer. How do I design around these two issues. If I knew, it would be a great help since not one person has ever given me a satisfactory answer.

    Price? It's not my money. I do all the radiant I can handle. Apparently, price is secondary to my clients.

    Warm Regards,


    "Expert in Silent Warmth"™

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    The Radiant Whisperer

    "The laws of physics will outweigh the laws of ecomomics every time."
  • Mark J Strawcutter
    Mark J Strawcutter Member Posts: 625
    some debate

    > 1) If you think about the time it takes to bring

    > hydronics from a cold start to satisfy the

    > t-stat, compared to the time it takes to satisfy

    > a house heated with Warm Air. edge- warm

    > air

    I agree - if you like wild temp swings from cold to warm then hot air has an edge. But if you like nice, even heat...

    > 2) I.A.Q.- no comparison- Try treating your

    > air with pipes.lol cant be done. edge-warm

    > air

    air-to-air heat exchanger does not depend on warm air heating system. Same for humidifier - if it's even necessary.

    > 3) Zoning- you got it, we got it. ever use a

    > troll-a-temp..ahhh nice. edge-even

    hardly even - how do you give me room-level zoning with forced air?

    > 4) Price- no

    > brainer.... edge-warm air

    sorry - the price differential between a *properly designed and installed* system of each type isn't that far off. Ever price properly designed, sealed and insulated tinwork?
    On the flip side - you can install a crappy hydronic system for the same price as a crappy forced air system.

    > 5) Comfort- I have

    > been in rediant houses before, just answer one

    > question, what is the deal with panel radiators?,

    > must be that the radiant cant keep the house warm

    > enough. yeah, thats right, ever see back up heat

    > on a w.a.f.???? edge-warm air

    panel radiators _are_ radiant. The houses you've been in must have been designed with radiant sources in multiple locations (ie floor and walls) to provide nice, even warmth over a wide range of operating conditions. Ever try that with forced air? Let's see - variable speed blower, full perimiter discharge - oops, there went the budget.

    > 6)We got A.C. and

    > you dont...haha Edge-Warm

    > Air.... etc,etc,etc.

    I've lived in both forced air and hydronically heated houses that both had A/C. Both had A/C systems separate from heating systems. Trying to design a ducting system that does both heating and cooling well is a loosing battle. You end up with one that does both equally poorly.

    > In closing I must say that

    > I did not set out to bash you guys, only to stop

    > you from bashing warm air. The points stated

    > above are factual and can NOT be

    > debated!!!!!

    Oops - forgot to read this far before writing. I guess this makes my "debate" invalid, eh? :-)

    > Thank you and I look foward to more

    > waf talk here. Timmothy S. Plennum Yonkers,N.Y.

    Every now and then I forget myself, but "do not feed the trolls".

  • Bill Clinton
    Bill Clinton Member Posts: 75
    You're on

    The quintessential difference between radiant heat and forced air is in the way heat is delivered. Both heat air AND objects in the room (including human bodies.) Of necessity, and almost by definition forced air favors heating the air over objects. Radiant heat can and does make favor objects (and human bodies). Thus, you can be comfortable in a radiantly heated space with lower air temperatures. My own experience and that of almost everyone I've talked to over many years is that the radiant ambience feels much nicer.

    Also, I'd dispute the claims for quicker heat-up from forced air. The fact that forced air heats air fast doesn't mean the room is warm: it takes time to get the MRT up also. A low mass radiant heating system can warm the place just as fast.

    Finally, you gotta admit you're prejudiced. I mean: how can a tin knocker with Plennum for a last name be objective about radiant heat? Gotta bias you or my name isn't Bill Clinton:)
  • Boilerpro
    Boilerpro Member Posts: 410
    A one to one response to the reasons

    1) Yes, hot air brings the air temp up much quicker, which causes much more uneven heating as air temperature changes quickly with the cycling of equipment. Hydronics edge... How often is this important, usually once or twice a day if the homeowner setsback temps. 2) IAQ. What's probably the biggest source of indoor air quality problems...ductwork. Hydronics edge. There's no way of getting around living in your heating system with forced air, unless you use hot air radiant. 3) Zoning. Yes we both have it. However what happens when only a few rooms are running off a single big furnace... Lots of stress on heat exchanger and equipment short cyling. Hot water has the same problems with low mass systems, but the fix is too just add more mass (water). What's the fix for hot air? Hydronics edge. 4) Price. Looking at equipment costs only, here's what I see. Whats the typical life of a hot air furnace? I've been told about 10 to 15 years. Decent hot water boiler....30 years plus. Add to this humidifiers, filters, the need for duct cleaning about every 10 years, several ignitors, a few circuit board replacements, and then how does the cost stack up....Probably even.
    5)Comfort... Can't really talk about this one, you have to experience it.
    6) A/C. Hot air rises, cold air falls. How do you design your single ductwork system for both? Vents at ceiling, great comfort for the summer and great A/C efficiency, cold feet in the winter and terrible heating efficiency. Vents at floor...Warmer feet in the winter, cold feet and hot heads in the summer. Single ductwork systems rarely work efficiently and comfortable for both. No edge for either system.... cooling should be a separate system! (just take a look at some of the radiant cooling system in Europe if you want to see water cooling systems at thier best).

    Keep the challenges coming Tim! This helps us all sharpen our understanding, skills, and slaes techniques!

  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    And that last statement

    is one of the reasons why I welcome him. Hopefully, he can be as civil as you have been when answering.
    Retired and loving it.
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    I stand...

    (actually sit) corrected. I still think he's just yanking our collective proverbial chains, but in the interst of seeing a debate flow, I'll sit back and watch. Just seems funny discussing forced air on a hydronic/steam web site.

    Sorry Dan.


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  • I'm no warm air expert

    But one of the installers I work with had warm air in his house , and even with a humidifier his family woke up alot with stuffed , and sometimes bloody noses . He switched to a combo of radiant in a few rooms and baseboard in others - the problem is gone .

    One of the " non debatable " facts you might have wrong is that you need supplemental heat with radiant . My 50 + year old copper radiant had no problem keeping my home nice and toasty and draft free - even when the temp outside went below zero .

    One thing I would like to see is the cost of heating a house with warm air compared to other types of heat .
  • Bill NTSG
    Bill NTSG Member Posts: 321
    I spent

    a year and a half working for a sheetmetal contractor installing systems in new high end homes. I had to quit because it made me uncomfortable causing the structural damage to the home in order to install the ductwork. Almost all residential homes are heated with tubing less than one inch in diameter. Duct work ? 16x20 , 3-1/2 x 14 , 7" round. It takes up a lot of room. Noise. I can not hear my radiant in floor heat or my panel radiators. Well maybe a little expansion noise on start up but with constant circulation no noise and even heat. I'll bet a 3/4 hp blower fan uses more electricity than .75amp taco 007. You ever go outside and feel a breeze? We call that wind chill effect. Ever sit next to a return or supply grill ? I would call that wind chill also. Fiber duct board? YICK! Come to think of it the only thing I miss in my house that used to be FWA is a place to dry my boots. I used to put them on top of the floor register to dry. Yep thats the only thing I miss
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
    Can't be debated???

    1) If you think about the time it takes to bring hydronics from a cold start to satisfy the t-stat, compared to the time it takes to satisfy a house heated with Warm Air. Edge warm air.

    The time it takes a FA system to satisfy the THERMOSTAT is different than the time to satisfy the house! With a cold start in a cold space the FA system will shut down WAY before the hydronic--BUT the space is not really satisfied. The FA system will cycle rapidly until the warm air it creates finally heats the objects in the space. The FA has to shut down prematurely to keep the air temp of the space from fluctuating too greatly. The hydronic system will take much longer to raise the temp because it's raising the temp of everything--not just the air. That warm air "edge" diminishes greatly when you consider this! If you have massive old iron radiators (or radiant with panels) this "edge" nearly disappears.

    2)I.A.Q.- no comparison- Try treating your air with pipes.lol cant be done. edge-warm air.

    There are many aspects of IAQ. Some factors in IAQ are decidedly better with hydronics: Less air movement = less suspended dust in the air. My home gets dusty MUCH quicker when the A/C is running than when the hydronic heat is on.
    Homes with hydronics don't require as much (or any) humidification. When only modest amounts are needed and if you're lucky enough to have standing rads, you can supply the need with pans of water on a couple rads--try that with FA! If you need mechanical humidification/dehumidification, the natural tendency of humidity to stabilize throughout a structures makes stand-alone units effective and easy to care for.
    A cracked HX in a forced system WILL put CO throughout the home--impossible with hydronics.
    If "nasties" somehow grow in the heat distribution system of a closed hydronic system, they CAN'T hurt the occupants--not so for "nasties" growing in the ducts!
    When I first turn on FA heat, I open the windows and leave the place for hours--the smell of the crap burning off the HX gives me a near-instant headache--NO, I DON'T have migraines and only very rare headaches--all brought on by smells that I avoid. While there is a bit of the same smell right around the boiler when I first turn it on, I only have to leave it's immediate vicinity.

    I say the "edge" goes to hydronics. If the structure is so tight as to require fresh air, such a system can be (and I believe is best) instituted separately--there is no need for inlets/outlets in every room. It should be linked to any exhaust from the structure (bath/kitchen fans, etc.)--not to recirculating ductwork.

    3) Zoning- you got it, we got it. ever use a troll-a-temp..ahhh nice. edge-even

    Try independent zoning of each and every room (including baths) in a single F/A system. Yea, sure... FA zoning is quite limited and even then not particularly long-lived nor effective. How many times have you seen the returns of a zoned residential FA system dampered like the supplies? I bet zero. Some even "dump" their excess heat into halls/basements etc. where at best it leads to temperature imbalances and at worst utter waste. This makes a bad situation (pressurization/temperature imbalances) even worse.
    The edge is only "even" if the hydronic zoning is just as sloppy as the air...and it's hard to do it that poorly.

    4) Price- no brainer.... edge-warm air.

    Initial cost is only a portion of price.

    5) Comfort- I have been in rediant houses before, just answer one question, what is the deal with panel radiators?, must be that the radiant cant keep the house warm enough. yeah, thats right, ever see back up heat on a w.a.f.???? edge-warm air

    The room I'm currently in is currently 67.5° I'm in a short-sleeve shirt, relatively inactive and very comfortable from head-to-toe. It's in the mid-30s outside and my 75 sq.ft. EDR cast iron rad is about 88°. There is NO air movement and I'm perfectly comfortable. Except when the solar gain through the West window outpaces heat loss, this temperature does not vary by more than 1/2°.
    This room also has FA heat for use during moderate weather. I have to keep the ceiling fan running on low, and the thermostat higher to have the same level of comfort--yet my feet are almost always in a cool draft...

    Try finding ANYONE who left (or replaced) a reasonably functioning hydronic system who says "Oh, this warm air is much more comfortable."

    Those panel rads you see in a radiantly heated space are there for GOOD reason. For optimum comfort, there is a definite limit to the temp of the floor--if you need more heat in the space you must use some other source. It's not that radiant CAN'T heat the space alone, it's that it must be used properly for optimum comfort.

    Winter guests (used to FA heat) to my home invariably comment on the comfort of the rads. They LOVE the "just warm" bathroom floors and the ability to "cozy up" to a warm rad when coming in from the cold. I've never seen anyone "cuddle" with a heat register.

    I see back-up heat with FA all the time--haven't you heard of heat pumps?

    Comfort edge 100% to hydronics! I could conceivably conceed everything else--but NEVER comfort.

    6)We got A.C. and you dont...haha Edge-Warm Air....

    BUT combined air heat/cool systems are optimized either for heat OR A/C. Rarely is the heat/cool requirement proportional in each space of a system. Rarely is the heat/cool requirement across the seasons proportional. In many areas of the US the ducts are either wildly oversized for either heat or cool or somewhat inadequate to one. For it to work its best, A/C should be delivered (and returned) from high in the room, while heat delivered (and returned) from low. The occasional FA system has hi/lo returns but it's certainly not the norm. Granted FA can do both, BUT a single system cannot do both well--sorry--one exception--high pressure systems in areas with LOW heat requirement can do both well--BUT the level of engineering required for these systems intimidates many who work with air...

    Hydronics don't get distribution loss from leaks. Hydronics don't suck dirty unconditioned air in through windows/recessed light fixtures, basements--or force conditioned air out through them either. Hydronics don't get that "problem" with "cold 70." In fact, "cold 70" only exists BECAUSE of warm air. If you don't believe that, read any good heating text written immediately after WWII. A proper hydronic system is only felt--rarely/never heard. Even the best FA systems exhibit these problems to some degree, yet they only occur in the worst of hydronic systems.

    I have no doubt that FA will continue to be the heat of choice for most in the US. Why? More than anything it's because of initial price. Yes, hydronics is more expensive than FA--more expensive yet if you need A/C. It can be extraordinarly expensive with complete zoning, separate air and the finest design & materials.

    Just as there are good forced air systems, there are bad hydronic systems. BUT, when price is the real consideration and it's very easy to make a sloppy forced system work adequately, these will be the norm.

    If hydronic systems were crafted with the same attention to detail as many? most? forced air systems they simply wouldn't work.

    The forced systems I see in new homes around here still have joist bay/stud cavity (sometimes exterior & insulated) returns. Structural elements are still routinely butchered--particularly for returns. ANY DOUBLE PLATE IS A STRUCTURAL ELEMENT!!!!!!!!! Fit and finish are somewhere between poor and terrible--if you're lucky things are "sealed" with tape. Maybe the new aluminum tape will be better than old duct tape, but it sure tears easily over rough edges and I hope condensation from A/C doesn't loosen the adhesive anymore...

    A few actually appear to have been engineered as a system with carefully planned and sized ducts. Even in this case, I'd wager that the design came from someone else and may or may not be suitiable to the local climate. Most appear sized by the "this should be big enough" method using stock material. Balance in these systems relies more on air movement through the home because of pressure imbalances and velocity than on careful design.
  • Jackchips
    Jackchips Member Posts: 344
    As someone

    who lives in a house that went from radiant, something that was taken for granted, to warm air (not hot) it was a welcome change to read so many positive comments and not the negatives that are so easy to dispense. Mr. Plennum is wrong about which is better but right on with some of his points. I also hope he continues the discussion and many of you fine Wetheads continue to inform in the many positive ways available to refute his arguments.
  • Don_2
    Don_2 Member Posts: 47

    What everyone has mention to you,should not come as a
    surpise.If you do a lot of force air then you of all people
    should know that they are being completely honest.
    The Question is are you going to use this to your advantage
    or are you going be like so many who refuse to change.
    Change is good and profitable.

    Look at it this way,how many of us who were installing boilers with the circulator on the return side and thought that we were doing it right.Until this guy comes along and shows us this pumping away idea.Boy I wonder how much heat
    he took from guys who was to set in there ways And could not be convenice,that there always a better way.

  • Install a hydronic boot dryer

    That's what I did, an old 12inch by 24 inch by 18 inch high cast iron radiator. We put boots and gloves on a wire shelf two inches above rad and hang coats on hangers just above.
    The rad also heats the basement. Try that with a 3 1/4 by 14!
  • RB_2
    RB_2 Member Posts: 272

    5.1 Introduction
    Thermal comfort is that condition of mind that expresses satisfaction with the thermal environment.
    There are large variations, both physiologically and psychologically, from person to person, which
    makes it difficult to satisfy everybody in a space. The environmental conditions required for comfort
    are not the same for everyone. However, extensive laboratory and field data have been collected
    which provide the necessary statistical data to define conditions which a specified percentage of
    occupants will find thermally comfortable. Section 5 of this standard is used to determine the thermal
    environmental conditions in a space which are necessary to achieve acceptance by a specified
    percentage of occupants of that space.
    There are six primary factors that must be addressed when defining conditions for thermal comfort. A
    number of other, secondary factors affect comfort in some circumstances. The six primary factors are
    listed below. Complete descriptions of these factors are presented in Section 5.4 and Appendixes A
    and B.
    1) Metabolic rate.
    2) Clothing insulation.
    3) Air temperature.
    4) Radiant temperature
    5) Air speed.
    6) Humidity .

    ..............that's from ASHRAE Standard 55.

    Now I could go into a whole bunch of techno mumbo jumbo if you like...short strokes...comfort conditioning is not air conditioning..but they are directly related.

    We have said before...hybrid systems are the future because air and water systems are integral parts of meeting any defintion of comfort.


  • marc
    marc Member Posts: 203
    the # 1 reason

    why are all of you waisting your time on this guy. sounds like he is losing more f/a to radiant. (still only 10-15 %) of the market. keep up the good work wetheads. marc
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,490
    We're not wasting time.

    We're having a conversation with him. He's a guest in my house and we're civil to each other here. Thanks.
    Retired and loving it.
  • Jeff Lawrence_24
    Jeff Lawrence_24 Member Posts: 593

    Forced air does heat the home, but how well?

    Take a look at these attachments. They tell you the temp spread form the ideal heating curve to the radiant and forced air curve.

    My bride's feet seem to be always cold. What do you think would be better for her and everyone?
  • Alan Muller
    Alan Muller Member Posts: 31

    Can you post similar curves for standing radiation and baseboard? (I like radiators but generally find there is a lot of stacking unless a ceiling fan is running....)

  • Alaska Joe
    Alaska Joe Member Posts: 37

    I'ld love to converse with you your ideas on forced air, but my throat is to dry, and I'm too busy scratching, to be able to converse long enough. Had not the humidifier float failed and flooded the downstairs, I would be able to afford to go see the family doctor (he's plum full up of chickens this month). On the brighter side, we get much amusement from drawing pictures in the dust.And sometimes we even get JR. to make enough noise to drown out that damn blower fan squeeeel. The wife was just asking the other day if it was possible to install some grow lightes in the duct work to see what exactly was growing around the dead mouse carcasses. My wife likes our forced air furnace because when we go to bed at night, we know if our teens try sneaking a smoke inside the trailer, I mean house. (She also likes the ability of listening in on their conversations too)We found out that living with a 'cracked heat exchanger' (what that serviceman calls it every month)has helped us to save a bundle on our 'party favours'(you know what I mean!) I am the 'Man' of this house, and only I get to touch that thermostat! If somebody else is to damn hot, let'em open a window, because, forced air don't freeze!
  • I new construction

    in the Philadelphia, South Jersey area, the design of the system is left up to the low bid HVAC contractor. Most systems are just put together on site.
    I was asked by a good friend to install his system (hot air, I could not convince him, he grew up with hot air)the builder made an exception. He was given a $4500 credit by the builder. My frind had walked in on the HVAC contractor roughing in his cuts with a chain saw! He freaked out.
    The total install price was about $14,000, the builder told him I was ripping him off. His neighbors asked him how he scored a 14 seer cooling system with a 92% 2 stage gas furnace, 2 stage digital tstat, General AC-1 filter system, and no flex duct. This is not hydoronics but he loves it! P. S. he did get a deal. The builders brother asked for a card he's building a house and doesn't think he will use his contractor.
  • Mark J Strawcutter
    Mark J Strawcutter Member Posts: 625
    I must be unusual

    although my wife would probably agree that I am :-)

    Our house is far from an expensive McMansion. Paid $91k for it 2 years ago. 20 year old split entry in a development here goes for 100-110k. Hot water heat with cast iron radiators. Added SpacePak A/C right after we moved in.

    Previous house was scorched air. Duct system not suited to A/C so we installed a separate system with AHU in attic. Everyone wanted/wants to know how we manage to keep the second floor so cool (current and previous houses).

This discussion has been closed.